ANATOMY (Avaroμjj), signifying literally dissection, or separation of parts by cutting, applied to organized bodies, is used to denote the artificial separation of their component parts in order to obtain an exact knowledge of their situation, shape, and structure.

A more just idea of the nature and objects of anatomy may be given by defining it as that science, the province of which is to ascertain the structure of living and organized bodies.

All the objects of the material world may be arranged in two great divisions, according as they are organized or void of organization. Inorganic bodies (corpora bruta) are distinguished by the homogeneous characters of their internal structure, any one portion of which, in the same mass, presents the same appearance and properties as any other. Endowed also with the general properties of matter, as weight, cohesion, impenetrability, and atomic attraction, or that resident in the constituent particles, they are subject to physical laws only. All the changes which inorganic bodies undergo consist either in mechanical changes of place or shape, or in change of chemical constitution; and the consideration of the mode in which these changes take place, of the agents by which they are effected, and the laws by which they are regulated, constitutes the sciences of Mechanics and Chemistry.

In organic bodies (corpora organica, c. viva), on the contrary, we recognise a peculiar structure, in which the parts, though arranged in a certain order, are heterogeneous, or consist of different kinds of matter. In other words, not only do organized bodies consist of different kinds of substance, but these component substances may be again resolved into material elements, differing from each other in mechanical, chemical, and vital properties.

Observation further shows, that organic are distinguished from inorganic bodies by the presence of a series and combination of actions and processes, which are collectively known under the abstract denomination of Life. Of this term, however familiar it may appear, it has been found difficult to give a satisfactory arid unobjectionable definition; and physiological authors have found it requisite, in order to avoid obscurity, to define it from its tendency, its obvious effects, or, negatively, from what experience shows to ensue upon its termination. Life is an attribute of living bodies, and is known only as it manifests its presence in these; and hence, instead of saying what it is, we are compelled to specify only the circumstances which denote its existence. Attentively considered, all the varieties of organized and living bodies may be said to be distinguished from those which are inorganic by two great characters,—growth or the reproduction of the individual, and generation or the reproduction of the species. Growth, or increase of size, includes the general processes of assimilation and nutrition, with all the subordinate actions of which these are composed; and since it consists in the conversion of brüte or inorganic into living or organic matter, it constitutes one of the most essential characters of life and organization. By virtue of this, living bodies are the seat of an incessant change in their interior structure; whereas inorganic bodies remain in the same state, unless from the operation of chemical laws. The formation of a new body similar to others of the same class, order, and kind, however various in its mode, is also a uniform attribute of all living and orga[7:2:685]nized bodies. To one or other of, these two general purposes, then, all the actions and processes of living bodies, however complex and multifarious they seem, may be ultimately referred. To these two characters of living bodies Cuvier adds a third,—death, or the termination of life; but as this is a negative circumstance, and is included in the idea of life as a process having beginning and end, it is superfluous in the general idea of the term. The knowledge of the actions and processes of living and organized bodies, and of the laws to which they are subject, constitutes the science of Physiology, or, as it has been also denominated, Zoonomy (ζωη and vομoς, laws of life,) or Biology (β ∣ ος and λογoς, doctrine of life).

Life supposes organization or the arrangement of matter and material particles peculiar, to living bodies; and, reciprocally, organization, though not the cause of life and living processes, invariably implies their existence, either present or previous. In other words, every organized body either is or must have been living; and every living body is endowed with the peculiar internal structure termed organic. Though it is difficult to specify by definition the characters of this structure, some idea of it may be communicated by stating, that all living bodies possess material Organs of definite shape, substance, and structure, consisting of certain parts, and placed in proper positions. While it is the province of Physiology to study the actions and processes of living bodies, and to investigate the laws by which they are regulated, the exclusive object of Anatomy is to distinguish and describe their constituent parts,—to determine the shape, position, and structure of their organs,—and, in short, to develope their structure. The term is not free from objection, since it literally denotes one only of the means employed to acquire the information requisite. But the objection is not obviated by the substitution of such terms as morphology and organology, in so far as the study of anatomy is not confined either to the shapes of parts or the knowledge of organs alone, but considers their position, their intimate structure, and their organization; in short, all the circumstances relating to the material constitution of living bodies.

All living and organized bodies, though agreeing in the general character of possessing organs for assimilation and nutrition, and organs of reproduction, differ nevertheless in the possession or the want of organs for two other functions, viz. those for recognising the presence of foreign bodies, or organs of sensation, and those for changing place, or organs of locomotion. The possession of these organs· distinguishes those living beings denominated animals ; the want of them, in like manner characterizes those termed plants or vegetables. Upon this principle anatomy, or the science of organic structures, resolves itself into two great divisions,— Animal Anatomy, or Zootomy (ζωov and τομιf), the object of which is the investigation of the structure of animal bodies; and Vegetable Anatomy, or Pnytotomy (φorov and rομη), the object of which is to explain the structure peculiar to the vegetable tribes.

Animal anatomy, again, naturally resolves itself into several divisions, according as the object is to explain the structure of the animal kingdom at large, or that of certain classes, orders, tribes, families, or genera only. The most, ordinary and convenient division, however, is into that which treats of the anatomy of the known animal tribes in general, and that which treats of the structure peculiar to the human subject. The accidental circumstance of the former being studied chiefly in comparison with the latter, the organic forms of which are regarded as the standard of reference, has given it the denomination of Comparative Anatomy, though that of Animal Anatomy or Zootomy would be more appropriate. The latter has generally been named Anatomy simply, or the Anatomy of the Human Body, and occasionally Anthropotomy or Human Anatomy.

The connection which subsists between the latter and the several divisions of the art of healing, renders it interesting to the medical, the surgical, and the philosophical reader generally, and invests it with the highest importance to all. Comparative Anatomy, nevertheless, possesses the peculiar advantage of directing the mind of the inquirer to general resemblances, to universal facts, and to comprehensive analogies. Independent of the important services, which its knowledge renders to several of the arts, it is of the greatest use in throwing light on some of the obscurest parts of physiology; by the extensive chain of analogical facts which it traces, it tends to explain difficulties in organization and function, which could not otherwise be intelligible; and by establishing the connection between external characters and habits with peculiarities of internal structure, it affords the only rational basis for the classifications and distinctions of zoology. Comparative or Animal Anatomy constitutes the great source of what may be termed the Philosophy of Animal Life.

Of the present treatise, the greater part will be devoted to the subject of Human Anatomy, or the explanation of the structure of the human frame in the healthy state. In a smaller proportion, it is proposed to give a view of the structure of animal bodies generally, with occasional observations on those peculiarities in configuration and structure which distinguish classes, orders, and genera, from each other. This will constitute Comparative Anatomy.

In a separate article, devoted to Vegetable Anatomy, the peculiarities of structure observed in plants will be unfolded.

Previous to entering on the subject of Animal Anatomy, however, and its two divisions, Human and Comparative Anatomy, it is requisite to take an historical view of the progress of the science from its origin to the present time.

In tracing the history of the origin of anatomy, it may be justly said that more learning than judgment has been displayed. Some writers claim for it the highest antiquity, and pretend to find its first rudiments alternately in the animal sacrifices of the shepherd kings, the-Jews, and other ancient nations; and in the art of embalming, as practised by the Egyptian priests. Even the descriptions of wounds in the Iliad have been supposed adequate to prove that, in the time of Homer, mankind had distinct notions of the structure of the human body. Of the first, it may be said that the rude information obtained by the slaughter of animals for sacrifice does not imply profound anatomical knowledge; and those who adduce the second as evidence, are deceived by the language of the poet of the Trojan war, which, distinguishing certain parts by their ordinary Greek epithets, as afterwards used by Hippocrates, Galen, and all anatomists, has been rather too easily supposed to prove that the poet had studied systematically the structure of the human frame.

With not much greater justice has the cultivation of anatomical knowledge been ascribed to Hippocrates, who, because he is universally allowed to be the father of medicine, has also been thought to be the creator of the science of anatomy. Of the seven individuals of the family of the Heracleidae who bore this celebrated name, the second, who was son of Heraclides and Phenarita, and grandson of the first Hippocrates, was indeed distinguished [7:2:686]as the author of medical observation and experience, and the first who appreciated the value of studying accurately the phenomena, effects, and terminations of disease. It does not appear, however, notwithstanding the vague and general panegyrics of Riolan, Bartholin, Le Clerc, and Portal, that the anatomical knowledge of this illustrious person was either accurate or profound. Of the works ascribed to Hippocrates, five only are genuine. Most of them were written either by subsequent authors of the same name, or by one or other of the numerous impostors who took advantage of the zealous munificence of the Ptolemies, by fabricating works under that illustrious name. Of the few which are genuine, there is none expressly devoted to anatomy; and of his knowledge on this subject, the only proofs are to be found in the exposition of his physiological opinions, and his medical or surgical instructions. From these it appears that he had some accurate notions on osteology; but that of the structure of the human body in general, his ideas were at once superficial and erroneous. In his book on injuries of the head, and in that on fractures, he shows that he knew the sutures of the cranium, and the relative situation of the bones; and that he had some notion of the shape of the bones in general, and of their mutual connections. Of the muscles, of the soft parts in general, and of the internal organs, his ideas are confused, indistinct, and erroneous. The term φ^KiZς he seems, in imitation of the colloquial Greek, to have used generally to signify a blood-vessel, without being aware of the distinction of vein and artery; and the term αgr>jg∕α, or air-holder, is restricted to the windpipe. He appears to have been unaware of the existence of the nervous chords; and the term is used by him, as by Grecian authors in general, to signify a sinew or tendon. On other points his knowledge is so much combined with peculiar physiological doctrines, that it is impossible to assign them the character of anatomical facts; and even the works in which these doctrines are contained are with little probability to be ascribed to the second Hippocrates. If, however, we overlook this difficulty, and admit what is contained in the genuine Hippocratic writings to represent at least the sum of knowledge possessed by Hippocrates and his immediate descendants, we find that he represents the brain as a gland, from which exudes a viscid fluid; that the heart is muscular and of pyramidal shape, and has two ventricles separated by a partition, the fountains of life—and two auricles, receptacles of air; that the lungs consist of five ash-coloured lobes, the substance of which is cellular and spongy, naturally dry, but refreshed by the air; and that the kidneys are glands, but possess an attractive faculty, by virtue of which the moisture of the drink is separated, and descends into the bladder. He distinguishes the bowels into colon and rectum (ó αgχβi).

The knowledge possessed by the second Hippocrates was transmitted in various degrees of purity to the descendants and pupils, chiefly of the family of the Heracleidae, who succeeded him. Several of these, with feelings of grateful affection, appear to have studied to preserve the written memory of his instructions, and in this manner to have contributed to form part of that collection of treatises which have long been known to the learned world under the general name of the Hippocratic writings. Though composed, like the genuine remains of the physician of Cos, in the Ionian dialect, all of them differ from these in being more diffuse in style, more elaborate in form, and in studying to invest their anatomical and medical matter with the fanciful ornaments of the Platonic philosophy. Hippocrates had the merit of early recognising the value of facts apart from opinions, and of those facts especially which lead to general results; and in the few genuine writings which are now extant, it is easy to perceive that he has recourse to the simplest language, expresses himself in terms which, though short and pithy, are always precise and perspicuous, and is averse to the introduction of philosophical dogmas. Of the greater part of the writings collected under his name, on the contrary, the general character is verboseness, prolixity, and a great tendency to speculative opinions. For these reasons, as well as for others derived from internal evidence, while the Aphorisms, the Epidemics, and the works above mentioned, bear distinct marks of being the genuine remains of Hippocrates, it is impossible to regard the book <ιao ∣ ΦυΛο; A νιώσου as entirely the composition of that physician; and it appears more reasonable to view it as the work of some one of the numerous disciples to whom the author had communicated the results of his observation, which they unwisely attempted to combine with the philosophy of the Platonic school and their own mysterious opinions.

Among those who aimed at this distinction, the most fortunate in the preservation of his name is Polybus, the son-in-law of the physician of Cos. This person, who must not be confounded with the monarch of Corinth immortalized by Sophocles in the tragic story of Oedipus, is represented as a recluse, severed from the world and its enjoyments, and devoting himself to the study of anatomy and physiology, and to the composition of works on these subjects. To him has been ascribed the whole of the book on the Nature of the Child, and most of that on Man ; both physiological treatises, interspersed with anatomical sketches. His anatomical information, with which at present is our chief concern, appears to have been rude and inaccurate, like that of his preceptor. He represents the large vessels of the body to consist of four pairs: the first proceeding from the head by the back of the neck and spinal chord to the hips, lower extremities, and outer ankle; the second, consisting of the jugular vessels (α ∣ eφαγ ∣ - rιδις), proceeding to the loins, thighs, hams, and inner ankle; the third proceeding from the temples by the neck to the scapula and lungs, and thence by mutual intercrossings to the spleen and left kidney, and the liver and right kidney, and finally to the rectum; and the fourth from the fore-part of the neck to the upper extremities, the fore-part of the trunk, and the organs of generation.

This specimen of the anatomical knowledge of one of the most illustrious of the Hippocratic disciples differs not essentially from that of Syennesis, the physician of Cyprus, and Diogenes, the philosopher of Apollonia, two authors, for the preservation of whose opinions we are indebted to Aristotle.^[1. ∏∣f∣ "Lωaι 'l<rrβj<αj, lib. iii. cap. ii. ] They may be admitted as representing the state of anatomical knowledge among the most enlightened men at that time, and they only show how rude and erroneous were their ideas on the structure of the animal body. It may indeed, without injustice, be said, that the anatomy of the Hippocratic school is not only erroneous, but fanciful and imaginary, in often substituting mere supposition and assertion for what ought to be matter of fact. From this censure it is impossible to exempt even the name of Plato himself, for whom some notices in the Timaeus on the structure of the animal body, as taught by Hippocrates and Polybus, have procured a place in the history of the science.
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Amidst the general obscurity in which the early history of anatomy is involved, only two leading facts may be admitted with certainty. The first is, that previous to the time of Aristotle there was no accurate knowledge of anatomy; and the second, that all that was known was derived from the dissection of the lower animals only. By the appearance of Aristotle, this species of knowledge, which was hitherto acquired in a desultory and irregular manner, began to be cultivated systematically and with a definite object; and among the services which the philosopher of Stagira rendered to mankind, one of the greatest and most substantial is, that he was the founder of Comparative Anatomy, and was the first to apply its facts to the elucidation of zoology. The works of this ardent and original naturalist show that his zootomical knowledge was extensive, and often accurate; and from several of his descriptions it is impossible to doubt that they were derived from frequent personal dissection.

Aristotle, who was born 384 years before the Christian era, or in the first year of the 99th Olympiad, was, at the age of 39, requested by Philip to undertake the education of his son Alexander. During this period, it is said, he composed several works on anatomy, which however are now lost. The military expedition of his royal pupil into Asia, by laying open the animal stores of that vast and little known continent, furnished Aristotle with the means of extending his knowledge, not only of the animal tribes, but of their structure, and of communicating more accurate and distinct notions than were yet accessible to the world. A sum of 800 talents, and the concurrent aid of numerous intelligent assistants in Greece and Asia, were intended to facilitate his researches in composing a system of zoological knowledge; but it has been observed, that the number of instances in which he was thus compelled to trust to the testimony of other observers, led him to commit errors in description, which personal observation might have enabled him to avoid.

The first three books of the History of Animals, a treatise consisting of ten books, and the four books on the Parts of Animals, constitute the great monument of the Aristotelian Anatomy. From these we find that Aristotle was the first who corrected the erroneous statements of Polybus, Syennesis, and Diogenes, regarding the bloodvessels, which they made, as we have seen, to arise from the head and brain. These he represents to be two in number, placed before the spinal column, the larger on the right, the smaller on the left, which, he also remarks, is by some calledßorta(aogr?j),the first time, we observe, which thisepi-thet occurs in the history. Both he represents to arise from the heart, the larger from the largest upper cavity, the smaller or aorta from the middle cavity, but in a different manner, and forming a narrower canal. He also distinguishes the thick, firm, and more tendinous structure of the aorta from the thin and membranous structure of the vein. In describing the distribution of the latter, however, he confounds the vena cava and pulmonary artery, and, as might be expected, he confounds the ramifications of the former with those of the arterial tubes in general. While he represents the lung to be liberally supplied with blood, he describes the brain as an organ almost destitute of this fluid. His account of the distribution of the aorta is wonderfully correct. Though he does not notice the coeliac, and remarks that the aorta sends no direct branches to the liver and spleen, he had observed the mesenteric, the renal, and the common iliac arteries. It is nevertheless singular, that though he remarks particularly that the renal branches of the aorta go to the substance and not the pelvis (×οfha) of the kidney, he appears to mistake the ureters for branches of the aorta.

Of the nerves (vεuga) he appears to have the most confused notions. Making them arise from the heart, which he says has nerves (tendons) in its largest cavity, he represents the aorta to be a nervous or tendinous vein (νευξωδης <fKzZς). By afterwards saying that all the articulated bones are connected by nerves, he makes them the same as ligaments; while the character of divisibility in the long direction identifies them rather with tendons; and the assertion that no part destitute of them has sensation, makes them approach to the nervous chords of the modern anatomists. He distinguishes suet, fat, and marrow, from each other; and though he admits the spinal chord to consist of the latter substance, he differs from those authors who regard the brain of the same nature, because while brain is cold, marrow is hot.

He distinguishes the windpipe or air-holder (agr?;g/a) from the oesophagus, because it is placed before the latter, because food or drink passing into it causes distressing cough and suffocation, and because there is no passage from the lung to the stomach. He knew the situation and use of the epiglottis, seems to have had some indistinct notions of the larynx, represents the windpipe to be necessary to convey air to and from the lungs, and appears to have a tolerable understanding of the structure of the lungs. He repeatedly represents the heart, the shape and site of which he describes accurately, to be the origin of the blood-vessels, in opposition to those who made them descend from the head; yet, though he represents it as full of blood, and the source and fountain of that fluid, and even speaks of the blood flowing from the heart to the veins,^[2. £» τn>- xaįSia; γa,1 ιπηχιτιώτα; si; τα; φλιβα;. Αυτaι γaζ ιx τη; xaįĩia; ⅛χowaι to a'μa. (Tlth ~Lωωv Mθξiωr, lib. iii. cap. iv. v.) ] and thence to every part of the body,^[3. ovnrraμtvωv Si τ⅛> μooιωv τtυ α'ιματο;, xa¢avio uπoμιv, ιυλογω; ⅞ των φλιβωv ρυσι; S∕α παντο; του τωματο; arιφυxt. ΐιι l γa > και το αίμα S<α ∙rawot xaι ∙itij παν ιιναι, ιιτιο των μoζivw tκarrov ιχ τουτου συvιστr xiv. ιοιχι S’ ωroriζ ιν τι τοι; χηποι; al i>Sζaγωγιaι ×aτa<rxsυaζowaι απο μια; αζχη; και τηγηί, W πολλου; ο^ιτου; χαι άλλου; am πζο; το παντη μιταΰίϊοναι. (Ibid. lib. iii. cap. v.) ] he says nothing of the circular motion of the blood.

The diaphragm he distinguishes by the name διαζωμα, and ∙δποζωμa. With the liver and spleen, and the whole alimentary canal, he seemswell acquainted. The several parts of the quadruple stomach of the ruminating animals are distinguished and named; and he even traces the relations between the teeth and the several forms of stomach, and the length or brevity, the simplicity or complication, of the intestinal tube. Upon the same principle he distinguishes the jejunum (⅛ ψrfiτις), or the empty portion of the small intestines in animals (ro εmgoι∕ ĂE¢rroľ), the caecum (τυφXον r∕ xaι oγxωδsς), the colon (roκωλov), and the sigmoid flexure (aτεvωτεgov xaι ιiλιγμivov). The modern epithet of rectum is the literal translation of his description of the straight progress (ευ0υ) of the bowel to the anus (πgωκrog)∙ He knew the nasal cavities and the passage from the tympanal cavity of the ear to the palate, afterwards described by Eustachius.

Next to Aristotle occur the names of Diodes of Carystus, and Praxagoras of Cos, the last of the family of the Asclepiadae. The latter is remarkable for being the first who distinguished the arteries from the veins, and the author of the opinion that the former were air-vessels.

Hitherto anatomical inquiry was confined to the examination of the bodies of brute animals. We have, indeed, [7:2:688]no testimony of the human body being submitted to examination previous to the time of Erasistratus and Herophilus; and it is vain to look for authentic facts on this point before the foundation of the Ptolemaic dynasty of sovereigns in Egypt. This event, which, as is generally known, succeeded the death of Alexander, 320 years before the Christian era, collected into one spot the scattered embers of literature and science, which were beginning to languish in Greece under a weak and distracted government, and an unsettled state of society. The children of her divided states, whom domestic discord and the uncertainties of war rendered unhappy at home, wandered into Egypt, and found, under the fostering hand of the Alexandrian monarchs, the means of cultivating the sciences, and repaying with interest to the country of Thoth and Osiris, the benefits which had been conferred on the infancy of Greece by Thales and Pythagoras. Alexandria became in this manner the depository of all the learning and knowledge of the civilized world; and while other nations were sinking under the effects of internal animosities or mutual dissensions, or ravaging the earth with the evils of war, the Egyptian Greeks kept alive the sacred flame of science, and preserved mankind from relapsing into their original barbarism.

These happy effects are to be ascribed in an eminent degree to the enlightened government and liberal opinions of Ptolemy Soter, and his immediate successors Philadelphus and Euergetes. The two latter princes, whose authority was equalled only by the zeal with which they patronised science and their professors, were the first who enabled physicians to dissect the human body, and prevented the prejudices of ignorance and superstition from compromising the welfare of the human race. To this happy circumstance Herophilus and Erasistratus are indebted for the distinction of being known to posterity as the first anatomists who dissected and described the parts of the human body. Both of these physicians flourished under Ptolemy Soter, and probably Ptolemy Philadelphus, and were indeed the principal supports of what has been named in medical history the Alexandrian School, to which their reputation seems to have attracted numerous pupils.

But though the concurrent testimony of antiquity assigns to these physicians the merit of dissecting the human body, time, which wages endless war with the vanity and ambition of man, has dealt hardly with the monuments of their labours. As the works of neither have been preserved, great uncertainty prevails as to the respective merits of these ancient anatomists; and all that is now known of their anatomical researches is obtained from the occasional notices of Galen, Oribasius, and some other writers. From these it appears that Erasistratus recognised the valves of the heart, and distinguished them by the names of tricuspid and sigmoid; that he studied particularly the shape and structure of the brain, and its divisions, and cavities, and membranes, and likened the convolutions to the folds of the jejunum; that he first formed a distinct idea of the nature of the nerves, which he made issue from the brain; and that he discovered lymphatic vessels in the mesentery, first in brute animals, and afterwards, it is said, in man. It is not uninteresting to observe, that he appears to have distinguished the nerves into those of sensation and those of motion.

Of Herophilus it is said that he had extensive anatomical knowledge, acquired by dissecting, not only brutes, but human bodies. Of these he probably dissected more than any of his predecessors or contemporaries. But it is almost superfluous to remind the classical reader, that the passage of Tertullian, in which he is said to have dissected 600 corpses, is not to be understood literally, and means only that he had dissected many; and that this language is employed by an author who speaks of him in terms of execration, and who evidently exaggerates in order to prejudice the reader against the anatomist. Devoted to the assiduous cultivation of anatomy, he appears to have studied with particular attention those parts which were least understood. He recognised the nature of the pulmonary artery, which he denominates arterious vein ; he knew the vessels of the mesentery, and showed that they did not go to the vena portae, but to certain glandular bodies; and he first applied the name of twelve-inch or duodenum (δωδιxaδaxnaoς) to that part of the alimentary canal which is next to the stomach. Like Erasistratus, he appears to have studied carefully the configuration of the brain; and we learn from Galen that he first compared the linear furrow at the bottom of the fourth ventricle to the cavity of a writing pen; and though like him he distinguishes the nerves into those of sensation and those of voluntary motion, he adds to them the ligaments and tendons. A tolerable description of the liver by this anatomist is preserved in the writings of Galen.^[4. Π»«« A∙VΛT0μii<,u∙> Ε-γχu1i ιrιωt, lib. VI. ] He first applied the name of choroid or vascular membrane to that which is found in the cerebral ventricles; he knew the fourth or straight sinus, which still Eears his name; he described the posterior end of the vault or fornix as the principal seat of the sensations; and to him the linear furrow at the bottom of the fourth ventricle is indebted for its name of calamus scriptorius.

The celebrity of these two great anatomists appears to have thrown into the shade, for a long period, the names of all other inquirers; for among their numerous and rather celebrated successors in the Alexandrian school, it is impossible to recognise a name which is entitled to distinction in the history of anatomy. In a chasm so wide it is not uninteresting to find, in one who combined the character of the greatest orator and philosopher of antiquity, the most distinct traces of attention to anatomical knowledge. Cicero, in his treatise De Natura Deorum, in a short sketch of physiology, such as it was taught by Aristotle and his disciples, introduces various anatomical notices, from which the classical reader may form some idea of the state of anatomy at that time. The Roman orator appears to have formed a pretty distinct idea of the shape and connections of the windpipe and lungs; and though he informs his readers that he knows the alimentary canal, he omits the details through motives of delicacy. In imitation of Aristotle, he talks of the blood being conveyed by the veins (vxnae), that is, blood-vessels, through the body at large; and, like Praxagoras, of the air inhaled by the lungs being conveyed through the arteries.

Aretaeus, though chiefly known as a medical author, makes some observations on the lung and the pleura, maintains the glandular structure of the kidney, and describes the anastomosis or communications of the capillary extremities of the vena cava with those of the portal vein.

The most valuable depository of the anatomical knowledge of these times is the work of Celsus, one of the most judicious medical authors of antiquity. He left, indeed, no express anatomical treatise; but from the introductions to his 4th and 8th books, De Medicina, with incidental remarks in his 7th, the modern reader may [7:2:689]form very just ideas of the anatomical attainments of the Roman physician. From these it appears that Celsus was well acquainted with the windpipe and lungs, and the heart; with the difference between the windpipe and oesophagus (stomachus), which leads to the stomach (ventriculus) ; and with the shape, situation, and relations of the diaphragm. He enumerates also with accuracy the principal facts relating to the situation of the liver, the spleen, and the kidneys. His description of the situation and connections of the stomach is interesting. He appears, however, to have, been unaware of the distinction of duodenum or twelve-inch bowel, already admitted by Herophilus, and represents the stomach as directly connected by means of the pylorus with the jejunum or upper part of the small intestine. His account of the rest of the alimentary canaI, though brief and cursory, is accurate; and his subsequent descriptions of diseases seated in these parts show that he had formed ideas, upon the whole very just, of the relative positions of these parts.

The 7th and 8th books, which are devoted to the consideration of those diseases which are treated by manual operation, contain sundry anatomical notices necessary to explain the nature of the diseases, or mode of treatment. Of these, indeed, the merit is unequal; and it is not wonderful that the ignorance of the day prevented Celsus from understanding rightly the mechanism of the pathology of hernia. He appears, however, to have formed a tolerably just idea of the mode of cutting into the urinary bladder; and even his obstetrical instructions show that his knowledge of the uterus, vagina, and appendages was not contemptible. It is in osteology, however, that the information of Celsus is chiefly conspicuous. He enumerates the sutures and several of the holes of the cranium, and describes at great length the superior and inferior maxillary bones and the teeth. With a good deal of care he describes the vertebrae and the ribs, and gives very briefly the situation and shape of the scapula, humerus, radius, and ulna, and even the carpal and metacarpaI bones, and then of the different bones of the pelvis and lower extremities. He had formed a just idea of the articular connections, and is desirous to impress the fact, that none is formed without cartilage. From his mention of many minute holes (mulla et tenuia foramina), in the recess of the nasal cavities, it is evident that he was acquainted with the perforated plate of the ethmoid bone; and from saying that the straight part of the auditory canal becomes flexuous, and terminates in numerous minute cavities (multa et tenuia foramina diducitur), it is inferred by Portal that he knew the semicircular canals.

Though the writings of Celsus show that he cultivated anatomical knowledge, it does not appear that the science was much studied by the Romans; and there is reason to believe, that after the decay of the school of Alexandria it languished in neglect and obscurity. It is at least certain that the appearance of Marinus during the reign of Nero is mentioned by authors as an era remarkable for anatomical inquiry, and that this person is distinguished by Galen as the restorer of a branch of knowledge which had been before him suffered to fall into undeserved neglect. From Galen also we learn that he gave an accurate account of the muscles, that he studied particularly the glands, that he discovered those of the mesentery, and that he improved much the anatomical history of the nerves. The number of the latter he fixed at seven; he observed the palatine nerves, which he rated as the fourth pair; and described as the fifth the auditory and facial, which he regards as one pair; and the hypoglossal as the sixth.

Not long after Marinus, appeared Ruffus of Ephesus, a Greek physician, who in the reign of Trajan was much attached to physiology, and as a means of cultivating this science studied Comparative Anatomy, and made sundry experiments on living animals. Of the anatomical writings of this author, there remains only a list or catalogue of names of different regions and parts of the animal body. He appears, however, to have directed the attention particularly to the tortuous course of the uterine vessels, and to have recognised even at this' early period the Fallopian tube. He distinguishes the nerves into those of sensation and those of motion. He knew the recurrent nerve. His name is further associated with the ancient experiment of compressing in the situation of the carotid arteries the pneumogastric nerve, and thereby inducing insensibility and loss of voice.

Of all the authors of antiquity, however, none possesses so just a claim to the title of anatomist as Claudius Galenus, the celebrated physician of Pergamus. This person, who was born about the 131st year of the Christian era, and lived under the reigns of Trajan, Antoninus, Commodus, and Aelius, was trained by his father Nico, whose memory he embalms as an eminent mathematician, architect, and astronomer, to all the learning of the day, and initiated particularly into the mysteries of the Aristotelian philosophy. In an order somewhat whimsical he afterwards studied philosophy successively in the schools of the Stoics, the Academics, the Peripatetics, and the Epicureans. While at the age of 17, his father, he informs us, was admonished by a dream to devote his son to the study of medicine; but it was fully two years after, that Galen entered on this pursuit, under the auspices of an instructor, whose name he has thought proper to conceal. Shortly after, he betook himself to the study of anatomy under Satyrus, a pupil of Quintus, and of medicine under Stratonicus, a Hippocratic physician, and Aeschrion, an empiric. He had scarcely attained the age of 20, when he had occasion to deplore the loss of the first and most affectionate guide of his studies; and soon after he proceeded to Smyrna to obtain the anatomical instructions of Pelops, who, though mystified by some of the errors of Hippocrates, is commemorated by his pupil as a skilful anatomist. After this he appears to have visited various cities, distinguished for philosophical or medical teachers; and, finally, to have gone to Alexaridria with the view of cultivating more accurately and intimately the study of anatomy under Heraclianus. Here he remained till his 28th year, when he regarded himself as possessed of all the knowledge then attainable through the medium of teachers. He now returned to Pergamus, to exercise the art which he had so anxiously studied, and received, in his 29th year, an unequivocal testimony of the confidence which his fellow citizens reposed in his skill, by being intrusted with the treatment of the wounded gladiators; and in this capacity he is said to have treated with success several wounds which used to be fatal. A seditious tumult appears to have caused him to form the resolution of quitting Pergamus and proceeding to Rome, at the age of 32. Here, however, he remained only five years; and returning once more to Pergamus, after travelling for some time, finally settled in Rome as physician to the emperor Com-modus.

The anatomical writings ascribed to Galen, which are numerous, are to be viewed not merely as the result of personal research and information, but as the common depository of the anatomical knowledge of the day, arid as combining all that he had learnt from the several teachers under whom he successively studied, with whatever personal study had enabled him to acquire. It is on this account not always easy to distinguish what Galen had himself ascertained by personal research, from that which [7:2:690]was known by other anatomists. This, however, though of moment to the history of Galen as an anatomist, is of little consequence to the science itself; and, from the anatomical remains of this author, a pretty just idea may be formed, both of the progress and of the actual state of the science at that time.

The osteology of Galen is undoubtedly the most perfect of the departments of the anatomy of the ancients. He names and distinguishes the bones and sutures of the cranium nearly in the same manner as at present. Thus he notices the quadrilateral shape of the parietal bones; he distinguishes the squamous, the styloid, and the mastoid portions, and the lithoid or petrous portions of the temporal bones; and he remarks the peculiar situation and shape of the wedge-like or sphenoid bone. Of the ethmoid, which he omits at first, he afterwards speaks more at large in another treatise. The malar he notices under the name of zygomatic bone; and he describes at length the upper maxillary and nasal bones, and the connection of the former with the sphenoid. He gives the first clear account of the number and situation of the vertebrae, which he divides into cervical, dorsal, and lumbar, and distinguishes from the sacrum and coccyx. Under the head Bones of the Thorax, he enumerates the sternum, the ribs (αi íŵeuga/), and the dorsal vertebrae, the connection of which with the former he designates as a variety of diarthrosis. The description of the bones of the extremities and their articulations concludes the treatise.

Though in myology Galen appears to less advantage than in osteology, he nevertheless had carried this part of anatomical knowledge to greater perfection than any of his predecessors. He describes a frontal muscle, the six muscles of the eye, and a seventh proper to animals; a muscle to each ala nasi, four muscles of the lips, the thin cutaneous muscle of the neck, which he first termed platysma myoides, or muscular expansion, two muscles of the eyelids, and four pairs of muscles of the lower jaw, the temporal to raise, the masseter to draw to one side, and two depressors, corresponding to the digastric and internal pterygoid muscles. After speaking of the muscles which move the head and the scapula, he adverts to those by which the windpipe is opened and shut, and the intrinsic or proper muscles of the larynx and hyoid bone. Then follow those of the tongue, pharynx, and neck, those of the upper extremities, the trunk, and the lower extremities successively; and in the course of this description he swerves so little from the actual facts, that most of the names by which he distinguishes the principal muscles have been retained by the best modern anatomists. It is .chiefly in the minute account of these organs, and especially in reference to the minuter muscles, that he appears inferior to the moderns.

The angiological knowledge of Galen, though vitiated by the erroneous physiology of the times, and ignorance of the separate uses of the arteries and veins, exhibits, nevertheless, some accurate facts which show the diligence of the author in dissection. Though, in opposition to the opinions of Praxagoras and Erasistratus, he proved that the arteries in the living animal contain not air, but blood, it does not appear to have occurred to him to determine in what direction the blood flows, or whether it was movable or stationary.^[5. ∏i{ι AvΛτa i α∕zΛ>v ι.γ^ιiζr l σιuv, lib. VII. ] Representing the left ventricle of the heart as the common origin of all the arteries, though he is misled by the pulmonary artery, he nevertheless traces the distribution of the branches of the aorta with some accuracy. The vena azygos also, and the jugular veins, have contributed to add to the confusion of his description, and to render his angiology the most imperfect of his works.

In neurology we find him to be the author of the dogma, that the brain is the origin of the nerves of sensation, and the spinal chord of those of motion; and he distinguishes the former from the latter by their greater softness or less consistence. Though he admits only seven cerebral pairs, he has the merit of distinguishing and tracing the distribution of the greater part of both classes of nerves with great accuracy.

His description of the brain, though derived from dissection of the lower animals, is accurate; and his distinctions of the several parts of the organ have been retained by modern anatomists. His mode of demonstrating this organ, which indeed is clearly described, consists of five different steps. In the first the bisecting membrane, z. e. the falx (μrι ∣ uγζ δ∕χgroμovda), and the connecting bloodvessels are removed; and the dissector, commencing at the anterior extremity of the great fissure, separates the hemispheres gently as far as the torcular, and exposes a smooth surface (τr,ν χωgαv rυλωδη vως oveav), the mesolobe of the moderns, or the middle band. In the second he exposes by successive sections the ventricles, the choroid plexus, and the middle partition. The third exhibits the conoid body (ΰωμα κωιwoss) or conarium, concealed by a membrane with numerous veins, meaning that part of the plexus which is now known by the name of velum interpositum, and a complete view of the ventricles. The fourth unfolds the third ventricle (τις aiaλη τρτη κοιλία), the communication between the two latter ones, the psalloid or arch-like body (ΰωμα ψaλιδouδsζ) fornix, and the passage from the third to the fourth ventricle. In the fifth he gives an accurate description of the relations of the third and fourth ventricle, of the situation of the two pairs of eminences, nates (γλoυτa) and testes (διδυμιa vel oξ-χsις), the scolecoid or worm-like process, anterior and posterior, the tendons or processes, and lastly the linear furrow, called by Herophilus calamus scriptorius. ^[6. Tliļi Ανατομικών Eγ%ιiζtirιωv, lib. IX. ] He appears not to have known the inferior recesses. Morgagni however concludes, from a passage of the 7th bookwsg∕ Δογμάτων, that he did; but after accurately examining this and others of his anatomical writings, I cannot see any good reason for admitting the inference.

In the account of the thoracic organs equal accuracy may be recognised. He distinguishes Úie pleura by the name of inclosing membrane (υμηv iκrεξωκως, membrana succingens), and remarks its similitude in structure to that of the peritoneum, and the covering which it affords to all the organs.^[7. Αλλ’ ¢ wa⅛jfe , βΛ>i oiιτωt όποτιινιται ιrα<sι tíis <rau (ωζακν; oξγatc∣s, ωs ♯ π , .1irovan>1 tkiļ'åtì, κa, iSif%Hr∣ τωs κaτω τωv φι>ιvωv. Ibid. ] The pericardium also he describes as a membranous sac with a circular basis corresponding to the base of the heart, and a conical apex; and after an account of the tunics of the arteries and veins, he speaks shortly of the lung, and more at length of the heart, which, however, he takes some pains to prove not to be muscular, because it is harder, its fibres are differently arranged, and its action is incessant, whereas that of muscle alternates with the state of rest. In the particular description of the parts of the organ he ascribes to the auricles a more cuticular structure than to the other parts; he gives a good account of the valves and of the vessels; and notices especially the bony ring formed in the heart of the horse, elephant, and other large animals.

The description of the abdominal organs, and of the [7:2:691]kidneys and urinary apparatus, is still more minute, and in general very accurate. Our limits, however, do not permit us to give any abstract of them; and it is sufficient in general to say, that Galen gives correct views of the structure and distribution of the peritoneum and omentum, and distinguishes accurately the several divisions of the alimentary canal, and the internal structure of its component tissues. In the liver, which he allows to receive an envelope from the peritoneum, he admits, in imitation of Erasistratus, a proper substance or parenchyma, interposed between the vessels, and capable of removal by suitable dissection.

His description of the organs of generation is rather brief, and is, like most of his anatomical sketches, too much blended with physiological dogmas.

This short sketch may communicate some idea of the condition of anatomical knowledge in the days of Galen, who indeed is justly entitled to the character of rectifying and digesting, if not of creating, the science of anatomy among the ancients. Though evidently confined, perhaps entirely, by the circumstances of the times, to the dissection of brute animals, so indefatigable and judicious was he in the mode of acquiring knowledge, that many of his names and distinctions are still retained with advantage in the writings of the modems. Galen was a practical anatomist, and not only describes the organs of the animal body from actual dissection, but gives ample instructions for the proper mode of exposition. His language is in general clear, his style as correct as in most of the authors of the same period, and his manner is animated. It is indeed impossible to imagine any thing so interesting as the description of the process for demonstrating the brain and other internal organs, which is given by this patient and enthusiastic observer of nature. To some it may appear absurd to speak of any thing like good anatomical description in an author who writes in the Greek language, or any thing like an interesting and correct manner in a writer who flourished at a period when taste was depraved or extinct, and literature corrupted,—when the philosophy of Antoninus, and the mild virtues of Aurelius, could do little to soften the iron sway of Lucius Verus and Commodus; but the habit of faithful observation in Galen seems to have been so powerful, that, in the description of material objects, his genius invariably rises above the circumstances of his age. Though not so directly connected with this subject, it is nevertheless proper to mention, that he appears to have been the first anatomist who can be said, on authentic grounds, to have attempted to discover the uses of organs by vivisection and experiments on living animals. In this manner he ascertained the position and demonstrated the action of the heart; and he mentions two instances in which, in consequence of disease or injury, he had an opportunity of observing the motions of this organ in the human body.^[8. ∏ioι Avaτβ∕i∕κω> lib. VII. ] In short, without eulogizing an ancient author at the expense of critical justice, or commending his anatomical descriptions as superior to those of the moderns, it must be admitted that the anatomical writings of the physician of Pergamus form a remarkable era in the history of the science; and that by diligence in dissection, and accuracy in description, he gave the science a degree of importance and stability which it has retained through the lapse of many centuries.

The death of Galen, which took place at Pergamus in the 90th year of his age, and the 193d of the Christian era, may be regarded as the downfall of anatomy in ancient times. After this period we recognise only two names of any celebrity in the history of the science,— those of Soranus and Oribasius, with the more obscure ones of Meletius and Theophilus, the latter the chief of the imperial guard of Heraclius.

Soranus, who was an Ephesian, and flourished under the emperors Trajan and Hadrian, distinguished himself by his researches on the female organs of generation. He appears to have dissected the human subject; and this perhaps is one reason why his descriptions of these parts are more copious and more accurate than those of Galen, who derived his knowledge from the bodies of the lower animals. He denies the existence of the hymen, but describes accurately the clitoris. Soranus the anatomist must be distinguished from the physician of that name, who was also a native of Ephesus.

Oribasius, who was born at Pergamus, is said to have been at once the friend and physician of the emperor Julian, and to have contributed to the elevation of that apostate to the imperial throne. For this he appears to have suffered the punishment of a temporary exile under Valens and Valentinian; but was soon recalled, and lived in great honour till the period of his death. By Le Clerc, Oribasius is regarded as a compiler; and indeed his anatomical writings bear so close a correspondence with those of Galen, that the character is not altogether groundless. In various points, nevertheless, he has rendered the Ga-lenian anatomy more accurate; and he has distinguished himself by a good account of the salivary glands, which were overlooked by Galen.

To the same period generally is referred the anatomical introduction of an anonymous author, first published in 1618 by Lauremberg, and more recently by Bernard. It is to be regarded as a compilation formed on the model of Galen and Oribasius. The same character is applicable to the treatises of Meletius and Theophilus.

The decline indicated by these languid efforts soon sunk into a state of total inactivity; and the unsettled state of society during the latter ages of the Roman empire became extremely unfavourable to the successful cultivation of science. The sanguinary conflicts in which the southern countries of Europe were repeatedly engaged with their northern neighbours, between the second and eighth centuries, tended gradually to estrange their minds from scientific pursuits; and the hordes of barbarians by which the Roman empire was latterly overrun, while they urged them to the necessity of making hostile resistance, and adopting means of self-defence, introduced such habits of ignorance and barbarism, that science was almost universally forgotten; and the art most essential to the success of military operations was either neglected or debased by the grossest ignorance. While the art of healing was professed only by some few ecclesiastics, or by itinerant practitioners, anatomy was utterly neglected; and no name of anatomical celebrity occurs to diversify the long and uninteresting period commonly distinguished as the middle ages.

Anatomical learning, thus neglected by European nations, is believed to have received a temporary cultivation from the Asiatics. Of these, several nomadic tribes, known to Europeans under the general denomination of Arabs and Saracens, had gradually coalesced under various leaders; and by their habits of endurance, as well as of enthusiastic valour, in successive expeditions against the eastern division of the Roman empire, had acquired such military reputation, as to render them formidable where-ever[7:2:692] they appeared. After a century and a half of fo- ' reign warfare or internal animosity, under the successive dynastics of the Ommiades and Abassides, in which the propagation of Islamism was the pretext for the extinction of learning and civilisation, and the most remorseless system of rapine and destruction, the Saracens began, under the latter dynasty of princes, to recognise the value of science, and especially of that which prolongs life, heals disease, and alleviates the pain of wounds and injuries. The caliph Almansor combined with his official knowledge of Moslem law, the successful cultivation of astronomy; but to his grandson Almamon, the seventh prince of the line of the Abassides, belongs the merit of undertaking to render his subjects philosophers and physicians. By the directions of this prince, the works of the Greek and Roman authors were translated into Arabic; and the favour and munificence with which literature and its professors were patronised, speedily raised a succession of learned Arabians. The residue of the rival family of the Ommiades, already settled in Spain, was prompted by motives of rivalry or honourable ambition to adopt the same course; and while the academy, hospitals, and library of Bagdad bore testimony to the zeal and liberality of the Abassides, the munificence of the Ommiades was not less conspicuous in the literary institutions of Cordova, Seville, and Toledo.

Notwithstanding the efforts of the Arabian princes, however, and the diligence of the Arabian physicians, little was done for anatomy, and the science made no substantial acquisition. The Koran denounces as unclean the person who touches a corpse; the rules of Islamism forbid dissection; and whatever their instructors taught was borrowed from the Greeks. Abu Bekr A1- Rasi, Abu-Ali Ibn-Sina, Abul-Casem, and Abu-Walid Ibn-Roschd, the Razes, Avicenna, Albucasis, and Aver-hoes of European authors, are their most celebrated names in medicine; yet to none of these can the historian with justice ascribe any anatomical merit. Al-Rasi has indeed left descriptions of the eye, of the ear and its meatus, and of the heart; and Ibn-Sina, Abul-Casem, and Ebn-Roschd, give anatomical descriptions of the parts of the human body. But of these the general character is, that they are copies from Galen, sometimes not very just, and in all instances mystified with a large proportion of the fanciful and absurd imagery and inflated style of the Arabian writers. The chief reason of their obtaining a place in anatomical history is, that, by the influence which their medical authority enabled them to exercise in the European schools, the nomenclature which they employed was adopted by European anatomists, and continued till the revival of ancient learning restored the original nomenclature of the Greek physicians. Thus, the cervix, or nape of the neck, is nucha ; the oesophagus is meri ; the umbilical region is sumen, or sumac ; the abdomen is myrach; the peritoneum is siphac ; and the omentum, zirbus.

From the general character now given, justice requires that we except Abdollatiph, the annalist of Egyptian affairs. This author, who maintains that it is impossible to learn anatomy from books, and that the authority of Galen must yield to personal inspection, informs us, that the Moslem doctors did not neglect opportunities of studying the bones of the human body in cemeteries; and that he himself, by once examining a collection of bones in this manner, ascertained that the lower jaw is formed of one piece; that the sacrum, though sometimes composed of several, is most generally of one; and that Galen is mistaken when he asserts that these bones are not single.

The era of Saracen learning extends to the 13th century; and after this we begin to approach happier times. The university of Bologna, which, as a school of literature and law, was already celebrated in the twelfth century, became, in the course of the following one, not less distinguished for its medical teachers. Though the misgovernment of the municipal rulers of Bologna had disgusted both teachers and students, and given rise to the foundation of similar institutions in Padua and Naples, —and though the school of Salerno, in the territory of the latter, was still in high repute,— it appears, from the testimony of Sarti, that medicine was in the highest esteem in Bologna, and that it was in such perfection as to require a division of its professors into physicians, surgeons, physicians for wounds, barber-surgeons, oculists, and even some others. Notwithstanding these indications of refinement, however, anatomy was manifestly cultivated rather as an appendage of surgery than a branch of medical science; and, according to the testimony of Guy de Chauliac, the cultivation of anatomical knowledge was confined to Roger, Roland, Jamerio, Bruno, and Lan-franc; and this they borrowed chiefly from Galen. For this and similar reasons, physicians were not in all instances respected by the best informed men of the age; and they fell, perhaps not altogether undeservedly, under the bitter lash of the satirical Petrarch.

In this state matters appear to have proceeded with the medical school of Bologna till the commencement of the fourteenth century, when the circumstance of possessing a teacher of originality enabled this university to be the agent of as great an improvement in medical science as she had already effected in jurisprudence. This era, indeed, is distinguished for the appearance of Mondino, under whose zealous cultivation the science first began to rise from the ashes in which it had been buried. This father of modern anatomy, who taught in Bologna about the year 131ő, quickly drew the curiosity of the medical profession, by well-ordered demonstrations of the different parts of the human body. In 1315 he dissected and demonstrated the parts of the human body in two female subjects; and in the course of the following year he accomplished the same task on the person of a single female. But while he seems to have had sufficient original force of intellect to direct his own route, Riolan accuses him of copying Galen; and it is certain that his descriptions are corrupted by the barbarous leaven of the Arabian schools, and his Latin defaced by the exotic nomenclature of Ebn-Sina, and Abu-Bekr Al-Rasi. He died, according to Tiraboschi, in 1325.

Mondino divides the body into three cavities (ventres), the upper containing the animal members, as the head, the lower containing the natural members, and the middle containing the spiritual· members. He first delivers the anatomy of the lower cavity or the abdomen, then proceeds to the middle or thoracic organs, and concludes with the upper, comprising the head, and its contents and appendages. His general manner is to notice shortly the situation and shape or distribution of textures or membranes, and then to mention the disorders to which they are subject. The peritoneum he describes under the name of siphac, in imitation of the Arabians, the omentum under that of zirbus, and the mesentery or eucharus as distinct from both. In speaking of the intestines, he treats first of the rectum, then the colon, the left or sigmoid flexure of which, as well as the transverse arch and its connection with the stomach, he particularly remarks; then the caecum or monoculus, after this the small intestines in general under the heads of ileum and jejunum, and latterly the duodenum, making in all six bowels. The liver and [7:2:693]its vessels are minutely, if not accurately examined; and the cava, under the name chilis, a corruption from the Greek xοιkη, is treated at length, with the emulgents and kidneys. His anatomy of the heart is wonderfully accurate; and it is a remarkable fact, which seems to be omitted by all subsequent authors, that his description contains the rudiments of the circulation of the blood. “Postea vero versus pulmonem est aliud orificium venae arterialis, quae portat sanguinem ad pulmonem a corde; quia cum pulmo deserviat cordi secundum modum dictum ut ei recompenset, cor ei transmittit sanguinem per hanc venam, quae vocatur vena arterialis, et vena quae portat sanguinem, et arterialis, quia habet duas tunicas; et habet duas tunicas, primo quia vadit ad membrum quod existit in continuo motu, et secundo quia portat sanguinem valde subtilem et cholericum.” The merit of these distinctions, however, he afterwards destroys, by repeating the old assertion, that the left ventriele ought to contain spirit or air, which it generates from the blood.

His osteology of the scull is erroneous. In his account of the cerebral membranes, though short, he notices the principal characters of the dura mater. He describes shortly the lateral ventricles, with their anterior and posterior cornua, and the choroid plexus as a blood-red substance, like a long worm. He then speaks of the third or middle ventricle, and one posterior, which seems to correspond with the fourth; and describes the infundibulum under the names of lacuna and emboton. The inferior recesses he appears to have omitted. In the base of the organ he remarks, first, two mammillary caruncles, the origins of the olfactory nerves, which, however, he overlooks; the optic nerves, which he reckons the first pair; the oculo-muscular, which he accounts the second; the third, which appears to be the sixth of the moderns; the fourth; the fifth, evidently the seventh; a sixth, the nervus vagus ; and a seventh, which is the ninth of the moderns.

Notwithstanding the misrepresentations into which this early anatomist was betrayed, his book is valuable, and has been illustrated by the successive commentaries of Achillini, Berenger,' and Dryander.

Matthew de Gradibus, a native of Gradi, a town in Friuli, near Milan, distinguished himself by composing a series of treatises on the anatomy of various parts of the human body. He is the first who represents the ovaries of the female in the correct light in which they were subsequently regarded by Steno.

Similar objections to those already urged in speaking of Mondino apply to another eminent anatomist of those times. Gabriel de Zerbis, who flourished at Verona towards the conclusion of the 15th century, is celebrated as the author of a system, in which he is obviously more anxious to astonish his readers by the wonders of a verbose and complicated style, than to instruct by precise and faithful description. In the vanity of his heart he assumed the title of Medicus Theoricus ; but though like Mondino he derived his information from the dissection of the human subject, he is not entitled to the merit either of describing truly or of adding to the knowledge previously acquired. He is superior to Mondino, however, in knowing the olfacient nerves.

Eminent in the history of the science, but more distinguished than any of this age in the history of cerebral anatomy, Alexander Achillini of Bologna, the pupil and commentator of Mondino, appeared at the close of the !5th century. Though a follower of the Arabian school, the assiduity with which he cultivated anatomy has rescued his name from the inglorious obscurity in which the Arabesque doctors have in general slumbered. He is known in the history of anatomical discovery as the first who described the two tympanal bones, termed malleus and incus. In 1503 he showed that the tarsus consists of seven bones; he re-discovered the fornix and the infundibulum; and he was fortunate enough to observe, the course of the cerebral cavities into the inferior cornua, and to remark peculiarities to which the anatomists of a future age did not advert. He mentions the orifices of the ducts afterwards described by Wharton. He knew the ileo-caecal valve; and his description of the duodenum, ileum, and colon, shows that he was better acquainted with the site and disposition of these bowels than any of his predecessors or contemporaries.

Not long after, the science boasts of one of its most distinguished founders. James Berenger of Carpi, in the Modenese territory, flourished at Bologna at the beginning of the 16th century. In the annals of medicine his name will be remembered not only as the most zealous and eminent in cultivating the anatomy of the human body, but as the first physician who was fortunate enough to calm the alarms of Europe, suffering under the ravages of syphilis, then raging with uncontrollable virulence. In the former character he surpassed both predecessors and contemporaries; and it was long before the anatomists of the following age could boast of equalling him. His assiduity was indefatigable; and he declares that he dissected above 100 human bodies. He is the author of a compendium, of several treatises which he names introductions (Isagogce), and of commentaries on the treatise of Mondino. Like him, he is tinged with the mysticism of the Arabian doctrines; and though he employs the Grecian nomenclature in general, he never forgets to give the Arabian terms, and often uses them exclusively. In his commentaries on Mondino, which constitute the most perspicuous and complete of his works, he not only rectifies the mistakes of that anatomist, but delivers minute and in general accurate anatomical descriptions.

He is the first who undertakes a systematic view of the several textures of which the human body is composed; and in a preliminary commentary he treats successively of the anatomical characters and properties of fat, of membrane in general (panniculus), of flesh, of nerve, of villus or fibre (filum), of ligament, of sinew or tendon, and of muscle in general. He then proceeds to describe with considerable precision the muscles of the abdomen, and illustrates their site and connections by wooden cuts, which, though rude, are spirited, and show that anatomical drawing was in that early age beginning to be understood. In his account of the peritoneum, he admits only the intestinal division of that membrane, and is at some pains to prove the error of Gentilis, who justly admits the muscular division also. In his account of the intestines, he is the first who mentions the vermiform process of the caecum; he remarks the yellow tint communicated to the jejunum by the gall-bladder; and he recognises the opening of the common biliary duct into the duodenum (quidam porus portans choleram). In the account of the stomach he describes the several tissues of which that organ is composed, and which, after Almansor, he represents to be three, and a fourth from the peritoneum; and afterwards notices the rugae of its villous surface. He is at considerable pains to explain the organs of generation in both sexes, and gives a long account of the anatomy of the foetus. He was the first who recognised the larger proportional size of the chest in the male than in the female, and conversely the greater capacity of the female than of the male pelvis. In the larynx he discovered the two arytenoid cartilages. He gives the first good description of the thymus; distinguishes the oblique situa-tioíi[7:2:694] of the heart; describes the pericardium, and maintains the uniform presence of pericardial liquor. He then describes the cavities of the heart; but perplexes himself, as all the anatomists of that age, about the spirit supposed to be contained. The aorta he properly makes to arise from the left ventricle; but confuses himself with the arteria venalis (pulmonary vein), and the vena arterialis, the pulmonary artery. His account of the brain is better. He gives a minute and clear account of the ventricles, remarks the corpus striatum, and has the sagacity to perceive that the choroid plexus consists of veins and arteries; he then describes the middle or third ventricle, the infundibulum or lacuna of Mondino, and the pituitary gland; and, lastly, the passage to the fourth ventricle, the conarium or pineal gland, and the fourth or posterior ventricle itself, the relations of which he had studied accurately. He rectifies the mistake of Mon-dino as to the olfactory or first pair of nerves, gives a good account of the optic and others, and is entitled to the praise of originality in being the first observer who contradicts the fiction of the wonderful net, and indicates the principal divisions of the carotid arteries. He enumerates the tunics and humours of the eye, and gives an account of the internal ear, in which he notices the malleus and incus.

It hgd been written in the book of the destinies, that the science of anatomy was to be cultivated first in Italy; and that the country, already so illustrious in literature, should be honoured in giving birth to the first eminent anatomists in Europe. This distinction she long retained; and the glory she acquired in the names of Mondino, Achillini, Carpi, and Massa, was destined to become more conspicuous in the labours of Columbus, Fallopius, and Eustachius. While Italy, however, was thus advancing the progress of science, the other nations of Europe were either in profound ignorance or in the most supine indifference to the brilliant career of their zealous neighbours. The sixteenth century had commenced before France began to acquire any anatomical distinction in the names of Dubois, Fernel, and Etienne; and even these celebrated teachers were less solicitous in the personal study of the animal body, than in the faithful explanation of the anatomical writings of Galen. The infancy of the French school had to contend with other difficulties. The small portion of knowledge which had been hitherto diffused in the country was so inadequate to eradicate the prejudices of ignorance, that it was either difficult or absolutely impossible to procure human bodies for the purposes of science; and we are assured, on the testimony of Vesalius and other competent authorities, that the practical part of anatomical instruction was obtained entirely from the bodies of the lower animals. The works of the Italian anatomists were unknown; and it is a proof of the tardy communication of knowledge, that while the structure of the human body had been taught in Italy for more than a century by Mondino and his followers, they are never mentioned by Etienne, who flourished long after.

Such was the aspect of the times at the appearance of Jacques Dubois, who, under the Romanized name of Jacobus Sylvius, according to the fashion of the day, has been fortunate in acquiring a reputation to which his researches do not entitle him. For the name of James Dubois, the history of anatomy, it is said, is indebted to his inordinate love of money. At the instance of his brother Francis, who was professor of eloquence in the College of Tournay at Paris, he repaired to this university, and devoted himself to the study of the learned languages and mathematics; but discovering that these elegant accomplishments do not invariably reward their cultivators with the goods of fortune, Dubois betook himself to medicine. After the acquisition of a medical degree in the university of Montpellier, at the ripe age of fifty-one Dubois returned to Paris to resume a course of anatomical instructions which had been interrupted by the canonical interference of the medical faculty. Here he taught anatomy to a numerous audience in the college of Trinquet; and, on the departure of Vidus Vidius for Italy, was appointed to succeed that physician as professor of surgery to the Royal College. His character is easily estimated. With a greater portion of coarseness in his manners and Ianguage than even the rude state of society can palliate, with much varied learning and considerable eloquence, he was a blind, indiscriminate, and irrational admirer of Galen, and interpreted the anatomical and physiological writings of that author, in preference to giving demonstrations from the subject. Without talent for original research or discovery himself, his envy and jealousy made him detest every one who gave proofs of either. We are assured by Vesalius, who was some time his pupil, that his manner of teaching was calculated neither to advance the science nor to rectify the mistakes of his predecessors. A human body was never seen in the theatre of Dubois; the carcasses of dogs and other animals were the materials from which he taught; and so difficult even was it to obtain human bones, that unless Vesalius and his fellow-students had collected assiduously from the Innocents and other cemeteries, they must have committed numerous errors in acquiring the first principles. This assertion, however, is contradicted by Riolan, and more recently by Sprengel and Lauth, the last of whom decidedly censures Vesalius for this ungrateful treatment of his instructor. It is certain that opportunities of inspecting the human body were by no means so frequent as to facilitate the study of the science. Though his mention of injections has made him be thought the discoverer of that art, he appears to have made no substantial addition to the information already acquired; and the first acknowledged professor of anatomy to the university of Paris appears in history as one who lived without true honour, and died without just celebrity. He must not be confounded with Franciscus Sylvius (De le Boe), who is mentioned by Ruysch and Malacame as the author of a particular method of demonstrating the brain.

Almost coeval maybe placed Charles Etienne, a younger brother of the celebrated printers, and son to Henry, who Hellenized the family name by the classical appellation of Stephen (Σηρανο;). It is uncertain whether he taught publicly. But his tranquillity was disturbed, and his pursuits interrupted, by the oppressive persecutions in which their religious opinions involved the family; and Charles Etienne drew the last breath of a miserable life in a dungeon in 1564. Etienne, though sprung of a family whose classical taste has been their principal glory, betrays not the same servile imitation of the Galenian anatomy with which Dubois is charged, and is the first anatomical author who deviates from the beaten path. He appears to have been the first to detect valves in the orifice of the hepatic veins. He was ignorant, however, of the researches of the Italian anatomists; and his description of the brain is inferior to that given 60 years before by Achil-lini. His comparison of the cerebral cavities to the human ear has persuaded Portal that he knew the inferior cornua, and hippocampus, and its prolongations; but this is no reason for giving him that honour, to the detriment of the reputation of Achillini, to whom, so far as historical testimony goes, the first knowledge of this fact is due. The researches of Etienne into the structure of the nervous[7:2:695] system are, howéver, neither useless nor inglorious; and the circumstance of demonstrating a canal through the entire length of the spinal chord, which had neither been suspected by contemporaries nor noticed by successors, till Μ. Senac made it known, is sufficient to place him high among the class of anatomical discoverers.

The French anatomy of the sixteenth century was distinguished by two circumstances unfavourable to the advancement of the science,—extravagant admiration of antiquity, with excessive confidence in the writings of Galen, and the general practice of dissecting principally the bodies of the lower animals. Both of these errors were much amended, if not entirely removed, by the exertions of a young Fleming, whose appearance forms a conspicuous era in the history of cerebral anatomy. Andrew Vesalius, a native of Brussels, after acquiring at Louvain the ordinary classical attainments of the day, began, at the age of 14, to study anatomy under the auspices of Dubois. Though the originality of his mind soon led him to abandon the prejudices by which he was environed, and take the most direct course for attaining a knowledge of the structure of the human frame; yet he neither underrated the Galenian anatomy, nor was he indolent in the dissection of brute animals. The difficulties, however, with which the practical pursuit of human anatomy was beset in France, and the dangers with which he had to contend, made him look to Italy as a suitable field for the cultivation of the science; and in 1536 we find him at Venice, at once pursuing the study of human anatomy with the utmost zeal, and requested, ere he had attained his 22d year, to demonstrate publicly in the university of Padua. After remaining here about seven years, he went by express invitation to Bologna, and shortly afterwards to Pisa; and Vesalius, thus professor in three universities, appears to have carried on his anatomical investigations and instructions alternately at Padua, Bologna, and Pisa, in the course of the same winter. It is on this account that Vesalius, though a Fleming by birth, and trained originally in the French school, belongs, as an anatomist, to the Italian, and may be viewed as the first of an illustrious line of teachers by whom the anatomical reputation of that country was in the course of the sixteenth century raised to the greatest eminence.

Vesalius is known as the first author of a comprehensive and systematic view of human anatomy. The knowledge with which his dissections had furnished him, proved how many errors were daily taught and learned under the broad mantle of Galenian authority; and he perceived the necessity of a new system of anatomical instruction, divested of the omissions of ignorance and the misrepresentations of prejudice and fancy. The early age at which he effected this object has been to his biographers the theme of boundless commendations; and we are told that he began at the age of 25 to arrange the materials he had collected, and accomplished his task ere he had completed his 28th year.

Soon after this period we find him invited as imperial physician to the court of Charles V., where he was occupied in the duties of practice, and answering the various charges which were unceasingly brought against him by the Galenian disciples. After the abdication of Charles, he continued at court in great favour with his son Philip II. To this he seems to have been led principally by the troublesome controversies in which his anatomical writings had involved him. It is painful to think, however, that even imperial patronage bestowed on eminent talents does not insure immunity from popular prejudice; and the fate of Vesalius will be a lasting example of the barbarism of the times, and of the precarious tenure of the safety even of a great physician. On the preliminary'· circumstances authors are not agreed; but the most general account states, that when Vesalius was inspecting, with the consent of his kinsmen, the body of a Spanish grandee, it was observed that the heart still gave some feeble palpitations when divided by the knife. The immediate effects of this outrage to human feeling were to denounce the anatomist to the inquisition; and Vesalius escaped the merciful dispensations of this tribunal only by the influence of the king, and by promising to perform a pilgrimage to the Holy Land. He forthwith proceeded to Venice, from which he sailed with the Venetian fleet, under James Malatesta, for Cyprus. When he reached Jerusalem, he received from the Venetian senate a message requesting him again to accept the Paduan professorship, which had become vacant by the death of his friend and pupil Fallopius. His destiny, however, which pursued him fast, suffered him not again to breathe the Italian air. After struggling for many days with adverse winds in the Ionian Sea, he was wrecked on the island of Zante, where he quickly breathed his last in such penury, that unless a liberal goldsmith had defrayed the funeral charges, his carcass must have been devoured by beasts of prey. At the time of his death he was scarcely 50 years of age.

To form a correct estimate of the character and merits of Vesalius, we must not compare him, in the spirit of modern perfection, with the anatomical authors either of later times or of the present day. Whoever would frame a just idea of this anatomist, must imagine himself living in the days of Charles V., when learning did not uniformly liberalize,—when the rekindling light of ancient times shone on nothing but its own glories,—when education consisted in the knowledge of ancient opinions, and the authority of Grecian and Roman names usurped in the temple of science the legitimate worship of nature. He must imagine, not a bold innovator without academical learning,—not a genius coming from a foreign country, unused to the forms and habits of Catholic Europe,—nor a wild reformer, blaming indiscriminately every thing which accorded not with his opinions ;—but a young student scarcely emancipated from the authority of instructors,and whose intellect was still influenced by the doctrines with which it had been originally imbued,—an individual strictly trained in the opinions of the time, living amidst men who venerated Galen as the oracle of anatomy and the divinity of medicine,—exercising his reason to estimate the soundness of the instructions then in use, and proceeding, in the way least likely to offend authority and wound prejudice, to rectify errors, and to establish on the solid basis of observation the true elements of anatomical science. Vesalius has been denominated the founder of human anatomy; and though we have seen that in this career he was preceded with honour by Mondino and Be-renger, still the small proportion of correct observation which their reverence for Galen and Arabesque doctrines allowed them to communicate, will not in a material degree impair the original merits of Vesalius. The errors which he rectified, and the additions which he made, are .so numerous, that it is impossible, in such a sketch as the present, to communicate a just idea of them.

Besides the first good description of the sphenoid bone, he showed that the sternum consists of three portions, and the sacrum of five or six; and described accurately the vestibule in the interior of the temporal bone. He not only verified the observation of Etienne on the valves of the hepatic veins, but he described well the vena azygos, and discovered the canal which passes in the foetus between the umbilical vein and the vena cava, since nam,- [7:2:696]ed ductus venosus. He described the omentum, and its connections with the stomach, the spleen, and the colon; gave the first correct views of the structure of the pylorus; remarked the small size of the caecal appendix in man; gave the first good account of the mediastinum and pleura, and the fullest description of the anatomy of the brain yet advanced. He appears, however, not to have understood well the inferior recesses; and his account of the nerves is confused by regarding the optic as the first pair, the third as the fifth, and the fifth as the seventh.

The labours of Vesalius were not limited to the immediate effect produced by his own writings. His instructions and example produced a multitude of anatomical inquirers of different characters and varied celebrity, but by whom the science was extended and rectified. Of these it belongs not to this place to speak in detail; but historical justice requires us to notice shortly those towhose exertions the science of anatomy has been most indebted.

The first that claims attention on this account is Bar-tholomeo Eustachi of San Severino, near Salerno, who though greatly less fortunate in reputation than Vesalius, divides with him the merit of creating the science of human anatomy. He extended the knowledge of the internal ear, by re-discovering and describing correctly the tube which bears his name; and if we admit that Ingras-sias anticipated him in the knowledge of the third bone of the tympanal cavity, the stapes, he is still the first who described the internal and anterior muscles of the malleus, as also the stapedius, and the complicated figure of the cochlea. He is the first who studied accurately the anatomy of the teeth, and the phenomena of the first and second dentition. The work, however, which demonstrates at once the great merit and the unhappy fate of Eustachius, is his Anatomical Engravings, which, though completed in 1552, nine years after the impression of the work of Vesalius, the author was unable to publish. First communicated to the world in 1714 by Lancisi, afterwards in 1740 by Cajetan Petrioli, again in 1744 by Albinus, and more recently at Bonn, in 1790, they show that Eustachius had dissected with the greatest care and diligence, and taken the utmost pains to give just views of the shape, size, and relative position of the organs of the human body.

The first seven plates illustrate the history of the kidneys, and some of the facts relating to the structure of the ear. The eighth represents the heart, the ramifications of the vena azygos, and the valve of the vena cava, named from the author. In the seven subsequent plates îs given a succession of different views of the viscera of the chest and abdomen. The seventeenth contains the brain and spinal chord; and the eighteenth more accurate views of the origin, course, and distribution of the nerves than were then given. Fourteen plates arc devoted to the muscles.

Eustachius did not confine his researches to the study of relative anatomy. He investigated the intimate structure of organs with assiduity and success. What was too minute for unassisted vision he inspected by means of glasses. Structure, which could not be understood in the recent state, he unfolded by maceration in different fluids, or rendered more distinct by injection and exsiccation. The facts unfolded in these figures are so important, that it is justly remarked by Lauth, that if the author himself had been fortunate enough to publish them, anatomy would have attained the perfection of the 18th century two centuries earlier at least. Their seclusion for that period in the papal library has given celebrity to many names, which would have been known only in the verification of the discoveries of Eustachius.

Eustachius was the contemporary of Vesalius. Columbus and Fallopius were his pupils. The former, as his immediate successor in Padua, and afterwards as professor at Rome, distinguished himself by rectifying and improving the anatomy of the bones; by giving correct accounts of the shape and cavities of the heart, of the pulmonary artery and aorta, and their valves, and tracing the course of the blood from the right to the left side of the heart; by a good description of the brain and its vessels, and by correct understanding of the internal ear, and the first good account of the ventricles of the larynx. The latter, who after being professor at Pisa in 1548, and at Padua in 1551, died at the age of 40, studied the general anatomy of the bones; described better than heretofore the internal ear, especially the tympanum and its osseous ring, the two fenestrae, and their communication with the vestibule and cochlea; and gave the first good account of the stylo-mastoid hole and canal, of the ethmoid bone and cells, and of the lacrymal passages. In myology he rectified several mistakes of Vesalius. He made some curioup researches into the organs of generation in both sexes, and discovered the utero-peritoneal canal which still bears his name.

Osteology nearly at the same time found an assiduous cultivator in John Philip Ingrassias, a learned Sicilian physician, who, in a skilful commentary on the osteology of Galen, corrected numerous mistakes. He gave the first distinct account of the true configuration of the sphenoid and ethmoid bones, and has the merit of first describing the third bone of the tympanum, called stapes, though this is also claimed by Eustachius and Fallopius. He appears also to have known the fenestrae, the chorda tympani, the cochlea, the semi-circular canals, and the mastoid cells.

The anatomical descriptions of Vesalius underwent the scrutiny of various inquirers, actuated, some by motives of hostility to the individual, others by the more honourable wish to ascertain if his representations accorded with nature. Of the latter, Fallopius was one; but the most distinguished by the importance and veracity of their researches, as well as the temperate tone of their observations, were Julius Caesar Aranzi, anatomical professor for 32 years in the university of Bologna, and Constantio Varoli, physician to Pope Gregory XIII. To the former we are indebted for the first correct account of the anatomical peculiarities of the foetus, and for being the first to show that the muscles of the eye do not, as was falsely imagined, arise from the dura mater, but from the margin of the optic hole. He also, after considering the anatomical relations of the cavities of the heart, the valves, and the great vessels, corroborates the views of Columbus regarding the course which the blood follows in passing from the right to the left side of the heart. I have already mentioned Alexander Achillini as the reputed and probable discoverer of the inferior recesses of the cerebral cavities; but whether he knew them or not, certain it is that neither his contemporaries nor successors gave any proof that they were acquainted with these regions of the brain. Aranzi is the first anatomist who describes them distinctly, who recognises the objects by which they are distinguished, and who gives them the name by which they are still known (bombyx, hippocampus) ; and his account is more minute and perspicuous than that of the authors of the subsequent century. He speaks at large of the choroid plexus, and gives a particular description of the fourth ventric!e under the name of cistern of the cerebellum, as a discovery of his own..

Italy, though rich in anatomical talent, has produced probably none greater than Constantio Varoli of Bologna, [7:2:697]Though limited in the measure of his existence to the short space of 32 years, he acquired reputation not inferior to that of the most eminent of his contemporaries. He is now known chiefly as the author of an Epistle, inscribed to Hieronymo Mercuriali, on the optic nerves, in which he describes a new method of dissecting the brain, and communicates many interesting particulars relating to the anatomy of the organ. Overlooking the fanciful comparison of the transverse eminence and the prolongations (crura) of the brain and cerebellum to a bridge over the water of an aqueduct, though he examines the lower surface of the organ with tedious minuteness, he gives evidence that he formed a more accurate and just idea of its configuration than any of the best modern anatomists. He observes the threefold division of the inferior surface or base, defines the limits of the anterior, middle, and posterior eminences, as marked by the compartments of the scull, and justly remarks that the cerebral cavities are capacious, communicate with each other, extending first backward and then forward, near the angle of the pyramidal portion of the temporal bone, and that they are folded on themselves, and finally lost above the middle and inferior eminence of the brain. He appears to have been aware that at this point they communicate with the exterior or convoluted surface. He recognised the impropriety of the term corpus callosum, seems to have known the communication, called afterwards foramen Monroianurn, and describes the hippocampus more minutely than had been previously done.

Among the anatomists of the Italian school, as a pupil of Fallopius, Eustachius, and Aldrovandus, is generally enumerated Volcher Coiter of Groningen. He distinguished himself by accurate researches on the cartilages, the bones, and the nerves, recognised the value of morbid anatomy, and made some experiments on living animals to ascertain the action of the heart and the influence of the brain.

The Frutefull and Necessary Briefe Worke of John Halle (1565), and The Englisheman’s Treasure, by Master Thomas Vicary (1586), both English works published at this time, are tolerable compilations, partly from Be-renger, partly from Vesalius, and much tinged by the Galenian and Arabian distinctions.

The celebrity of the anatomical school of Italy was worthily maintained by Hieronymo Fabricio of Aqua-pendente, who, in imitation of his master Fallopius, laboured to render anatomical knowledge more precise by repeated dissections, and to illustrate the obscure by researches on the structure of animals in general. In this manner he investigated the formation of the foetus, the structure of the oesophagus, stomach, and bowels, and the peculiarities of the eye, the ear, and the larynx. The discovery, however, on which his surest claims to eminence rest, is that of the membranous folds, which he names valves, in the interior of veins. Several of these folds had been observed by Femel, Sylvius, and Vesalius; and in 1547 Cannani observed those of the vena azygos ; but no one appears to have offered any rational conjecture on their use, or to have traced them through the venous system at large, until Fabricius in 1574, upon this hypothesis, demonstrated the presence of these valvular folds in all the veins of the extremities.

Fabricius, though succeeded by his pupil Julius Casserius of Placenza, may be regarded as the last of that illustrious line of anatomical teachers by whom the science was so successfully studied and taught in the universities of Italy. The discoveries which each made, and the errors which their successive labours rectified, tended gradually to give anatomy the character of a useful as well as an accurate science, and to pave the way for a discovery which, though not anatomical, but physiological, is so intimately connected with correct knowledge of the shape and situation of parts, that it exercised the most powerful influence on the future progress of anatomical inquiry. This was the knowledge of the circular motion of the blood,—a fact which, though obscurely conjectured by Aristotle, Mon-dino, and Berenger, and partially taught by Servetus, Columbus, Caesalpinus, and Fabricius, it was nevertheless reserved to William Harvey fully and satisfactorily to demonstrate.

I have already shown that Mondino believed that the blood proceeds from the heart to the lungs, through the vena arterialis or pulmonary artery, and that the aorta conveys the spirit into the blood, through all parts of the body. This doctrine was adopted with little modification by Berenger, who further demonstrated the existence and operation of the tricuspid valves in the right ventricle, and of the sigmoid valves at the beginning of the pulmonary artery and aorta, and that there were only two ventricles separated by a solid impervious septum. These were afterwards described in greater detail by Vesalius, who nevertheless appears not to have been aware of the important use which might be made of this knowledge. It was Michael Servet or Servetus, 1 a Spanish monk, who in his treatise de Trinitatis Erroribus, published at Basil in 1531, or, according to Sprengel, in 1552, first maintained the imperviousness of the septum, and the transition of the blood by what he terms an unknown route, namely, from the right ventricle by the vena arteriosa (pulmonary artery) to the lungs, and thence into the arteria venosa or pulmonary vein, and left auricle and ventricle, from which, he adds afterwards, it is conveyed by the aorta to all parts of the body. 2 Though the leading outlines, not only of the pulmonary ’ Bom in 1509; burnt in 1553.

* The passage of Servetus is so interesting, that our readers may feel some curiosity in perusing it in the language of the author; and it is not unimportant to remark, that Servetus appears to have been led to think of the course of the blood, by the desire of explaining the manner in which the animal spirits were supposed to be generated. “Vitalis spiritus in sinistro cordis ventriculo suam originem habet, juvantibus maxime pulmonibus ad ipsius perfectionem. Est spiritus tenuis, caloris vi elaboratus, flave colore, ignea potentia, ut sit quasi ex puriore sanguine lucens, vapor substantiam continens aqua?, aeris, et ignis. Generatur ex facta in pulmone commixtione inspirati aeris cum elaborato subtili sanguine, quem dexter ventriculus sinistro communicat. Fit autem communicatio haec, non per parietem cordis medium, ut vulgo creditur, sed magno artificio a dextro cordis ventriculo, longo per pulmones ductu agitatur sanguis subtilis; a pulmonibus praeparatur, flavus efficitur, et a vena arteriosa in arteriam venosam transfunditur. Deinde in ipsa arteria venosa, inspirato aeri miscetur, et exspiratione a fuligine expurgatur; atque ita tandem a sinistro cordis ventriculo totum mixtum per diastolen attrahitur, apta supellex, ut fiat spiritus vitalis. Quod ita per pulmones fiat communicatio et praeparatio, docet conjunctio varia, et communicatio venae arteriosae cum arteria venosa in pulmonibus. Confirmat hoc magnitudo insignis venae arteriosae, quae nec talis nec tanta esset facta, nec tantam a corde ipso vim purissimi sanguinis in pulmones emitteret, ob solum eorum nutrimentum; nec cor pulmonibus hac ratione serviret, cum praesertnn antea in embryone solerent pulmones ipsi aliunde nutriri, ob membranulas illas seu valvulas cordis, usque ad horum nativitatem; ut docet Galenus, &c. Itaque ille spiritus a sinistro cordis ventriculo arterias totius corporis deinde transfunditur, ita ut qui tenuior est, superiora petit, ubi magis elaboratur, praecipue in plexu retiformi, sub basi cerebri sito, ubi ex vitali fieri incipit animalis, ad propriam rationalis aniniae rationem accedens.” (De Trinitate, lib. v.) [7:2:698]or small, but even of the great circulation, were sketched thus early by one who, though a philosopher, was attached to the church, it was only in his work De Re Anatomica, published at Venice in 1559, that Columbus formally and distinctly announced the circular course of the blood as a discovery of his own; and maintained, in addition to the imperviousness of the septum, the fact that the arteria venalis (pulmonary vein) contains not air, but blood mixed with air brought from the lungs to the left ventricle of the heart, to be distributed through the body at large.

Soon after, views still more complete of the small or pulmonary circulation were given by Andrew Caesalpinus of Arezzo, who not only maintained the analogy between the structure of the arterious vein or pulmonary artery and the aorta, and that between the venous artery or pulmonary veins, and veins in general, but was the first to remark the swelling of veins below ligatures, and to infer from it a refluent motion of blood in these vessels. The discoveries of Aranzi and Eustachius in the vessels of the foetus, tended at first to perplex, and afterwards to elucidate some of these notions. At length it happened, that between the years 1598 and 1600, a young Englishman, pursuing his anatomical studies at Padua under Fabricius of Aquapendente, learnt from that anatomist the existence of the valves in the veins of the extremities, and undertook to ascertain the use of these valves by experimental inquiry. It is uncertain whether he learnt from the writings of Caesalpinus the fact observed by that author, of the tumescence of a vein below the ligature; but he could not fail to be aware, and indeed he shows that he was aware, of the small circulation as taught by Servetus and Columbus. Combining these facts already known, he, by a series of well-executed experiments, demonstrated clearly the existence, not only of the small, but of a general circulation from the left side of the heart by the aorta and its subdivisions, to the right side by the veins. This memorable truth was first announced in the year 1619.

It belongs not to this place, either to consider the arguments and facts by which Harvey defended his theory, or to notice the numerous assaults to which he was exposed, and the controversies in which his opponents wished to involve him. It is sufficient to say, that after the temporary ebullitions of spleen and envy had subsided, the doctrine of the circular motion of the blood was admitted by all enlightened and unprejudiced persons, and finally was universally adopted, as affording the most satisfactory explanation of many facts in anatomical structure which were either misunderstood or entirely overlooked. The inquiries to which the investigation of the doctrine gave rise produced numerous researches on the shape and structure of the heart and its divisions, of the lungs, and of the blood-vessels and their distribution. Of this description were the researches of Nicoas Steno on the structure of the heart, the classical work of Richard Lower, the dissertation of Pechlin, the treatise of Vieussens, the work of Malpighi on the structure of the lungs, several sketches in the writings of Mayow, and other treatises of less moment. Systematic treatises of anatomy began to assume a more instructive form, and to breathe a more philosophical spirit. The great work of Adrian Spigelius, which appeared in 1627, two years after the death of the author, contains indeed no proof that he was aware of the valuable generalization of Harvey; but in the institutions of Caspar Bartholin, as republished and improved by his son Thomas in 1651, the anatomical descriptions and explanations are given with reference to the new doctrine. A still more unequivocal proof of the progress of correct anatomical knowledge was given in the lectures delivered by Peter Dionis, at the Jardin Royal of Paris, in 1673 and the seven following years, in which that intelligent surgeon gave most accurate demonstrations of all the parts composing the human frame, and especially of the heart, its auricles, ventricles, and valves, and the large vessels connected with it and the lungs. These demonstrations, first published in 1690, were so much esteemed, that they underwent in the space of 30 years seven editions, were translated into English, and formed for a long time the best and only anatomical system in Europe.

The progress of anatomical discovery continued in the mean time to advance. In the course of the 16th century, Eustachius, in studying minutely the structure of the vena azygos, had recognised in the horse a white vessel full of watery fluid, connected with the internal jugular vein, on the left side of the vertebral column, corresponding accurately with the vessel since named thoracic dud Fallopius also described vessels belonging to the liver, distinct from arteries and veins; and similar vessels appear to have been noticed by Nicoaus Massa. The nature and properties of these vessels were, however, entirely unknown. On the 23d July 1622 Gaspar Asellius, professor of anatomy at Pavia, while engaged in demonstrating the recurrent nerves in a living dog, first observed numerous white delicate filaments crossing the mesentery in all directions; and though he took them at first for nerves, the opaque white fluid which they shed quickly convinced him that they were a new order of vessels. The repetition of the experiment the following day showed that these vessels were best seen in animals recently fed; and as he traced them from the villous membrane of the intestines, and observed the valves with which they were liberally supplied, he inferred that they were genuine chyliferous vessels. By confounding them with the lymphatics, he made them proceed to the pancreas and liver,—a mistake which appears to have been first rectified by Francis De le Boe. The discovery of Asellius was announced in 1627; and the following year, by means of the zealous efforts of Nicoas Peiresc, a liberal senator of Aix, the vessels were seen in the person of a felon who had eaten copiously before execution, and whose body was inspected an hour and a half after. In 1629 they were publicly demonstrated at Copenhagen by Simon Pauli, and the same year the thoracic duct was observed by Mentel for the first time since it was described by Eustachi. Five years after (1634), John Wesling, professor of anatomy and surgery at Venice, gave the first delineation of the lacteals from the human subject, and evinced more accurate knowledge than his predecessors, of the thoracic duct and the lymphatics. Highmore in 1637 demonstrated unequivocally the difference between the lacteals and the mesenteric veins; and though some perplexity was occasioned by the discovery of the pancreatic duct by Wirsung, yet this mistake was corrected by Thomas Bartholin; and the discovery by Pecquet in 1647, of the common trunk of the lacteals and lymphatics, and of the course which the chyle follows to reach the blood, may be regarded as the last of the series of isolated facts by the generalization of which the extent, distribution, and uses of the most important organs of the animal body were at length developed.

To complete the history of this part of anatomical science one step yet remained,—the distinction between the lacteals and lymphatics, and the discovery of the termination of the latter order of vessels. The honour of this discovery is divided between Jolyffe, an English anatomist, and OIaus Rudbeck, a young Swede. The former, according to the testimony of Glisson and Wharton, was aware of the distinct existence of the lymphatics in 1650, [7:2:699]and demonstrated them as such in 1652. It is nevertheless doubtful whether he knew them much before the latter period; and it is certain that Rudbeck observed the lymphatics of the large intestines, and traced them to glands, on the 27th January 1651, after he had, in the course of 1650, made various erroneous conjectures regarding them, and, like others, attempted to trace them to the liver. The following year he demonstrated them in presence of Queen Christina, and traced them to the thoracic duct, and the latter to the subclavian vein. Their course and distribution were still more fully investigated by Thomas Bartholin, Wharton, Swammerdam, and Blaes, the two last of whom recognised the existence of valves; while Antony Nuck of Leyden, by rectifying various errors of his predecessors, and adding several new and valuable observations, rendered this part of anatomy much more precise than formerly.

After this period anatomists began to study more accurately organs and textures already known, and to obtain more precise knowledge of the intimate structure and organization of the human body. Francis Glisson distinguished himself by a minute description of the liver, and a clearer account of the stomach and intestines than had yet been given. Thomas Wharton investigated the structure of the glands with particular care; and though rather prone to indulge in fanciful generalization, he developed some interesting views of these organs; while Charle-ton, who appears to have been a person of great genius, though addicted to hypothesis, made some good remarks on the communication of the arteries with the veins, the foe-ļ tai circulation, and the course of the lymphatics. But the circumstance which chiefly distinguished the history of anatomy at the beginning of the seventeenth century, was the appearance of Thomas Willis, who rendered himself eminent not only by the first good researches on the brain and nerves, but by many judicious observations on the structure of the lungs, the intestines, the blood-vessels, and the glands. His anatomy of the brain and , nerves is so minute and elaborate, and abounds so much in new information, that the reader is struck by the immense chasm between the vague and meagre notices of his predecessors, and the ample and correct descriptions of Willis. This excellent work, however, is not the i result of his own personal and unaided exertions; and the character of Willis derives additional lustre from the: candid avowal of his obligations to Wren and Millington, and, above all, to the diligent researches of his fellowanatomist Richard Lower.

Willis was the first who correctly numbered the nerves, and described their origins in the order in which they have been generally named till the recent improvements of Soemmering. His observation of the connection of the eighth pair with the slender nerve which issues from the beginning of the spinal chord is known to all. He remarked the parallel lines of the mesolobe, afterwards minutely described by Vicq d’Azyr. He seems to have recognised the communication of the convoluted and figurate surfaces of the brain, and that between the lateral cavities beneath the fornix. He designates the objects of the central surface— the anterior as the lentiform eminences, with the striated appearance of their internal substance—the posterior as the optic chambers or thalami; the four orbicular eminences, with the bridge, which he first named annular protuberance ; and the white pisiform bodies, since called mammillary eminences, behind the infundibulum. In the cerebellum he remarks the arborescent arrangement of the white and grey matter, and gives a good account of the internal carotids, and the communications which they make with the branches of the basilar artery. Wep-for had already demonstrated the peculiar curvature of the former vessels in the carotic canal, and refuted the fiction of the rete mirabile.

About the same time the researches of Malpighi tended greatly to improve the knowledge of minute structure. He gave the first distinct ideas on the organization of the lung, and the mode in which the bronchial tubes and vessels terminate in that organ. By the microscope he traced the transition of the arteries into the veins. He examined the omentum, and inquired into the manner in which fat and marrow are secreted. He endeavoured to unfold, by dissection and microscopic observation, the minute structure of the brain. He demonstrated the organization of the skin, and considered its constituents as the organ of touch. He studied the structure of bone, and rectified the errors of Gagliardi; he traced the formation and explained the structure of the teeth; and he finally carried his researches into the substance of the liver, the spleen, the kidneys, and the conglobate glands. In these difficult inquiries the observations of Malpighi are in general faithful, and his descriptions are accurate. He may be regarded as the founder of that part of anatomical science which treats of structure and organization; and, even in the present day, his writings are both interesting and instructive.

Nicoas Steno described with accuracy the lacrymal gland and passages, and re-discovered the parotid duct. Bellini studied the structure of the kidneys, and described the tongue and tonsils with some care; and Drelincourt laboured to investigate the changes effected on the uterus by impregnation, and to elucidate the formation of the foetus. The science might have derived still greater advantages from the genius of Regnier de Graaf, who investigated with accuracy the structure of the pancreas and of the organs of generation in both sexes, had he not been cut off at the early age of 32. Lastly, Wepfer, though more devoted to morbid anatomy, made, nevertheless, some just observations on the anatomical disposition of the cerebral vessels, the glandular structure of the liver, and the termination of the common duct in the duodenum.

The appearance of Frederic Ruysch, who was born in 1638, and became professor of anatomy at Amsterdam in 1665, gave a new impulse to anatomical research, and tended not only to give the science greater precision, but to extend its limits in every direction. The talents of Ruysch are said to have been developed by accident. To repel the audacious and calumnious aspersions with which De Bils attacked De le Boe and Van Horne, Ruysch published his tract on the valves of the lymphatics, which completely established his character as an anatomist of originality and research. This, however, is the smallest of his services to the science. The art of injecting, which had been originally attempted by Eustachi and Varoli, and was afterwards rudely practised by Glisson, Bellini, and Willis, was at length carried to greater perfection by De Graaf and Swammerdam, the former of whom injected the spermatic vessels with mercury and variously coloured liquors, while the latter, by employing melted wax with other ingredients, made the first approach to the refinements of modern anatomy. By improving this idea of using substances, which, though solid, may be rendered fluid at the period of injecting, Ruysch carried this art to the highest perfection.

By the application of this happy contrivance, he was enabled to obtain more correct views than his predecessors of the arrangement of minute vessels in the interior of organs, and to demonstrate peculiarities of organization which escaped the scrutiny of previous anatomists. Scarcely[7:2:700] a part of the human body eluded the penetration of his syringe; and his discoveries were proportionally great. His account of the valves of the lymphatics, of the vessels of the lungs, and their minute structure; his researches on the vascular structure of the skin, of the bones, and their epiphyses, and their mode of growth and union; his observations on the spleen, the glans penis, the clitoris, and the womb impregnated and unimpregnated, were sufficient to give him the reputation of a skilful and accurate anatomist. These, however, were but a limited part of his anatomical labours. He studied the minute structure of the brain; he demonstrated the organization of the choroid plexus; he described the state of the hair when affected with Polish plait; he proved the vascular structure of the teeth; he injected the dura mater, the pleura, the pericardium, and peritoneum; he unfolded the minute structure of the conglomerate glands; he investigated that of the synovial apparatus placed in the interior of the joints; and he discovered several curious particulars relating to the lacteals, the lymphatics, and the lymphatic glands. So assiduously, indeed, did Ruysch study by injection the tissue of the organs of the animal body, that it is less easy to say what he did than what he neglected. To him we are indebted for many of the facts of which anatomy at the present day consists. The success of his injections, however, though it enabled him to trace the most delicate terminations of vessels in the substance of organs, perhaps exercised an unfavourable bias in making him look for vessels exclusively in the minute structure of all the tissues.

Meanwhile, Meibomius re-discovered the palpebral glands, which were known to Casserius; Swammerdam studied the action of the lungs, described the structure of the human uterus, and made numerous valuable observations on the coeca and pancreatoid organs of fishes; and Kerckringius attempted to explain the process of ossification, and determine its different stages. John Conrad Brunner, in the course of experiments on the pancreas, discovered the muciparous glands of the duodenum,—a fact to which Conrad Peyer gave a more generalized character by his description of the muciparous glands of the intestinal canal at large.' Leonard Tassin, distinguished for original observation, rendered the anatomical history of the brain more accurate than heretofore, and gave particular accounts of the intestinal tube, the pancreatic duct, and the hepatic ligaments. About the same time much light was thrown on the intimate constitution of several of the tissues, and on the minute communications of the arterial and venous tubes by the microscopical observations of Lecuwenhoeck.

That France might not be without participation in the glory of advancing the progress of anatomical knowledge, the names of Duverney and Vieussens are commemorated with distinction. The former, born in 1648, and first introduced into public life in 1676 in the Royal Academy of Sciences, decorated with the honorary title of professor of anatomy to the Dauphin, and appointed in 1679 professor at the Jardin Royal, distinguished himself by the first accurate account of the organ of hearing, and by his dissections of several animals at the academy, supplied valuable materials for the anatomical details of the natural history of animals published by that learned body. He appears to have been the first who demonstrated the fact, that the cerebral sinuses open into the jugular veins, and to have been aware that the former receive the veins of the brain, and are the venous receptacles of the organ. He understood the cerebral cavities, and their mode of communication; distinguishes the posterior pillars of the vault from the pedes hippocampi ; recognises the two plates of the septum lucidum ; and, what is still more remarkable, he first indicates distinctly the crossing or plaiting of the cerebral chords in the linear furrow between the right and left pyramidal bodies,—a fact afterwards verified by the researches of Mistichelli, Petit, and Santorini. He studied the ganglions attentively, and gives the first distinct account of the formation, connections, and distribution of the intercostal nerve. It is interesting to remark, that his statement that the veins or sinuses of the spinal chord terminate in the vena azygos has been verified by the recent researches of Dupuytren and Breschet, which show that the vertebral veins communicate by means of the intercostal and superior lumbar veins with the azygos and demi-azygos. His account of the structure of bones, and of the progress of ossification, is valuable. He recognised the vascular structure of the spleen; and he gives a correct account of the excretory ducts of the prostate gland, the verumontanurn, and the anteprostates.

One of the circumstances which the history of this period of anatomical science shows tended considerably to its improvement, is the attention with which Comparative Anatomy was beginning to be cultivated. In ancient times, and at the revival of letters, the dissection of the lower animals was substituted for that of the human body; and the descriptions of the organs of the latter were too often derived from the former. The obloquy and contempt in which this abuse involved the study of animal anatomy made it be neglected, or pursued with indifference, for more than two centuries, during which anatomists confined their descriptions, at least very much, to the parts of the human body. At this period, however, the prejudice against Comparative Anatomy began to subside; and animal dissection, though not substituted for that of the human body, was employed, as it ought always to have been, to illustrate obscurities, to determine doubts, and to explain difficulties, and, in short, to enlarge and rectify the knowledge of the structure of animal bodies generally.

For this revolution in its favour, Comparative Anatomy was in a great measure indebted to the learned societies which were established about this time in the different countries of Europe. Among these the Royal Society of London, embodied by charter by Charles II. in 1660, and the Academy of Sciences of Paris, founded in 1665 by Colbert, are undoubtedly entitled to the first rank. Though later in establishment,the latter institution was distinguished by making the first great efforts in favour of Comparative Anatomy; and Perrault, Pecquet, Duverney, and Mery, by the dissections of rare animals obtained from the royal menagerie, speedily supplied valuable materials for the anatomical naturalist. In England, Nehemiah Grew, Edward Tyson, and Samuel Collins, cultivated the same department with diligence and success. The first has left an interesting account of the anatomical peculiarities of the intestinal canal in various animals; and the second, in the dissection of a porpoise, an opossum, and an ourang outang, adduces some valuable illustrations of the comparative differences between the structure of the human body and that of the lower animals. To the third belongs the merit of conceiving, and executing on an enlarged plan, a comprehensive system, embodying all the information then extant. With the aid of Tyson and his own researches, which were both extensive and accurate, he composed a system of anatomical knowledge, in which he not only delivers ample and accurate descriptions of the structure of the human body, and the various morbid changes to which the organs are liable, but illustrates the whole by accurate and interesting sketches of the peculiarities of the lower animals. The matter of this work [7:2:701]is so excellent, that it can only be ascribed to ignorance that it has received so little attention. Though regarded as a compilation, and though indeed much of the human anatomy is derived from Vesalius, it has the advantage of the works published on the Continental that time, that it embodies most of the valuable facts derived from Malpighi, Willis, and Vieussens. The Comparative Anatomy is almost all original, and acquired from personal research and dissection; and the pathological observations, though occasionally tinged with the spirit of the times, show the author to have been endowed with the powers of observation and judicious reflection in no ordinary degree.

About this time also we recognise the first attempts to study the minute atomic constitution of the tissues, by the combination of the microscope and the effects of chemical agents. Bone furnished the first instance in which this method was put in use; and though Gagliardi, who undertook the inquiry, had fallen into some mistakes which it required the observation of Malpighi to rectify, this did not deter Clopton Havers and Nesbitt, in England, and Courtial, Du Hamel, and Delasone, and afterwards Hérissant, in France, from resuming the same train of investigation. The mistakes into which these anatomists fell belong to the imperfect method of inquiry. The facts which they ascertained have been verified by recent experiment, and constitute no unessential part of our knowledge of the structure of bone.

Ten years after the publication of the work of Collins, Henry Ridley, another English anatomist, distinguished himself by a monograph on the brain, which, though not free from errors, contains nevertheless some valuable ob- ‘ servations. Ridley is the first who distinguishes by name the restiform processes, or the posterior pyramidal eminences. He recognised the figure of the four eminences in the human subject; he remarked the mammillary bodies; and he discovered the sinus which passes under his name.

Raymond Vieussens, by the publication of his great work on neurography in 1684, threw new light on the configuration and structure of the brain, the spinal chord, and the nerves; and gave a description of the arrangement and distribution of the latter more precise than heretofore. Of the formation and connections of the sympathetic nerve especially he gave views which have 1 been generally adopted by subsequent anatomists. His new arrangement of the vessels, published in 1705, contains several curious and some hypothetical opinions. His observations on the structure of the heart, published in 1706, and enlarged in 1715, exhibit the first correct views of the intimate structure of an organ, which afterwards was most fully developed by the labours of Lancisi and Senac. His treatise on the ear is not superior to that of Duverney.

To the same period belong the rival publications of Godfrey Bidloo and William Cowper, the last of whom, however, stained a reputation otherwise good, by publishing as his own the engravings of the former. Cowper further distinguished himself by a minute account of the urethral glands, already known to Columbus and Mery; a good description of the intestinal glands, discovered by Brunner and Peyer; and by demonstrating the communication of the arteries and veins of the mesentery.

The anatomical genius of Italy, which had slumbered since the death of Malpighi, was destined once more to revive in Lancisi, Valsalva, and his illustrious , pupils Santorini and Morgagni. Valsalva especially distinguished himself by his description of the structure of the ear, which, in possessing still greater precision and minuteness than that of Duverney, is valuable in setting the example of rendering anatomy altogether a science of description.

Santorini, who was professor at Venice, was no unworthy friend of Valsalva and Morgagni. His anatomical observations, which relate to the muscles of the face, the brain, and several of the nerves, the ducts of the lacrymal gland, the nose and its cavities, the larynx, the viscera of the chest and belly, and the organs of generation in the two sexes, furnish beautiful models of essays distinguished for perspicuity, precision, and novelty, above any thing which had then appeared. These observations, indeed, which bear the impress of accurate observation and clear conception, may be safely compared with any anatomical writings which have appeared since. Those on the brain are particularly interesting. Morgagni, though chiefly known as a pathological anatomist, did not neglect the healthy structure. His Adversaria, which appeared between 1706 and 1719, and his Epistles, published in 1728, contain a series of observations to rectify the mistakes of previous anatomists, and to determine the characters of the healthy structure of many parts of the human body. Many parts he describes anew, and indicates facts not previously observed. All his remarks show how well he knew what true anatomical description ought to be. In this respect, indeed, the three anatomists now mentioned may be said to have anticipated their contemporaries nearly a century; for, while other authors were satisfied with giving loose and inaccurate or meagre notices of parts, with much fanciful supposition, Valsalva, Santorini, and Morgagni, laboured to determine with precision the anatomical characters of the parts which they describe.

The same character is due to Winslow, a native of Denmark, but, as pupil and successor of Duverney, as well as a convert to Catholicism, naturalized in France, and finally professor of anatomy at the Royal Garden. His exposition of the structure of the human body is distinguished for being not only the first treatise of descriptive anatomy, divested of physiological details and hypothetical explanations foreign to the subject, but for being a close description derived from actual objects, without reference to the writings of previous anatomists. About the same time Cheselden in London, the first Monro in Edinburgh, and Albinus in Leyden, contributed by their several treatises to render anatomy still more precise as a descriptive science. The Osteographia of the former was of much use in directing attention to the study of the skeleton, and the morbid changes to which it is liable. This work, however, magnificent as it was, was excelled by that of Albinus, who, in 1747, published engravings descriptive of the bones and muscles, which, perhaps, will never be surpassed either in accuracy of outline or beauty of execution. The several labours of this author, indeed, constitute an important era in the history of the science. He was the first who classified and exhibited the muscles in a proper arrangement, and applied to them a nomenclature which is still retained by the consent of the best anatomists. He gives a luminous account of the arteries and veins of the intestines, represents with singular fidelity and beauty the bones of the foetus, inquires into the structure of the skin, and the cause of its colour in different races; represents the changes incident to the womb in different periods of pregnancy, and describes the relations of the thoracic duct and the vena azygos with the contiguous parts. Besides these large and magnificent works, illustrated by the most beautiful engravings, six books of Academical Annotations were the fruits of his long and assiduous cultivation of anatomy. These contain valuable remarks on the sound structure and morbid deviations of numerous parts of the human body.

To render the knowledge of the skeleton more complete, Duhamel and Delasone studied the minute structure [7:2:702]of bone, and the process of ossification; William Hunter and Herissant investigated the texture of the cartilages; and Weitbrecht gave a copious and minute account of the ligaments. Μ. Lieutaud also, who had already laboured to rectify many errors in anatomy, described with much accuracy the structure and relations of the heart and its cavities, and rendered the anatomy of the bladder very precise, by describing the triangular space and the mammillary eminence at its neck.

Albinus found a worthy successor in his pupil Albert Von Haller, who, with a mind imbued with every department of literature and science, directed his chief attention, nevertheless, to the cultivation of anatomical and physiological knowledge. Having undertaken at an early age (21) to illustrate, with commentaries, the physiological prelections of his preceptor Boerhaave, he devoted himself assiduously to the perusal of every work which could tend to facilitate his purpose; and as he found numerous erroneous or imperfect statements, and many deficiencies to supply, he undertook an extensive course of dissection of human and animal bodies, to obtain the requisite information. For 17 years, during which he was professor at Goettingen, he dissected 400 bodies,^[9. “Pene quadringentis mea manu dissectis hominum cadavcribus.” (Praefatio ad tom. vi. Elementorum Physiologiae.) ] and inspected their organs with the utmost care. The result of these assiduous labours appeared at intervals in the form of dissertations by himself, or under the name of some one of his pupils, finally published in a collected shape, between 1746 and 1751 ( Disputationes Anatomicae Selectiores) ; and in eight numbers of most accurate and beautiful engravings, representing the most important parts of the human body, e. g. the diaphragm, the uterus, ovaries and vagina, the arteries of the different regions and organs, with learned and critical explanatory observations. Some years after, when he had retired from his academical duties at Goettingen, he published, between 1757 and 1765, the large and elaborate work which, with singular modesty, he styled Elements of Physiology. This work, though professedly devoted to the latter science, rendered nevertheless the most essential services to the former. Haller, drawing an accurate line of distinction between the two, gave the most clear, precise, and complete descriptions of the situation, position, figure, component parts, and minute structure of the different organs and their appendages. The results of previous and coeval inquiry, obtained by extensive reading, he sedulously verified by personal observation; and though he never rejected facts stated on credible authorities, he in all cases laboured to ascertain their real value by experiment. The anatomical descriptions are on this account not only the most valuable part of his work, but the most valuable that had then or for a long time after appeared; and it is perhaps a sufficient proof of their intrinsic merit, that they are still resorted to by the anatomist as the most faithful guide to many of his researches. It is painful, nevertheless, to think, that the very form in which this work is composed, with copious and scrupulous reference to authorities, made it be regarded as a compilation only; and that the author was compelled to show, by a list of his personal researches, that the most learned work ever given to the physiologist, was also the most abundant in original information.^[10. Ibid. ]

With the researches of Haller, it is proper to notice those of his contemporary, John Frederick Meckel, and his pupil John Godfrey Zinn. The former, who was professor of anatomy at Berlin, described with unrivalled accuracy the Gasserian ganglion, the first pair of nerves and its distribution, and that of the facial nerves generally, and discovered the spheno-palatine ganglion. He' made some original and judicious observations on the tissue of the skin and the mucous net; and above all, he recognised the connection of the lymphatic vessels with the veins,—a doctrine which, though neglected, has been lately revived by Fohmann and Lippi. He also collected several valuable observations on the morbid states of the heart and brain. At the same time Zinn, who was professor of medicine at Goettingen, published on the eye a classical treatise, which demonstrated at once the defects of previous inquiries, and how much it was possible to elucidate, by accurate research and precise description, the structure of one of the most important organs of the human frame. As a general proof of the extraordinary merit of this work, it is sufficient to say, that in critical learning and descriptive accuracy it has not been equalled, and probably will never be surpassed. It was re-published after his death by Wrisberg.

General anatomy, and the study of the atomic constitution of the tissues which had originally been commenced by Lecuwenhoeck, Malpighi, and Ruysch, began at this period to attract more general attention. De Bergen had already demonstrated the general distribution of cellular membrane, and shown that it not only incloses every part of the animal frame, but forms the basis of every organ,—a doctrine which was adopted, and still more fully expanded, by his friend Haller, in opposition to what was asserted by Albinus,^[11. Αnnot. Acad. lib. iii. p. 2. ] who maintains that each part has a proper tissue. William Hunter at the same time gave a clear and ingenious statement of the difference between cellular membrane and adipose tissue, in which he maintained the general distribution of the former, and represented it as forming the serous membranes, and regulating their physiological and pathological properties,— doctrines which were afterwards confirmed by his brother John Hunter. A few years after, the department of general anatomy first assumed a substantial form, in the systematic view of the membranes and their mutual connections traced by Andrew Bonn of Amsterdam. In his inaugural dissertation De Continuationibus Membranarum, published at Leyden in 1763, this author, after some preliminary observations on membranes in general and their structure, and an exposition of that of the skin, traces its transition into the mucous membranes and their several divisions. He then explains the distribution of the cellular membrane and the aponeurotic expansions, and the periosteum and perichondrium, by either of which, he shows, every bone of the skeleton is invested and connected. He finally gives a very distinct view of the arrangement of the internal membranes of cavities, those named serous and fibro-serous, and the manner of their distribution over the contained organs. This essay, which is a happy example of generalization, is remarkable for the interesting general views of the structure of the animal body which it exhibits; and to Bonn belongs the merit of sketching the first outlines of that system which it was reserved for the genius of Bichat to complete and embellish. Lastly, Bordeu, in an elaborate essay on the mucous tissue, or cellular organ, as he' terms it, brought forward some interesting views of the constitution, nature, and extent of the cellular membrane.

Though anatomy was hitherto cultivated with much success as illustrating the natural history and morbid states of the human body, yet little had been done for the elucidation of local diseases, and the surgical means by [7:2:703]which they may be successfully treated. The idea of applying anatomical knowledge directly to this purpose appears to have originated with Bernardin Genga, a Roman surgeon, who published in 1672, at Rome, a work entitled Surgical Anatomy, or the Anatomical History of the Bones and Muscles of the Human Body, with the description of the Blood-vessels. This work, which reached a second edition in 1687, is highly creditable to the author, who appears to have studied intimately the mutual relations of different parts. It is not improbable that the example of Genga led Palfyn, a surgeon at Ghent, to undertake a similar task about 30 years after. For this, however, he was by no means well qualified; and the work of Palfyn, though bearing the name of Surgical Anatomy, is a miserable compilation, meagre in details, inaccurate in description, and altogether unworthy of the honour of being republished, as it afterwards was, by Antony Petit.

While these two authors, however, were usefully employed in showing what was wanted for the surgeon, others were occupied in the collection of new and more accurate facts. Albinus, indeed, ever assiduous, had, in his account of the operations of Rau, given some good sketches of the relative anatomy of the bladder and urethra; and Cheselden had already, in his mode of cutting into the urinary bladder, shown the necessity of exact knowledge of the relations of contiguous parts. The first decided application, however, of this species of anatomical research it was reserved for a Dutch anatomist of the 18th century to make. Peter Camper, professor of Anatomy at Amsterdam, published in 1760 and 1762 his anatomicopathological demonstrations of the parts of the human arm and pelvis, of the diseases incident to them, and the mode of relieving them by operation. These observations are of the utmost value. The situation of the blood-vessels, nerves, and important muscles, is explained with the greatest clearness; and though the engravings are rather bold and accurate than elegant, they constitute a work indispensable to the anatomical reader. His remarks on the lateral operation of lithotomy, which contain all that was then known on the subject, are exceedingly interesting and valuable to the surgeon. It appears further that he was the first who examined anatomically the mechanism of ruptures, his delineations of which were published in 1801 by Soemmering.

It had been originally observed by Riolan, Severinus, Rndbeck, Harvey, and De Graaf, that in the foetus the testicles are situate in the abdomen; but this observation, so pregnant with important results, appears to have been overlooked, nay doubted, till verified by Haller, who showed that their removal from this region is connected with the formation of congenital hernia. The situation of the testicles previous to birth, their gradual descent into the scrotum, and the mode in which a portion of intestine may slip down with them, was still more fully investigated by William Hunter, by Camper, and finally by John Hunter; and the peculiarities of the inguinal canal, and the manner in which its persistence after birth, or its re-opening, may occasion hernial protrusions, have been well explained by Sandifort, Scarpa, Sir Astley Cooper, Allan Burns, and Lawrence, and more recently by Hesselbach and Langenbeck.

The attention of anatomists was now directed to the elucidation of the most obscure and least explored parts of the human frame—the lymphatic vessels and the nerves. Although, since the first discovery of the former by Asellius, Rudbeck, and Pecquet, much had been done, especially by Ruysch, Nuck, Meckel, and Haller, many points, notwithstanding, relating to their origin, and distribution in particular organs, and in the several classes of animals, were imperfectly ascertained or x entirely unknown. William Hunter investigated their arrangement, and proposed the doctrine that they are absorbents; and John Hunter, who undertook to demonstrate the truth of this hypothesis by experiment, discovered, in 1758, lymphatics in birds in the neck. As this doctrine required the existence of this order of vessels, not only in quadrupeds and birds, but in reptiles and fishes, the inquiry attracted attention among the pupils of Hunter; and William Hewson at length communicated, in December 1768, to the Royal Society of London, an account of the lacteals and lymphatics in birds, fishes, and reptiles, as he had discovered and demonstrated them. The subject appears about the same time to have been investigated by the second Monro, who indeed claimed the merit of discovering these vessels in the classes of animals now mentioned But whatever researches this anatomist may have instituted, Hewson, by communicating his observations to the Royal Society, must be allowed to possess the strongest as well as the clearest claim to discovery. The same author, in 1774, gave the first complete account of the anatomical peculiarities of the lymphatic system in man and other animals, and thereby supplied an important gap in this department. Hewson is the first who distinguishes the lymphatics into two orders, the superficial and the deep, both in the extremities and in the internal organs. He also studied the structure of the intestinal villi, in which he verified the observations of Lieberkuhn; and in inquiring into the minute structure of the glands, he adopted the views of Ruysch. He finally applied his anatomical discoveries to explain many of the physiological and pathological phenomena of the animal body. Ten years after, John Sheldon, another pupil of Hunter, gave a second history and description of the lymphatics, which, though divested of the charm of novelty, contains many interesting anatomical facts. He also examined the structure of the villi. And, lastly, Cruikshank, in 1786, published a very valuable history of the anatomy of the lymphatic system, in which he maintains the accuracy of the Hunterian doctrine, that the lymphatics are the only absorbents; gave a more minute account than heretofore of these vessels, of their coats and valves; and supplied the defect left by Hewson, by explaining the structure of the lymphatic glands. He also injected the villi, and examined them microscopically, verifying most of the observations of Lieberkuhn. The origin of the lymphatics he maintains rather by inference than direct demonstration. To these three works, though in other respects very excellent, it is a considerable objection that the anatomical descriptions are much mixed with hypothetical speculation and reasonings on properties, and that the facts are by no means always distinguished from mere matters of opinion. At the same time Haase published an account of the lymphatics of the skin and intestines, and the plexiform nets of the pelvis.

To complete this sketch of the history of the anatomy of the lymphatic system, it may be added that Maseagni, who had been engaged from the year 1777 to 1781 in the same train of investigation, first demonstrated to his pupils several curious facts relating to the anatomy of the lymphatic system. When at Florence in 1782, he made several preparations, at the request of Peter Leopold, grand duke of Tuscany; and when the Royal Academy of Sciences at Paris announced the anatomy of this system for their prize essay appointed for March 1784, Maseagni resolved on communicating to the public the results of his researches—the first part of his commentary, with four engravings. Anxiety, however, to complete his preparations detained him at Florence till the close of 1785; and from these causes his work did [7:2:704]not appear till 1787. These delays, however, unfavourable as they were to his claims of priority to Sheldon and Cruikshank, were on the whole advantageous to the perfection of his work, which is not only the most magnificent, but also the most complete, that ever was published on the lymphatics. In his account of the vessels and their valves, he confirms some of Hewson’s observations, and rectifies others. Their origins he proves by inference much in the same manner as Cruikshank; but he anticipates this author in the account of the glands, and he gives the most minute description of the superficial and deep lymphatics, both in the members and in the internal organs.

General accounts of the nerves had been given with various degrees of accuracy by Willis, Vieussens, W inslow, and the first Monro; and the subject had been much rectified and improved by the indefatigable Haller. The first example of minute descriptive neurography was given in 1748 by J. F. Meckel, whose account of the fifth pair, and their connection with the intercostal, and of the nerves of the face, will long remain a lasting proof of accuracy and research. The same subject was investigated in 1765 by Hirsch, and in 1777 by Wrisberg. In 1766 Metzger examined the origin, distribution, and termination of the first pair,—a point which was afterwards very minutely treated by Scarpa in his anatomical disquisitions published in 1780; and the internal nerves of the nostrils were examined in 1791 by Haase. The optic nerve, which had been studied originally by Varoli, and afterwards by Mery, Duverney, Henkel, Moeller, Hein, and Kaldschmid, was examined with extreme accuracy, with the other nerves of the organ of vision, by Zinn, in his elaborate treatise. The phrenic nerves, and the oesophageal branches of the eighth pair, were studied by Haase; the phrenic, the abdominal, and the pharyngeal nerves, by Wrisberg; those of the heart most minutely by Andersch; and the origins, formation, and distribution of the intercostal nerve, by Iwanoff, Ludwig, and Girardi. The labours of these anatomists, however, were eclipsed by the splendid works of Walter on the nerves of the chest and belly; and those of Scarpa on the distribution of the 8th pair, and splanchnic nerves in general. In minuteness of description, and in beauty of engraving, these works have not yet been equalled, and will never perhaps be surpassed. About the same time Scarpa, so distinguished in every branch of anatomical research, investigated the minute structure of the ganglions and plexuses.

The brain was also studied with great attention by Ma-lacarne, Vicq d’Azyr, and Soemmering; more recently Reil examined the minute structure of the organ and its component parts with unrivalled research and accuracy; and Rolando studied the structure of the cerebellum.

Lastly, the anatomy of the gravid uterus, which had been originally studied by Albinus, Roederer, and Smel-lie, was again illustrated most completely by William Hunter, whose engravings will remain a lasting memorial of scientific zeal and sculptorial talent.

The perfection which anatomical science has attained, has been evinced during the last 30 years in the improved character of the systems published by anatomists. The first who gave a good modern system was Sabatier; but his work was speedily eclipsed by the superior merits of the treatises of Soemmering, Bichat, and Portal. To the first belongs the character of being at once the most learned and critical, and at the same time the most precise, yet published. The General Anatomy of Bichat is a monument of his philosophical genius, which will last as long as the structure and functions of the human body are objects of interest. His Descriptive Anatomy is distinguished by clear and natural arrangement, precise and accurate description, and the general ingenuity with which the subject is treated. The physiological observations' are in general correct, often novel, and always highly interesting. It is unfortunate, however, that the ingenious author was cut off prematurely during the preparation of the third volume. It must nevertheless be acknowledged, that if the two last ones betray the want of the genius of Bichat, they are pervaded with the general spirit by which the others are impressed, and are highly creditable to the learning, the judgment, and the diligence of MM. Roux and Buisson. The system of Portal is a valuable and correct digest of anatomical and pathological knowledge, which, in exact literary information, is worthy of the author of the History of Anatomy and Surgery, and, in accuracy of descriptive details, shows that Μ. Portal trusts not to the labours of his predecessors only. Since the appearance of these standard works, Meckel published a Manual, which combines the philosophical generalizations of Bichat with the precise description and pathological knowledge of Portal. This work has been recently translated into French. Lastly, Cloquet formed, on the model of the Descriptive Anatomy of Bichat, a system in which he avails himself of the literature and precision of Soemmering, and the details of Portal. The system of Gordon is imperfect, its completion being interrupted by the death of the author; but, so far as it goes, it gives a correct summary of General Anatomy, and some accurate descriptive details of the heart and brain. The work of Dr Monro is entitled to mention in this place, as an elementary treatise, containing, with anatomical description, a good deal of physiological and pathological matter. These, however, must be considered foreign to the subject.

Of treatises on particular departments, those of Blumenbach on the bones, Innes and Sandifort on the muscles, the several anatomical writings and engravings of Charles Bell on the arteries, the nerves, and the brain, Barclay on the arteries, Tiedemann on the nerves of the uterus, and the same author’s engraved delineations of the arteries, and Harrison’s excellent work on the arteries, deserve notice. The minute structure of bone which had been examined by Scarpa, was again studied by that indefatigable inquirer, and in this country by Howship. The structure of the lungs was investigated by Reisseissen, by Magendie, and Sir E. Home. On the anatomy of the nervous system numerous treatises have lately appeared. Joseph and Charles Wenzel investigated the minute structure of the brain in man and the lower animals; Tiedemann traced the development of the organ in the foetus, and rectified many errors on its formation and minute structure; Sir Everard Home and Μ. Bauer investigated its atomic constitution by the microscope; Lobstein investigated the structure and distribution of the great sympathetic nerve; Bellangeri published an accurate description of the spinal chord and its nerves; and, lastly, Charles Bell, in his great work on the nervous system, developes and establishes the truth of the ancient theory of the separate nature of the nerves of motion and those of sensation. Comparative Anatomy has been diligently cultivated by Daubenton, Pallas, Haller, John Hunter, and the second Monro, and more recently by Cuvier, Dumeril, Home, Tiedemann, and Meckel.

In the foregoing account we have been anxious to trace merely a general sketch of the progressive advancement of anatomical discovery, from the first cultivation of the art to the present time. To mention every circumstance is impracticable, and would have extended this outline much beyond its legitimate limits. Though no name of genuine [7:2:705]importance, however, has been omitted, every one not directly connected with strict anatomy has been excluded. At the same time it has been found impossible to specify every individual who has contributed at different periods to the improvement of the science; and these we shall in general notice occasionally as we require to speak of them in the account of particular parts. For more minute and detailed information, we refer in general to the elaborate History of Anatomy and Surgery by Portal, the Bibliotheca Anatomica of Haller, and the critical and learned history of Lauth. It is unfortunate that the latter work is not completed· But by combining its perusal with that of the works already mentioned, and several of the chapters of Sprengel’s History of Medicine, the anatomical inquirer will form very just ideas of the literary history of his science.^[12. Histoire de l' Anatomie et de la Chirurgie, <∣∙c. par Μ. Portal, Lecteur au Roi, &c. Paris, 1770-1773, 6 vols. Bibliotheca Anatomica, gua Scripta ad Anatomen et Physiologiam facientia a rerum initiis recensentur. Auctore Alberto von Haller Domino a Goumaens, &c. Tiguri, 1774-1777, 2 vols. 4to. Histoire de l’Anatomie, par Thomas Lauth, D. Μ. &c. &c. Strasbourg, 1815. Versuch einer pragmatischen Geschichte der Arzncikunde von Kurt Sprengel. Halle, 1792-1803. ]

HUMAN ANATOMY.

All animal bodies agree in the possession of certain general characters, by which they are distinguished equally from inorganic bodies and from vegetables.

Besides the round shape by which organic bodies are distinguished, most animals are, externally at least, symmetrical, or present on each side of the mesial plane, lateral halves mutually alike. The substances of which they consist are not entirely solid, but are soft, compressible, distensible, and elastic, and contain a proportion of liquid matter, which is generally in the ratio of majority to that of the solid. These substances are enveloped in a thready or filamentous matter, named areolar or cellular, from the interstitial spaces which result from the intersection of its filaments; and the whole is inclosed in a general covering, which in several classes is soft, membranous, and elastic, but in others is hard, crustaceous, and even homy. The body is perforated by an internal cavity for the reception of food; and this cavity is lined by a membranous covering, which is continuous with that by which the exterior is involved. In several classes of animals there are tubular canals, distributed in an arborescent form, for conveying, in definite directions, the nutritious matter to all parts of the frame. These are named bloodvessels, or organs of circulation. One modification of these, arranged in such manner that this matter is subjected to the influence of the atmospheric air, forms lungs, gills, or organs of respiration ; and another, in which part of it is separated from the whole, constitutes secreting organs or glands. The genital or reproductive organs consist of a cavity, from which the germs or ova are detached. For the purpose of motion, animals further possess organs generally of a fibrous structure, and which have the remarkable property of undergoing contraction on the application of a stimulus or irritating agent. These organs are denominated muscles (lacerti, tori) ; and their contractile property is termed irritability or contractility. For receiving the impression of external objects, they are provided with one or more organs of sensation, of structure more or less complex. And in almost all animal bodies, except the very lowest, there are found soft, gray, or whitish cords, inelastic, but marked in their course by fusiform, spheroidal, or irregular-shaped swellings, and connected at their further extremity with the muscles, with the organs of sensation, or with the exterior or interior coverings. It is remarkable that the purpose of these cords, which are named nerves, is not exactly known. They neither communicate mobility to the muscles, nor sensibility to the organs of sensation; but they render the actions of the former steady, regular, and voluntary; and the impressions received by the latter they certainly serve to convey to the centre of the nervous system.

The faculty ascribed to the nerves is named nervous action, nervous energy, nervous power, nervous inβuence, or simply innervation.

In chemical composition, animal bodies consist of gelatine, albumen, fibrin, fat or oleaginous matter, a modification of mucus, and various saline substances. Subjected to combustion, or spontaneous decomposition, while vegetable substances furnish water, çarbonic acid, and carburetted hydrogen, animal matters furnish also ammonia,—a circumstance which shows that they contain azote. They furnish also sulphuretted hydrogen, apparently from the decomposition of albuminous matters.

The fluids of animal bodies (liquores, latices, humores) are contained in tubular canals or vessels. If these fluids move through the vessels, they are denominated generally blood, whatever be their colour. All the fluids consist either of this, or of some modification separated from it by means of glandular action; and of the fluids so separated, some are destined for purposes within the economy, and are therefore secretions proper; others are intended to be eliminated immediately, and may therefore be regarded as excretions. Though it is impossible to estimate accurately the proportion of the fluids, some idea of it may be formed by the fact, that an animal body may be reduced by desiccation to ⅜ or ∙⅛ even of its previous weight. The proportion may be stated, in general terms, to vary from 9 or 6 of fluid, to 1 of solid matter.

The various forms of animal bodies may be referred to general divisions or classes, according to certain peculiarities in configuration and structure. These divisions are, the Vertebrata, Mollusea, Articulata, and Radiata.

In the first class the central portion of the nervous system, consisting of the brain and spinal chord, is inclosed in a case of hard matter, containing much calcareous earth, and denominated bone. While one portion of this forms, by the union of its pieces, a cavity named the scull or cranium, the other is composed of separate pieces, which by their union constitute at once a continuous canal and a sort of internal pillar or column for attaching and supporting the soft parts. These pieces are named vertebrae (δ-zovδυλοι) ; and their presence is so uniform, that they constitute the character of the class, which are therefore named Vertebrated Animals; (Animalia Vertebris praedita, sive Vertebrata).

The presence of vertebrae is accompanied with other peculiarities of structure. Thus the vertebrated animals have red blood and a muscular heart; a system of tubes for conveying blood from this to the different organs,—the distributory, or arteries; another system for returning it,—the regredient, or veins; and a particular system of [7:2:706]vessels for exposing the latter blood to the influence of the atmosphere. They have further a mouth with two horizontal jaws; distinct organs of vision, hearing, smell, and taste, lodged in the cavities of the face; never more than four members; separate sexual organs; and considerable similarity in the arrangement of the central masses and the ramified chords of the nervous system. In all the vertebrated animals the blood which serves for the secretion of bile is the venous, which has circulated in the intestines, and which is afterwards made to undergo a ramifying distribution in the portal vein. In all the vertebrated animals also a peculiar secretion is formed from the arterial blood by two large glands, denominated kidneys.

In the second general division, which are destitute of those firm pieces named bones, the central portion of the nervous system, instead of being inclosed in portions of the skeleton, is placed on the oesophagus, and, with the other internal organs, is inclosed in a general soft envelope, contractile, corresponding to the skin, to which the muscles are attached, and in which stony patches named shells are occasionally formed. Of the four proper organs of sensation, those only of taste and sight are observed; and the last are often wanting. One family only are provided with organs of hearing. There is always a complete system of circulation, and organs for respiration. Those of digestion and secretion are almost as complicated as in the vertebrated animals. The division of the animal world thus distinguished have been named Molluscous Animals ; (Animalia Mollusea).

In the third general division, the nervous system consists of two chords extending longitudinally along the belly, and swelling at intervals into knots or ganglions. The first of these, placed on the oesophagus, and distinguished as the brain, is scarcely larger than the others. The covering of the trunk is divided by transverse folds into a number of rings, the integuments of which may be hard or soft, but to the interior of which muscles are in all cases attached. The sides of the trunk, though often provided with, are nevertheless often without, articulated members. The annular appearance of the trunk has given these animals the character of Articulated; (Animalia Articulata). They have been occasionally named Annulosa.

This class of animal bodies is remarkable for presenting the first transition from circulation in close tubes or vessels, to nutrition by imbibition, and the corresponding transition from respiration in circumscribed organs to that which takes place in air-tubes distributed through the whole body. The only distinct organs of sensation are those of taste and sight.; and a single family have organs of hearing. The jaws, when present, are lateral.

In these three divisions of animals the organs of motion and sensation are arranged symmetrically on both sides of an axis or imaginary line. In a fourth class they are distributed circularly round a centre. In these, which in homogeneous structure approach the nature of plants, neither distinct nervous system nor proper organs of sensation are observed. Scarcely do we recognise traces of circulation. The organs for respiration are almost always at the surface of the body. Most of them have for intestine a sac without vent; and some present only a homogeneous pulp, movable and sensible. To this class, which comprehends those beings denominated since the time of Aristotle zoophytes (ζωόφυτα), or animal plants, the name of Radiated Animals has been recently applied; (Animalia Radiata).

The vertebrated animals, however similar in general characters, present certain peculiarities by which they are naturally distinguished into classes. The first, and perhaps the most striking difference, is in the mode of birth, one large division being separated from the body of the female parent in a state of complete life, and therefore denominated viviparous; the other being detached in the form of an ovum or egg, which, though possessed of the elements of life, is not yet endowed with it, and requires for the full developement of that principle the assiduous care of the parent. This difference, however obvious, is more apparent than real. In viviparous birth the foetus or new animal remains attached to the inner surface of the womb by means of nutrient bl∞d-vessels, and is enveloped in membranes, which correspond very accurately to the coverings of the ova of oviparous animals. The rupture of these membranes at the moment of birth or detachment from the body of the parent is the only circumstance which constitutes a material difference between viviparous and oviparous generation. The viviparous animals, nevertheless, are further distinguished by nursing their offspring by means of teats or mamrnae, glands destined for separating from the mass of blood the oleo-albuminous fluid denominated milk.

A still more important source of distinction among the vertebrated animals is found in the disposition of the vascular organs destined for respiration. The blood, which proceeds from the heart by the distributing tubes or arteries to the different organs, thereby undergoes a certain change, in consequence of which it is no longer capable of answering the several purposes of nutrition, secretion, &c. which are necessary to the maintenance of the animal body in the healthy state. To fit it once more for these purposes, the blood, in whole or in part, is, by means of the veins, brought back to the heart, and thence conveyed by means of a system of arborescent tubes to the surface of an organ, where it is, through the interposition of a thin membrane, exposed more or less freely to the atmospheric air. When it is exposed directly to this fluid introduced into the body by means of a single tube divided into ramifying branches, the respiratory organ is denominated lungs. When the blood, on the other hand, is exposed to atmospheric air by means of water, which passes over a pectiniform organ, the latter is denominated gills. Respiration varies, therefore, according as the structure of the organ allows the whole or part of the blood to be exposed to air, and according as this exposure is direct or indirect.

Taken together, these circumstances may be viewed as the integrant or constituent elements of the quantity, extent, or degree of respiration, which conversely, indeed, depends on two circumstances,—the quantity of blood present in the respiratory organ at any given moment, and the relative quantity of oxygen in the respired fluid.

The organs of circulation may be double, so that the whole mass of blood which is brought by the veins from the remote parts must circulate in the respiratory organ before it is again distributed by the arteries ;—or they may be single, so that one portion only of the regredient blood is made to pass through the respiratory organ, while the residue is distributed by the arteries without undergoing this circulation. Of this mode of respiration an example is given by the class of animals denominated Reptiles; (Reptilia ; Animalia Repentia) ; in which the heart is so constructed that only part of the blood is conveyed to the lungs, and in which, consequently, the amount or degree of respiration, and the concomitant qualities, vary according to the proportion of this fluid which goes to the lungs at each pulsation.

In Fishes, on the other hand, though the circulation is two-fold, that is, distributory by means of arteries, and [7:2:707]regredient by means of veins, the respiratory organ is formed for respiration through the medium of Water, and the blood thus exposed to air receives the influence of that only which is mingled or held in solution by the water. Their extent of respiration is therefore supposed to be less than that of reptiles, by reason of the imperfect exposure to the operation of the air. Their respiration may be termed hydro-aerial.

In mammiferous animals, again, though the circulation is two-fold, or distributory and regredient, the respiration is single, or confined to the lungs only. Their extent of respiration is' therefore superior to that of the reptiles, by reason of the shape of their circulatory organs, and to that of fishes by reason of the nature of the element in which they live. Their respiration is aerial.

In another class of vertebrated animals, however, respiration assumes a form still more perfect and extensive, since not only is the circulation two-fold, and the respiration aerial, as in the mammalia, but their structure is such that the air of the trachea communicates with other cavities, especially those of the bones, and surrounds the branches of the aorta as completely as it does those of the pulmonary artery. The effect of this arrangement with regard to the ambient atmosphere is at once to render these animals specifically lighter, and enable them to support themselves in the air, and to restore and change the regredient or venous blood so completely, that when again distributed it may impart to the various organs the highest degree of energy of which they are susceptible.

From these characters a division of vertebrated animals may be formed in the following manner. 1sZ, Quadrupeds, in which the extent of respiration is moderate, and which are distinguished for walking or running, or other muscular exertion with strength; 2<rf, Birds, in which the extent of respiration is the greatest possible, and is connected with the levity of substance and energy of muscle requisite for flight; 3d, Reptiles, in which the small extent of respiration is connected with languor of motion and occasional seasons of torpor; and, 4∆4, Fishes, in which the still more limited form of the respiratory organ requires a fluid of nearly equal specific weight to their own bodies to enable them to move with facility. These characters are necessarily general; but they are so essential, that between them and the other circumstances of organization proper to each class, and especially those relating to motion and sensation, a necessary relation exists.

To the quadrupeds, mammiferous animals, or viviparous vertebrated animals, which form the first of these great classes, this place belongs, not only by the mode of generation and respiration, but by the more perfect form of the animal functions, and the higher degree of intelligence which their habits and actions indicate. They are less under the influence of that blind animal propensity denominated instinct, which, like the properties of inorganic matter, seems to operate regularly and uniformly, independent either of sensation or volition.

This class of animals is distinguished by great uniformity and regularity of structure and organization. In all of them the upper jaw forms part of the cranium; and upon this the lower jaw, consisting of two pieces only, articulated by a prominent condyle to the temporal bone, is made to move. The neck consists of seven, and, in one species only, of nine vertebrae; to the sternum are attached certain of the ribs, therefore named sterno-vertebral ; the thoracic extremity is supported by a flat bone named shoulderblade (scapula, ωμοπλάτη), not articulated, but simply suspended in the muscles, and in some species supported on the sternum by an intermediate bone, named collar-bone or clavicle (clavicula, ×λη ∣ ς) ; in all excepting the cetacea or whale-like animals, the first part of the pelvic extremity is fixed to the vertebral column, and forms a cincture or basin (pelvis), which in early life is divided into three pairs of bones, the os ilium, which is attached to the spine, the os pubis, which constitutes the anterior or abdominal part of the pelvis, and the os ischium, which constitutes the most remote lateral portions of the pelvis. At the point of junction of these three bones on each side is a spherical cavity, in which the articular head of the thigh-bone is lodged.

The scull, articulated by two prominent convex surfaces with the first vertebra, denominated atlas, may be represented as consisting of three annular portions, an anterior formed by the frontal and ethmoid bones, a middle by the parietal and sphenoid bones, and a posterior by the occipital bone; the temporal bones, which are common to the face and scull, being interposed between the sphenoid, the occipital, and the parietal bones.

The face is formed essentially by the superior and inferior maxillary bones. Between the former is the cavity of the nostrils above, separated by the azygos bone named vomer ; before are the intermaxillary bones, and behind are the two palate bones. The entrance of the nasal cavity is bounded above by the proper nasal bones; and to a groove in this cavity are attached the inferior turbinated bones, so as to cover partially the entrance into the maxillary sinus.

The brain consists of two similar hemispherical halves, united by a white mass, fibrous, especially in the transverse direction, named mesolobe, middle-band, or smooth body (δωμa τιλλos ∣ δις, corpus callosum). Each hemisphere contains an interior cavity, formed into definite-shaped masses, uniform and symmetrical. These cavities communicate with each other, and with a third situate on the mesial plane, and extending by a narrow canal to a fourth situate between the cerebellum and medulla oblongata. The proper matter of the cerebral and cerebellic hemispheres is united on the mesial plane in a mass named annular protuberance or pons Varolii, the lower surface of which is marked by transverse fibres, while the upper is moulded into four roundish eminences named nates and testes, or corpora quadrigemina.

In the eye, lodged in a cavity of the cranium named orbit, and provided with two eye-lids and the vestige of a third, the crystalline lens is fixed by the ciliary processes; and the sclerotic, though firm, is cellular. The ear consists of a cavity named tympanum, closed externally by a membrane, and containing four minute but articulated and movable bones; an oval cavity or vestibule, in the orifice of which, one of these bones, the stapes, is fixed, and which communicates with three semi-circular canals; and, lastly, a spiral and tapering cavity, termed cochlea, parted by a thin plate into two spiral canals, one of which communicates with the tympanum, the other with the vestibule. The tongue is fleshy, and is supported by a parabola-shaped bone, attached to the cranium by ligaments, and to the larynx by membranes.

The lungs, in number two, consisting of numerous tubular canals, proceeding from the windpipe, and terminating in an infinity of minute intersecting canals, named cells or vesicles, are inclosed without attachment, in a cavity formed by the ribs on each side, the diaphragm abdominally, and on the mesial plane by a membranous partition named mediastinum, and lined all over by a thin transparent membrane; (pleura). At the guttural extremity of the windpipe is placed a particular apparatus, formed of cartilages put in motion by muscles, and which serves at once to regulate the quantity of air admitted into the tube, and to form the voice. This is named the [7:2:708]larynx. A membranous fleshy production, suspended from the palate bones like a veil or valve, also moved at the will of the animal, establishes a direct communication between the larynx and the posterior nostrils.

The intestinal canal is suspended to a duplicature of the peritoneum, named mesentery, between the folds of which the blood-vessels, nerves, lymphatics, and lymphatic glands pertaining to the canal, are lodged. The peritoneum, after passing over the intestines, forms a similar duplicature, which in the manner of a prolongation hangs freely before them.

The urine, after secretion by the kidneys, is retained for a time shorter or longer in a distensible musculo-membranous bladder, and is expelled at various periods by a canal which opens, with few exceptions, in common with that of the organs of generation.

. The latter function is, in all the mammiferous animals, essentially viviparous. The ovum, consisting of the foetus and the enveloping membranes, immediately after conception is conveyed by appropriate tubes into the womb, to the inner surface of which it is attached by one or more plexiform clusters of vessels named placentoe, and which furnish the blood requisite to the nourishment of the new body. In the earliest periods of uterine life, however, the mammiferous animals present a bladder or vesicula (vitellar membrane), analogous to that which contains the yolk of the oviparous animals, and receiving also mesenteric vessels.

The peculiar mode in which viviparous animals nurse their offspring has been already noticed as that which distinguishes them particularly from the other three divisions of vertebrated animals.

Another character peculiar to this class, are the hairs with which their integuments are provided, and which, though analogous to the feathers or quills of birds,are nevertheless so characteristic, that they cannot be properly omitted in this enumeration. They are found in all mammiferous animals except the cetacea, in which marine residence is supposed to render them less necessary. Lastly, the blood of the mammalia is said to differ from that of oviparous animals in the shape of the coloured particles. In the former they are represented as lenticular, or of the shape of flat or oblate spheroids; in the latter they are ovoidal, or like oblong spheroids.

The mammiferous animals may be subdivided into subordinate groups or orders, according to certain natural characters in organization, which imply again peculiarities of habit and mode of life. These characters are derived from the organs of touch or prehension, on which depends their degree of ability or address; and from the organs of mastication, which always bear a certain relation to the nature of the food on which the individual animal subsists.

The delicacy of the organ of touch depends on the number and mobility of the toes, and on the extent to which their tips are enveloped in nail or hoof. The latter, enveloping entirely the part of the foot which touches the ground, impairs sensation, and renders the foot or paw incapable of prehension. When, on the contrary, a single plate of nail covers one of the surfaces of the tip of the toe, it not only leaves the other all its natural nicety of touch, but gives each toe that free and unembarrassed motion which enables the animal to seize and hold by the claws.

The nature of the aliment used by animals bears a relation to the teeth, with the form of which, again, the articulation of the jaws corresponds. To divide flesh, incisive teeth, like a saw, and jaws mutually opposed, like the blades of scissors, which simply open and shut, are requisite. In order to break grains or roots, teeth with a flat crown, ’ and jaws admitting of horizontal motion, are required. The crowns of these teeth must further be unequal or tuberculated, like the surface of a mill-stone, and their substance must be unequally firm, since certain parts are more exposed to attrition than others.

All hoofed animals are necessarily herbivorous, or have flat-crowned teeth, since their feet do not allow them to seize living prey. Unguiculated animals, again, are susceptible of greater variety in the shape of the teeth, and their aliment depends on the mobility and delicacy of their toes. One character of this description, which exercises great influence on their address, and multiplies their means of industry, is the faculty of opposing the great toe to the others, or the thumb to the fingers,— a circumstance which essentially constitutes what is termed the hand, and which is carried to its highest perfection in the case of man, in whom the pectoral extremity is entirely free and susceptible of every mode of prehension.

The several combinations now mentioned furnish characters for distinguishing the mammalia into the following orders.
[table]

Of these subdivisions, the first three orders are known by the common character of possessing all the three varieties of teeth, molar, canine, and incisive. They differ from each other in the possession of complete hands on the thoracic extremities, of imperfect hands on the four extremities, and in the want of thumb or opposable toe on the four extremities. The fourth order is peculiar in wanting canine teeth, and having incisors constructed for gnawing. In the fifth the toes are much constrained in motion, being sunk in large claws; and the incisors are wanting. Some genera want the canine teeth, and some are void of teeth entirely.

This distribution of unguiculated animals would be complete, and would form a regular series, were it not interrupted by a small lateral series from New Holland, the native soil of the Marsupial animals. Of these, it is the peculiar distinction, that while some of their genera correspond to the Carnivora, others to the RoDENTJA,and a third set to the Edentata, in the form of teeth and nature[7:2:709] of food, all of them agree in the common character of having a large sac or purse (marsupium) for retaining some time after birth their offspring, which are detached from the body of the parent in a state of imperfection, corresponding nearly to the foetus of other mammiferous animals shortly after conception. ∙

In the series of hoofed animals, which are less numerous, less irregularity is also observed. The order of Ruminant animals is well distinguished by cloven feet, the absence of incisors in the upper jaw, and the quadruple stomach, or that with four compartments. The other hoofed quadrupeds maybe unitedin one order, distinguished by the absence of the ruminating stomach, and a peculiar density of integuments, from which they are named Paciiydermata. The elephant alone constitutes a distinct family, and is allied, by the form and mechanism of the teeth, with the family of Rodentia. A third family of hoofed quadrupeds is distinguished by one apparent toe and one hoof in each foot; though beneath the skin, on each side of the metacarpus and metatarsus, are prominences corresponding to lateral toes. This small family (Solidipeda) includes the horse, ass, zebra, and quagga.

Lastly, the Cetaceous or whale-like animals form a family by themselves, so peculiar, that though viviparous and mammiferous, they might readily be regarded as belonging to the class of fishes. Their organization, however, immediately shows their proper place in the classification; and even the fact observed by the ancients, that, though pisciform, they have warm blood, demonstrates their title to the character of Mammalia.

Man, who, as the most perfect specimen of mammiferous animal with which we are acquainted, is placed at the head of this class, partakes of the general characters of structure and function belonging to the class, and possesses also certain peculiarities by which he is distinguished. The study of the facts of the former description belongs properly to Comparative or Animal Anatomy. That of the latter constitutes Human Anatomy proper. It is, however, expedient to waive this distinction, and trace the anatomical history of the human body, without supposing the reader already minutely acquainted with the structure of mammiferous animals in general. In the course of this description, however, it is requisite to recur frequently to the lower animals, and to derive from them information more or less direct, tending to illustrate the structure of the human subject.

The external appearance of the human frame it is superfluous to describe minutely. Naturalists distinguish man as a bimanous and biped animal, or as one possessing two complete hands, and supporting himself in the vertical position by the two pelvic extremities. These characters are neither arbitrary nor unessential. Both depend on invariable peculiarities of structure; and whatever attempts have been made by men, more distinguished for ingenious paradox than accurate observation, to show that man was naturally quadruped, are readily refuted by appealing to the anatomical configuration and disposition of the four members, and their relation to the trunk.

Another character of the human subject is the globular or rather spheroidal shape of the skull, and its large size in proportion to the rest of the frame, with the general tendency of the plane of the face to the vertical direction. In no other mammiferous animal does the head make so near an approach to the spheroidal shape; and in no other is the plane of the face so nearly vertical. In the other Mammalia, the skull is angular-oblong, and the face acquires a peculiar character, which is readily ascribed to the lower animals by the extreme projection of the mouth, or, in other words, by the length to which the two jaws are prolonged. Even in the monkey tribe, the similitude of which to the human face was remarked by the poet Ennius, this remarkable character is by no means lost; and the upper and lower jaws make a much more conspicuous projection than in the human skull.

The great characteristic of the human race, however, is articulate or oral speech, which, combined with the perfect developement of which the mental faculties are susceptible, constitutes a very wide distinction between man and the lower animals. The latter possess what may be termed laryngeal voice, or that which is formed in the larynx. To man is superadded the faculty of articulate speech by means of the lips, tongue, and teeth.

All the known individuals of the human species, though agreeing in the possession of the general characters now enumerated, and therefore to be regarded as unigenous, or of one general family, differ nevertheless by certain peculiarities in external characters, which have been supposed sufficient to justify the separation into individual races or breeds. Of these, three appear to be very distinct, the White or Caucasan, the Tawny or Mongolian, and the Negro or Ethiopian ; and to one or other of these all the various forms which the human body assumes in different climates and countries may be referred.

The Caucasan race is distinguished by the oval shape of the head, the softened aspect, and symmetrical harmony of the general person, and the high degree of cultivation of which the intellectual faculties admit. The colour of the skin and of the hair varies. In warm climates the former is dark or olive-coloured, and the latter is black and glossy. In colder regions the skin is fair and light-coloured, or ruddy, and the hair becomes chesnut, fair, or even red.

The Mongolian or Altaic race is distinguished by prominent cheek-bones, flat countenance, oblique eyes, parted by a small interval, straight black hair, slender beard, and olive, tawny, or copper-coloured complexion. This race has formed great empires in China and Japan, and has sometimes extended its conquests beyond the Great Desert; but its civilisation has remained stationary.

The Negro or Ethiopian race is confined to the south of the Atlas. Black complexion, crisp woolly hair, compressed skull, and flat nose, prominent mouth, and large thick or everted lips, form its distinguishing external characters. The tribes of which it consists have ever remained barbarous.

The first of these races, from which Europe, Asia, and the north and east of Africa have been peopled, is denominated Caucasan, because tradition and the natural affinity of nations seem to justify the opinion that this race had originally inhabited the mountainous range between the Caspian and Black Seas, from which it has spread by radiation. In confirmation of this, it may be observed that the tribes of the Caucasus, the Circassians, the Georgians, and the Armenians, afford at the present hour the most perfect and beautiful specimens of the human form. This race may be distinguished, by the analogy of languages spoken by them, into three principal branches.

1. The Aramaean or Syrian branch, proceeding to the south, gave birth to the Assyrians, the Chaldeans, the Arabs ever unsubdued, and who, after Mahomet, aspired at the sovereignty of the world; the Phoenicians, the Jews, the Abessins, colonies of the Arabs, and probably the Egyptian or Koptic race. From this first branch, ever prone to mysticism, the most extended forms of religious belief have issued. Science and literature, occasionally flourishing among them, have, nevertheless, beep always disguised or corrupted by fanciful ceremonials and a style highly figurative.
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2. The Indian, German, and Pelasgic branch was much earlier divided into tribes, and much more extensively diffused. The most numerous affinities may nevertheless be traced between its four principal languages,— the Sanscrit, at present the sacred language of the Hindoos, and the parent of all the dialects of Hindostan; the ancient language of the Pelasgi, the common parent of the Greek, the Latin, of many extinct languages, and of all the present dialects of southern Europe; the Gothic or Tudesc, from which are derived the languages of the north and north-west, for instance the German, Dutch, Anglo-Saxon, and English, the Danish, Swedish, and their dialects; lastly, the Sclavonian, from which are sprung the languages of the north-east, the Russ, the Polish, the Bohemian, and the Vend.

By this branch of the Caucasan race, philosophy, the sciences, and the arts, have been carried to the highest degree of perfection; and of these they may be regarded as the chief depositaries. In Europe this race is believed to have been preceded by the Celtae or Titano- Celtae, whose tribes, proceeding by the north, and formerly very extensive, were nevertheless confined to the most western points; and by the Cantabrians, who passed from Africa to Spain, and who are now almost lost among the numerous nations, the posterity of which is mingled in the European peninsula. The ancient Persians are derived from the same source as the Indians; and their descendants still bear the most conspicuous marks of connection with the European nations.

3. The Scythian and Tartar branch, bending first to the north and north-east, always erratic in the immense plains of these countries, have returned only to ravage the happier establishments of their brethren. From this branch issued the Scythians, who anciently distinguished themselves by inroads into Upper Asia; the Parthians, who destroyed the Greek and Roman dominions; the Turks, who subverted that of the Arabs, and subdued in Europe the last remnant of the Hellenic nation. The Fins and Hungarians are tribes of the same family disseminated among the Sclavonian and Judaic nations. The north and east of the Caspian, their native soil, still maintains tribes which have the same origin and speak similar languages; but they are intermingled with numerous other small septs of different origin and speech. The Tartar tribes remained more unchanged in that tract from which they long threatened Russia, which has at length subdued them, from the mouths of the Danube to beyond the Irtish. Their blood, nevertheless, has been mixed with that of the Mongols, many traces of which may be seen in the younger Tartars.

On the east of this Tartar branch of the Caucasan race begins the Mongolian, which thence extends to the shores of the Eastern Ocean. Its branches, still nomadic, the Calmucks and the Kalkas, roam the Great Desert. Three times have their ancestors, under Attila, Gengis, and Timour, spread the terror of their name among the settled inhabitants of Europe and Asia. The Chinese constitute the branch most early civilized, not only of this race, but of known nations. The Mantchoux, a third branch, who recently conquered, still retain, China. To the same race in great part belong the Japanese and the Coreans, and almost all the hordes which stretch to the north of Siberia, under the sway of the Russians. Excepting some learned Chinese, the whole Mongolian race are attached to the sects addicted to the worship of Fo.

The origin of this great race appears to be in the mountains of the Altaic range, as that of the Asio-Euro-pean is in the elevation of Caucasus. It is impossible, however, to trace the filiation of its branches with the same accuracy. The history of these nomadic nations is as transitory as their establishments; and that of the, Chinese, confined to the bosom of their empire, furnishes only short and unconnected views of the contiguous nations. The affinities of their modes of speech are further too little known to guide us in this labyrinth.

The languages spoken in the north of the Ultra-Gan-getic peninsula, as well as that of Thibet, present some relations, at least in monosyllabic character, with the Chinese; and the nations by whom they are spoken are not void of features of physical resemblance to the other Mongolian tribes. The south of this peninsula, however, is inhabited by the Malays, a much handsomer race, whose breed and language have spread to the coasts of all the islands of the Indian Archipelago, and have occupied the greater number of those of the South Sea. In the largest of the former, especially in the wildest places, dwell other tribes, with crisp hair, black complexion, and negro features, all extremely barbarous. The best known are denominated Papous, which may be applied to the whole.

Neither the Malays nor the Papous can be readily referred to any one of the three great races. The former it is difficult to distinguish from the neighbouring races on each side the Caucasan Indians and the Mongolian Chinese. The Papous may be negroes anciently cast away in the Indian Seas; but to determine this point we require both accurate figures and descriptions.

The inhabitants of the north of the two continents, the Samoieds, the Laplanders, and the Esquimaux, spring, according to some, from the Mongolian breed; according to others, they are degenerate slips of the Scythian and Tartar branch of the Caucasan breed.

The Americans have not yet been clearly traced either to one or other of the races of the ancient continent; yet they are void of character sufficiently precise and constant to constitute a peculiar race: their copper-coloured skin is inadequate: by the dark hair and slender beard they approach to the Mongols; but from these again they are distinguished by the well-marked features and the prominent nose. The modes of speech are as numerous as their tribes; and neither between themselves nor with those of the ancient world has any satisfactory analogy been traced.

Of the various breeds now enumerated, the Caucasan or Asio-European is supposed to furnish the most perfect model of the human frame; and from this, therefore, anatomists derive their descriptions both of the body at large and of individual parts and organs.

The structure of the human body may be studied in two modes, either as an assemblage of organic substances endowed with characteristic physical and vital properties, or as an assemblage of organs destined to effect particular and definite purposes.

The human body, like that of every other mammiferous animal, consists of several kinds of animal organic substances endowed with appropriate characters and properties. The substances thus distinguished have been named elementary textures, since into them, as into so many elements or integrant principles, the human body is supposed capable of being resolved. To enumerate these elementary textures, to ascertain their minute structure or organization, to investigate their distinctive properties, and to determine the extent to which they enter into the composition of particular organs, is the province of General Anatomy. In this department the anatomist, abstracting from the shape, position, and mechanical configuration of parts, studies only their intimate and distinctive characters as organic substances.
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The human body may further be regarded as an assemblage of organs, and sets of organs, destined to effect certain purposes. These purposes may be referred to two general heads; those which are common to plants and animals, and those which are proper to the latter. The first comprehends nutrition and generation, and have been named vital, organic, or automatic functions; the second embraces muscular action, sensation, and nervous influence or innervation, and are distinguished as animal functions. Since these purposes are effected by certain processes going on successively and simultaneously by the action of one or more organs, they are distinguished by the general name of functions, or orders of functions. Each function consists of several integrant and individual processes; every process consists of one or more actions; each action depends on certain properties; and properties in living bodies, though mechanical, chemical, or vital, are always connected either with the intimate structure of parts or with the configuration of organs. Thus nutrition is at once termed a function, and is said to consist of the several functions of digestion, absorption, circulation, respiration, and secretion. Generation, on the other hand, is said to be a function consisting of several processes—the formation of germs or ova, the secretion of semen, impregnation, gestation, and exclusion. Of the functions proper to animals, muscular action, modified in various modes, produces locomotion, gesture, voice, and several motions necessary to the performance of nutrition and generation. Sensation may be said in all cases to depend on nervous action and the mechanism peculiar to each species of sensation. Nervous energy, again, may be said to consist of three properties, those of receiving, transmitting, and recognising impressions. Lastly, a form of faculties connected with the immaterial or thinking part of the system peculiar to man constitutes what are named the intellectual functions.

This division of the phenomena of living bodies into certain assemblages or functions, has given rise to a similar division of these bodies into organs. An organ may be defined to be a part of a living body, of a definite shape, consisting of certain parts, composed of various elementary textures, the seat of one or more actions, and placed in a certain position and region. It rarely happens that one organ only is sufficient for the performance of a function. Several are commonly required to concur to the same general purpose; and hence the organs are arranged in classes, sets, or assemblages, according to the functions to which they are subservient. Thus the organs subservient to the function of digestion consist of the teeth, tongue, and mouth, as organs of mastication; the pharynx and oesophagus as the tube of deglutition; the stomach as the organ of chymification; the duodenum and small intestines as that of chylification; and the large intestines as the temporary receptacle of the exerementi-tial residue of food and drink. Such assemblages of organs have received, for want of better, the denomination of apparatuses; and the anatomist, when he designates a class of organs devoted to the performance of a specific function, is compelled to distinguish them as the apparatus of digestion, the apparatus of absorption, of circulation, of respiration, of secretion, and so forth. To this method of distinction it may indeed be objected, that scarcely in one instance are all the organs of any apparatus exclusively directed to the performance of the function of that apparatus; and an organ concerned in the function of digestion may also contribute to that of circulation or respiration. Thus the larynx, though more particularly the organ of voice, is also an organ of respiration; the tongue and teeth, though belonging in one sense to the organs of digestion, are not less important as those of speech; the diaphragm and abdominal muscles, though organs of respiration, are also accessary agents of digestion. These, however, are only to be regarded as examples of the ingenuity with which one organ in the animal body is made to answer several purposes; and since all arrangements are artificial, or bear relation, not to the purpose of construction, but to the mind of the observer, the best course is to choose that which is least so, and which makes the nearest approach to the apparent objects of nature.

To acquire a just knowledge of the organs of the human body, with the views now stated, it is requisite to study their external shape and configuration, their position and contiguous relations, their ordinary size and dimensions, the mechanical divisions of which they consist, their external characters and physical properties, their intimate structure and the elementary textures of which they are composed, their chemical constitution, their vital properties and consequent actions, and the uses to which they are obviously applied. The history of the organs, arranged upon these principles, constitutes the business of Descriptive, Particular, or Special Anatomy. The term Topographical Anatomy, which has also been proposed, is inadequate, since it indicates one class only of facts,—those belonging to local relations. That of Morphology is equally objectionable. The term Organology, though preferable by reason of greater generality, is not sufficiently appropriate to justify its adoption, to the exclusion of the one already in general use.

GENERAL ANATOMY.

The human body consists of solid and fluid substances, the former of which are organized, and determine the shape of the body and its parts. These organized solids are not in a strict physical sense solid and impenetrable. Most of them are soft, compressible, and elastic, by reason of the fluid matter contained in their interstices; and when deprived of this by desiccation, they shrink in various degrees, and lose both bulk and weight. The general ratio of the fluid to the solid parts has been already stated to vary from 7 to 1, to 9 to 1. An adult carcass weighing perhaps from 9 to 10 stones, has been reduced by desiccation to 7⅜ lbs. In short, a human body may be reduced to nearly the weight of its skeleton, which varies from 150 ounces =9⅜ lbs. to 200 ounces = 12 1 /2 lbs.

These organized solids agree in the possession of certain general characters. Their internal structure appears to consist of a union of solid and liquid matter, which is observed to exude in drops more or less abundant from the surface of sections. The solid parts are generally arranged in the form of collateral lines, sometimes oblique, sometimes perfectly parallel, sometimes mutually intersecting. Such lines are denominated fibres, and occasionally filaments. In other instances the solids are observed to consist of minute globular or spheroidaI particles, connected generally by delicate filaments. Most of these solids anatomists and miscroscopical observers have attempted to resolve into what they conceive to be an ultimate fibre or last element; but this inquiry leads beyond the bounds of strict observation.

Most of the solids may be demonstrated to be penetrated[7:2:712] by minute ramifying tubes or blood-vessels, which traverse their substance in every direction, and in which is contained the greater part, perhaps the whole, of the fluid matter found in the solids. In a few in which ramifying vessels cannot be positively demonstrated, their existence is inferred by analogy from those in which they can. The filamentous, fibrous, or globular arrangement, with the distribution of arborescent vessels, constitutes organization. The substances so constructed are named organized tissues (teloe, textus), or textures, or simply tissues.

The organized solids also resemble each other in chemical constitution. They may be resolved into proximate principles, either the same or very closely allied. The proximate principles most generally found are albumen, fibrin, and gelatine, one or other of which, sometimes more, form the basis of every tissue of the human body. Next to these are mucus, and oily or adipose matter. Osma-zome or extractive matter is mund in certain tissues. And lastly, several saline substances, as phosphate of lime, carbonate of lime, soda, hydrochlorate of soda, are found in variable proportions in most of them. Of these principles albumen and fibrin, which are closely allied and pass into each other, are the most common and abundant. Osmazome, which is probably a modification of fibrin, is less frequent. These also are contained in the blood, and probably derived from that fluid. Gelatine, though not found in the blood, is nevertheless a principle of extensive distribution, being found in skin, cellular tissue, tendon, cartilage, and bone. These proximate principles are resolved, in ultimate analysis, into carbon, oxygen, hydrogen, azote, phosphorus, and sulphur. From the saline substances, calcium, potassium, sodium, chlorine, iron, and manganese may be obtained.

The organized solids which enter into the composition of the human body, though agreeing in the characters now mentioned, differ nevertheless in other respects. The most remarkable differences of this kind consist in peculiarities in the arrangement of their constituent fibres, peculiarities in the nature of these fibres, and different proportions or modifications of their proximate chemical principles. From one or other of these circumstances the organized solids may be referred to the following 17 elementary tissues:—Filamentous or cellular tissue, including ordinary cellular membrane and adipose membrane; artery, vein, with their minute communications, termed capillary vessels, and the erectile vessels; lymphatic vessel, and gland; nerve, plexus, and ganglion; brain, or cerebral matter; muscle; white fibrous system, including ligament, periosteum, and fascia; yellow fibrous system, including the yellow ligaments, &c. bone and tooth; gristle or cartilage; fibro∙∙cartilage; skin; mucous membrane; serous membrane; synovial membrane; and lastly, glandular structure, or the peculiar matter which forms the liver, the pancreas, the kidneys, the female breast, the testicle, and other organs termed glands.

These tissues may be distinguished into orders, according to the mode of their distribution in the animal frame. Several, for instance filamentous tissue, artery and vein, lymphatic vessel, and nerve, are most extensively distributed, and enter into the composition of all the other simple tissues. To these, therefore, which are named by Bichat general or generating systems, the character of textures of distribution may be applied. A second order, consisting of substances confined to particular regions and organs, and placed in determinate situations, viz. brain, muscle, white fibrous system, yellow fibrous system, bone, cartilage, fibro-cartilage, and gland, may be denominated particular tissues. To a third order, consisting of substances which assume the form of a thin membrane, expanded over many different tissues and organs, may be referred skin, mucous membrane, serous membrane, and synovial membrane, under the denomination of enveloping tissues. It may indeed be objected, that the circumstance of mechanical disposition is insufficient to communicate a distinctive or appropriate character, and several of the tissues referred to the second head, e. g. fascia, must, on this principle, be referred to the third. The objection is not unreasonable. But it may be answered, that it is almost vain to expect an arrangement entirely faultless; and the present is convenient in being on the whole more natural, and therefore more easily remembered, than any other. A distinct idea of it may be formed from the following tabular view.
[table]

The fluids of the animal body are various, but may be distinguished into three sorts; the circulating nutritious fluid named the blood, the fluids which are incessantly mixed with the blood for its renewal, and those which are separated from it by secretion.

The blood is well known to be a viscid liquid, of red colour, peculiar odour, and saline, something nauseous taste. Its temperature in the living body is about 97°; its specific gravity is about 105 to water as 100. Its quantity is in the adult considerable, varying from 8 or 10 to 80 or 100 pounds.

According to the results of microscopic observation it consists of red particles suspended in a serous fluid. On the shape of these red particles various opinions have been maintained. Generally represented as globular, Hewson describes them as flattened spheroids, or lenticular bodies, a view which is partly confirmed by the observations of Prevost and Dumas, and also of Bedard. The opinion of Home and Young, that the flattening of these globules is a process posterior to the discharge of the fluid, is not improbable. These particles have indeed since the time of Hewson been almost universally represented as consisting of a central transparent whitish globule, inclosed in a red translucent vesicle, which gives them the shape of an oblate spheroid. The diameter of these particles is estimated, by the subdivided scale of Kater, the micrometer of Wollaston, and the eriometer of Young, at, +θ, and by the common micrometer, at - r7 ⅛θ of an inch. (Phil. Trans.) This description applies to the blood circulating in the vessels.

Discharged from the vessels, it exhales, during the process of cooling, a thin watery vapour, consisting of water suspending animal matter capable of impressing the sense of smell, and undergoing decomposition. During the same [7:2:713] space it is observed to be converted into a firm mass, which, though still soft and elastic, is entirely void of fluidity. As this process advances, a thin watery fluid, straw-coloured, not perfectly transparent, is observed to exude from every part of the solid mass, which also diminishes in size, till at length it is found floating like a tolerably thick cake in the thin watery fluid. The thick solid mass is named the clot or coagulum; the watery fluid is denominated serum; and the process of the separation, which is spontaneous, is termed coagulation. The blood at the same time is said to discharge carbonic acid.

The clot, if divided and washed in water often changed, or in alcohol or aqua potasses, may be deprived of its red colour, and made to assume a gray or bluish-white tint. This gray mass, which is tough, coherent, opaque, and more or less dense, homogeneous, but void of traces of organic structure, consists chiefly of albumen or fibrin, or a substance partaking of several of the characters of both. To this substance the blood owes its viscidity and its property of spontaneous coagulation; and from the circumstance of its resemblance to the lymph or albuminous fluid which is effused from wounds and inflamed surfaces, and to the fibrin of muscle, and the albumen of many of the tissues, it may be regarded as the most vital and nutritious part of that fluid. It is a mistake nevertheless to assert, as is done by Bedard and others, that this substance presents to the microscope the aspect and structure of muscular fibre. Its aspect is by no means so regular as this, nor can its particles be said to present tracés of organic structure or arrangement.

The red matter removed by washing is a mixture of serum, of globules, and of a peculiar colouring matter. Modern chemistry shows that the latter is a particular substance, insoluble in water, but susceptible of suspension in it to an extreme extent, and consisting of animal matter combined with peroxide of iron. It is distinguished by the name of zoohematine. Deprived of this, the globules are estimated by Bauer at g- ð¾-ð of an inch in diameter.

The serum, with the taste and odour of the blood, rather alkaline, coagulates at 162° F. or on the addition of acids, nitrate of silver, or corrosive sublimate, and then resembles boiled white of egg. The coagulated matter is albumen; and a little water containing soda and salts of soda may be separated. It is a remarkable difference between this albumen, which is suspended in the serum, and that which constitutes the clot, that while the former requires heat as a re-agent, the latter assumes the solid form spontaneously.

Blood also contains occasionally some oily matter, the presence of which renders the serum opaque and milky.

The colour of the blood varies in different parts of the system. In the left auricle, ventricle, and arterial trunks generally, its colour is bright scarlet, a tint which it loses in the capillary vessels. In the veins, venous trunks, right auricle, right ventricle, and pulmonary artery, its colour is a dark or purple-red, or modena. As it moves from the trunk and branches through the minute divisions of the pulmonary artery, it gradually parts with this tint; and in the branches of the pulmonary veins it is found to have acquired the bright scarlet colour which it has in ∙'.e left auricle, ventricle, and aorta. Hence the modena or dark-coloured blood is distinguished as venous, or proper to the veins; and the bright red or scarlet-coloured as proper to the arteries.

In the foetus, the blood contains little coagulable matter; and this principle is entirely wanting in the blood of the menstrual discharge.

The fluids received by the blood are chyle and lymph. Chyle is derived from chyme, a gray pulpy substance, formed from the alimentary mass in the stomach and duodenum. Detached from this substance, and received by the chyliferous tubes, it is whitish and scarcely coagulable. In the mesenteric glands it becomes more coagulable, and assumes a rose colour. Lastly, in the thoracic duct, and before joining the mass of blood, it is distinctly rose-coloured, coagulable, and globular in its particles. In the branches of the pulmonary artery it appears to become perfect blood. Lymph is a colourless, viscid, albuminous fluid, imperfectly known.

Of the fluids separated from the blood, all cannot be said to belong to the animal body. Several, for instance the perspired fluid of the skin and lungs, the fluid of the cutaneous and mucous follicles, and the urine, become, after secretion, foreign to the body, and require to be removed. Those belonging to the body are such as are prepared for some purpose within it, and after this are either re-absorbed, or, being decomposed, are expelled. Of the former kind, fat, serum of serous membranes, and synovia, afford examples. To the latter description belong tears, saliva, pancreatic fluid, bile, the seminal fluid of the male, and the milk of the female, all of which are the result of a distinct glandular secretion for a specific purpose, after which they are expelled from the economy. The urine, though also the result of glandular secretion, is nevertheless exempt from this rule, and though separated from arterial blood, is forthwith eliminated. Its chief purpose seems to be to afford a convenient vehicle for ridding the system of superfluous azote, and to maintain the due proportion between this and the other ultimate principles, carbon, hydrogen, and oxygen. The fluids which fulfil a purpose in the economy are regarded as secretory, and are remarkable for a predominance of alkali; those which do not are excrementitial, and are generally acid.

BOOK I.

CHAP. I.—THE COMMON TISSUES.

Filamentous or Cellular Tissue. (Tela Cellulosa, — Tissu Cellulaire,— Tissu Muqueux of Bordeu,— Corpus Cribrosum Hippocratis,— Corps Cribleux of Fouquet,— Reticular Membrane of William Hunter.)

The general distribution of the filamentous or cellular tissue was first maintained by Haller and Charles Augustus de Bergen, and afterwards made the subject of elaborate discussion by William Hunter and Bordeu. It may be described as a substance consisting of very minute thready lines, which follow no uniform or invariable direction, but which, when gently raised by the forceps, present the appearance of a confused and irregular net-work. As these minute lines cross each other, they form between them spaces of a figure not easily determined, and perhaps not uniform. By some authors these spaces or intervals have been named cells; but, accurately speaking, the term is not fortunately applied. The component lines, which do not exceed the size of the silk-worm threads, are so slender, that they do not form those distinct partitions which the term cell implies; and though by forcible distension, such as takes place in insufflation, or separation by forceps, cavities appear to be formed, these, it will be found, are artificial, and result from the separation of an infinity of the slender filaments of which the part is composed. These interlinear spaces necessarily communicate on every side with each other; and indeed the most distinct[7:2:714] way of forming a true idea of the structure of the cellular tissue, is to suppose a certain space of the animal body which is divided and intersected into an infinite multitude of minute spaces (areolae) by slender thready lines crossing each other. This description, derived from personal observation, renders the name of filamentous more appropriate to this tissue than that of cellular, by which it is generally known.

The interstitial spaces resulting from the interlacement of these filaments do not exist as distinct cavities in the healthy state, so that they cannot be said to contain any substance solid or fluid. But when an incision is made into this tissue in the living body, it is found, that if we except those fluids which issue from divided vessels, nothing is observed to escape but a thin exhalation or vapour, which is evidently of an aqueous nature. This is what some authors have termed, from its resemblance to the serous part of the blood, the cellular serosity (Bichat), and the quantity of which has been greatly exaggerated. In the living body it appears not to exist as a distinct fluid, but merely as a thin vapour, which communicates to the tissue the moist appearance which it possesses.

This fluid is understood to be derived from the minute colourless capillaries named exhalants; and it is supposed to be no sooner poured forth in an insensible manner, than it is removed by the absorbing power of lymphatics, minute veins, or both. It is further believed, that whatever serous fluid is secreted into the interstitial spaces or cells of the filamentous tissue, is in the healthy state speedily removed; so that exhalation implies absorption; and the filamentous tissue is therefore represented as the seat of incessant exhalation and absorption.

The serous fluid of the filamentous tissue varies in quantity in different regions. In the cellular tissue of those parts which are free from fat, as in the eyelids, the prepuce, the nymphee and labia, and the scrotum, it is said to be more abundant than in others. The peculiar structure of those parts, which is cellular, may render any excess of serous fluid more conspicuous; for it is matter of observation, that in many persons otherwise healthy these parts are not unfrequently distended with serous fluid. On the other hand, it must be remarked that the submucous cellular tissue, and that which surrounds arteries, veins, and excreting ducts, which is delicate in substance and compact in structure, contains but a small proportion of serous fluid, and does not readily admit its presence.

This fluid has been generally said to be of an albuminous nature; and if it be identical with the serum of the blood, from which it is believed to be secreted, this character is not unjustly given it. Bichat, who maintained this opinion, injected alcohol into the filamentous tissue of an animal previously rendered emphysematous, and found in various parts whitish fiocculi, which he regarded as coagulated albumen. He also obtained the same result by immersing a portion of the scrotum in weak nitric acid; and when a considerable quantity of this tissue was boiled, it furnished much whitish foam, which Bichat regarded as albuminous.^[13. Anatomie Générale, tom. i. p. 5O. ] These experiments, however, are liable to this objection, that the effects in question may have arisen from coagulation of part of the filamentous tissue itself, which contains a considerable proportion of albuminous matter. The best mode of determining the point is to obtain the fluid apart, and to try the effects of the usual tests on it when isolated from the tissue in which it is lodged.

The description here given applies to the proper filamentous tissue. This substance was shown by Ruysch, and afterwards by William Hunter and Maseagni, to be penetrated by arteries and veins. Exhalants, absorbents, and nerves, it is also said to receive. The arteries certainly belong in the healthy state to the order of colourless capillaries, which are nearly the same with exhalants. It does not appear that the nervous twigs observed to pass through this tissue are lost in it; for in general they have been traced to some contiguous part.

Such are the general properties of this tissue, considered as an elementary organic substance extensively diffused through the body. In particular regions it undergoes some modifications, which may be referred to the following heads :—1. beneath the skin, or rather under the adipose membrane—the subcutaneous and intermuscular cellular tissue; 2. beneath the villous or mucous membranes —the submucous cellular tissue; 3. beneath the serous membranes—the subserous cellular tissue; 4. round bloodvessels, excreting ducts, or rather organs—the inclosing tissue, vascular sheaths, &c.; 5. in the substance of organs—the penetrating cellular tissue.

The situation of the subcutaneous filamentous tissue deserves particular notice. Though generally represented as below the skin, it is not immediately under this membranous covering. The skin rests on the adipose membrane, beneath which again is placed the filamentous tissue, extending like a web over the muscles and bloodvessels, penetrating between the fibres and bundles of the former, surrounding the tendons and ligaments, and connected by these productions with a deep-seated layer, on which the muscles move, where they do not adhere to the periosteum and to bones.

The extensive distribution of the subcutaneous filamentous tissue, the mutual connection of its parts, and its ready communication with the filamentous tissue of the mucous and serous membranes, were demonstrated by Haller, William Hunter, and Bordeu, and have been clearly explained by Portal and Bichat. The principal points worthy of attention may be stated in the following manner.

The filamentous tissues of the head and face communicate freely with each other, and with that of the brain by the cranial openings, and with the submucous tissue of the eyelids, nostrils, lips, and the inner surface of the mouth and cheeks. It communicates also with the subcutaneous tissue of the neck all round; and at the angle of the jaw, in the vicinity of the parotid gland, is the common point of re-union. To this anatomical fact is referred the frequency of swellings and purulent collections in the region of the parotid in the course of various diseases of the head, face, and neck.

The filamentous tissue of the neck may be viewed as the connecting medium between that of the head and trunk. From the former region it may be traced downwards along the back, loins, breast, sides, flanks, and belly. At the cervical region, and between the shoulders, it is dense and abundant; and, surrounding the dorsal part of the vertebral column, it is connected with the mediastinal tissue, the submucous tissue of the lungs, and the subserous tissue of the costal pleura. At the fore part of the neck it is in like manner connected with the abundant tissue of the pectoral region, and by means of that surrounding the larynx and trachea, lst, with the submucous tissue of the bronchi; and, 2d, with the anterior mediastinum. Passing downwards, the same communication may be traced with the intermuscular tissue [7:2:715]of the loins and belly, the tissue surrounding the lumbar and sacral portion of the vertebral column, that connecting the mesentery and large vessels to the vertebrae, and extending all round under the muscular peritoneum, and into the pelvis, where, by means of the tissue at the posterior surface of the abdominal muscles, at the anterior surface of the iliavus internus, and through the obturator hole and ischiadic notch, it communicates with the filamentous tissue of the lower extremities. From the rectum and branches of the ischium it is continued along the perineum by the urethra, and into the scrotum.

In the whole of this course, it is abundant in the space before the vertebrae, round the psoae and iliacus internus muscles, and round the bladder, rectum, prostate gland, and womb. The tissue surrounding the vertebral column communicates with that in the interior of the column by the intervertebral holes.

The armpit may be considered as the point of union between the filamentous tissue of the trunk and that of the upper extremities, while the groin is the corresponding spot for the lower extremities. These facts should be kept in mind in observing the phenomena of diseases of this tissue.

Notwithstanding this general connection, however, certain parts of the tissue are so dense and close as to diminish greatly the facility of communication. Thus, along the median line it is so firm, that air injected invariably stops, unless impelled by a force adequate to tear open its filaments; and water is rarely found effused in this situation. In the neighbourhood of some parts of the skeleton also, as at the crest of the ilium, over the great trochanter, and on the shin, the filamentous tissue is very dense and coherent.

In chemical composition it consists principally of gelatine, but contains some albuminous matter.

Adipose Tissue. (Tela Adiposa, —Tissu Adipeux,—Tissu Graisseux.)

The separate existence of an adipose membrane was suspected by Malpighi, maintained by De Bergen and Morgagni, and demonstrated by William Hunter. It was, however, confounded with the filamentous tissue, under the general name of cellular membrane, adipose membrane, and cellular fat, by Winslow, Portal, Bichat, and most of the continental anatomists, till distinguished and described by Μ. Bedard.

According to the dissections of De Bergen and Morgagni, the demonstrations of Hunter, and the observations of Bedard, its structure consists of rounded packets or parcels (pelotons) separated from each other by furrows of various depth, of a figure irregularly oval, or rather spheroidal, varying in diameter from a line to half an inch, according to the degree of corpulence and the part submitted to examination. Each packet is composed of small spheroidal particles, which may be easily separated by dissection, and which are said to consist of a cluster of vesicles still more minute, and agglomerated together by delicate cellular tissue. The appearance of these ultimate vesicles is minutely described by Wolff in the subcutaneous fat, and by Monro and Clopton Havers in the marrow of bones, in which the last two authors compared them to strings of minute pearls. If the fat with which these vesicles arc distended should disappear, as happens in dropsy, the vesicles collapse, their cavity is obliterated, and they are confounded with the contiguous cellular tissue, without leaving any trace of their existence.

Hunter, however, asserts, that in such circumstances the cellular tissue differs from the tissue of adipose vesicles, in containing no similar cavities; and justly remarks that the latter is much more fleshy and ligamentous than the filamentous tissue, and contends, that though the adipose receptacles are empty and collapsed, they still exist. When the skin is dissected from the adipose membrane it is always possible to distinguish the latter from the filamentous tissue, even if it contain no fat, by the toughness of its fibres, and the coarseness of the web which they make.

The distinguishing characters between the cellular or filamentous and the adipose tissue may be stated in the following manner :—1sZ, The vesicles of the adipose membrane are closed all round, and, unlike cellular tissue, they cannot be generally penetrated by fluids which are made to enter them. If the temperature of a portion of adipose membrane be raised by means of warm water to the liquefying point of the contents, they will remain unmoved so long as the structure of the vesicles is not injured by the heat. If, again, an adipose peloton be exposed to a solar heat of + 40 centigr. though the fat be completely liquefied, not a drop escapes until the vesicles are divided or otherwise opened, when it appears in abundance. The adipose matter, therefore, though fluid or semifluid in the living body, does not, like dropsical infiltration, obey the impulse of gravity. 2d , The adipose vesicles do not form, like cellular tissue, a continuous whole, but are simply in mutual contiguity. This arrangement is demonstrated by actual inspection, but becomes more conspicuous in the case of dropsical effusions, when the filamentous tissue interposed between the adipose molecules is completely infiltrated, while the latter are entirely unaffected. 3⅛ The anatomical situation of the adipose tissue is different from that of the filamentous tissue. The former is found, Isŕ, in a considerable layer immediately beneath the skin; 2d , between the peritoneal folds which form the omentum and mesentery; 3d, between the serous and muscular tissues of the heart; and, 4∕∕z, round each kidney.

In each of these situations it varies in quantity and in physical properties. In the least corpulent persons a portion of fat is deposited in the adipose membrane of the cheeks, orbits, palms of the hand, soles of the feet, pulp of the fingers and toes, flexures of the joints, round the kidney, beneath the cardiac serous membrane, and between the layers of the mesentery and omentum. In the more corpulent, and chiefly in females, it is found not merely in these situations, but extended in a layer of some thickness almost uniformly over the whole person; and is very abundant in the neck, breasts, belly, nions veneris, and flexures of the joints.

Besides the delicate cellular tissue by which the packets and vesicles arc united, the adipose tissue receives arterial and venous branches, the arrangement of which has been described by various authors, from Malpighi, who gave the first accurate account, to Maseagni, to whom we are indebted for the most recent. According to the latter, who delineates these vessels, the furrow or space between each packet contains an artery and vein, which, being subdivided, penetrate between the minute grains or particles of which the packet is composed, and furnish each with a small artery and vein. The effect of this arrangement is, that each individual grain or adipose particle is supported by its artery and vein as by a foot-stalk or peduncle, and that those of the same packet are kept together, not only by contact, but by the community of ramifications from the same vessel. These grains are so closely attached, that Maseagni, who examined them with a good lens, compares them to a cluster of fish-spawn. Grutz-macher found much the same arrangement in the grains and vesicles of the marrow of bones.
[7:2:716]

It has been supposed that the adipose tissue receives nervous filaments; and Maseagni conceives-he has demonstrated its lymphatics. Both points, however, are so problematical, that of neither of these tissues is the distribution known.

The substance contained in these vesicles is entirely inorganic. Always solid in the dead body, it has been represented as fluid during life by Winslow, Haller, Portal, Bichat, and ' most authors on anatomy. The last writer indeed states, that under the skin it is more consistent, and that in various living animals he never found it so fluid as is represented. The truth is, that in the human body, and in most mammiferous animals during life, the fat is neither fluid nor semifluid. It is simply soft, yielding, and compressible, with a slight degree of transparency or rather translucence. This is easily established by observing it during incisions through the adipose membrane, either in the human body or in the lower animals.

The properties and composition of fat form a subject for chemical rather than anatomical inquiry; and in this respect its nature has been particularly investigated by Μ. Chevreul. According to the researches of this chemist, fat consists essentially of two proximate principles, stearine (orτεαg, sebum, sapo), and elaine (ελαιοv, oleum). The former is a solid substance, colourless, tasteless, and almost inodorous, soluble in alcohol, and preserving its solidity at a temperature of 138° centigrade. Elaine, on the contrary, though colourless, or at most of a yellow tint, und lighter than water, is fluid at a temperature of from 17° to 18° centigrade, and is greatly more soluble in alcohol. Of this substance marrow appears to be merely a modification; and the membranous cavities or medullary membrane in which it is contained may be viewed as an intra-osseous adipose tissue.

Little doubt can be entertained that animal fat is the result of a process of secretion; but it is no easy matter to determine the mode in which this is effected. Malpighi, departing, however, from strict observation, imagined a set of ducts issuing from glands, in which he conceived the fat to be elaborated and prepared. To this he appears to have been led by his study of the lymphatic glands, and inability to comprehend how the process of secretion could be performed by arteries only. This doctrine, however, was overthrown by the strong arguments which Ruysch derived from his injections; and Malpighi himself afterwards acknowledged its weakness and renounced it. In short, neither the glands nor the ducts of the adipose membrane have ever been seen.

Winslow, though willing to adopt the notion of Malpighi, admits, however, that the particular organ by which the fat is separated from the blood is unknown. Haller, on the contrary, aware of the permeability of the arteries, and their direct communication with the cells of the adipose tissue, and trusting to the testimony of Malpighi, Ruysch, Glisson, and Morgagni, that it existed in the arterial blood, saw no difficulty in the notion of secretion, or rather of a process of separation; and upon much the same grounds the opinion is adopted by Portal and others. Bichat, again, contends that no fat can be recognised in the arterial blood, and justly adduces the fact, that none can be distinguished in blood drawn from the temporal artery. The accuracy of this fact is confirmed by subsequent observation. This result is not at variance with the fact observed by Dr Traill, who found oily matter in venous blood in two instances. In wounds in the human body during life, and in living animals, oily particles may be seen floating on the surface of the blood; but these proceed from division of the adipose vesicles.

That fat does not .exist in the arterial blood may be therefore admitted as an established point. The idea that it is separated or strained from this fluid, therefore, must also be gratuitous; and as such it is viewed by Bichat, who considers the deposition of fat as the effect of exhalation, which is little more than a different name for the process termed by Haller secretion. Lastly, an opinion has been delivered by Maseagni, that while the arteries depositor pour forth an imperfect or crude oily fluid, the lymphatics absorb the thin parts, and leave the residue in a more solid and perfect form. In conclusion, all that can be affirmed regarding the formation of this substance is, that it is deposited by the blood-vessels, but by what particular process, or in what form, is entirely unknown. The process by which the arteries of the adipose membrane secrete fat appears to be equally mysterious as that by which the vessels of muscle deposit fibrin, those of bone deposit osseous matter, and those of cartilage form that animal substance.

Artery, Arterial Tissue. (Arteria, —Tissu Arteriel.)

The structure of the arteries has been so much the subject of examination at all periods of the history of anatomy, that to mention the authors by whom it has been .described would be much the same as to enumerate all the anatomists who have ever written. To omit Galen, and some of those who wrote shortly after the revival of literature, descriptions of the structure of arteries have been given with different degrees of minuteness and accuracy by Willis, Vieussens, Verheyen, Lancisi, Bidloo, the first Monro, Morgagni, Ludwig, Haller, Delasone, Bichat, Gordon, Magendie, and by Mondini. Yet the descriptions given by these observers are discordant, and, with the exception of those given by the last four authors, do not accord with the characters which this substance actually presents.

The following account is derived principally from repeated examination of the arteries of the human subject, occasionally compared with those of the more familiar domestic animals.

Every arterial tube greater than one line in diameter is visibly composed of one adventitious and two essential substances: the first, the sheath, reputed to consist of condensed filamentous tissue; the two last, the proper arterial and internal tissues. ( Tunica propria et menιbranα intima.)

1. The inner surface of the arterial tube is formed by a very thin semitransparent polished membrane, which is said to extend not only in the one direction over the inner surface of the left ventricle, auricle, and pulmonary veins, but in the other to form the minute vascular terminations which are distributed through the substance of the different organs. This membrane is particularly described by Bichat under the name of common membrane of the system of red blood, because he believed it to exist wherever red blood was moving,—in the pulmonary veins, in the left side of the heart, and over the entire arterial system.

The inner membrane may be demonstrated by cutting open or inverting any artery of moderate size, when it may be peeled off in the form of thin slips by the forceps. Or, if the tube be fitted on a glass rod, by removing the layers of the proper membrane in successive portions, the inner one at length comes into view in the form of a thin translucent pellicle, of uniform, homogeneous aspect, without fibres or other obvious traces of organization. This membrane is supposed to be prolonged to form those minute vessels in which the proper coat cannot be traced. It is very brittle, and is distinguished during life by a remarkable activity in forming the morbid states to which [7:2:717]arteries are liable. In other respects it is deemed by Bichat peculiar, and, though similar to the proper membrane, is to be considered as unlike any other tissue. Its chemical composition is not known.

2. Exterior to this common or inner membrane is placed a dense strong tissue of considerable thickness, of a dun yellowish colour, which is found to consist of fibres disposed in concentric circles placed contiguous to each other round the axis of the artery. If this substance be examined either from without or in the opposite direction, it will be found that, by proper use of forceps, its fibres can be separated to an indefinite degree of minuteness, even to that of a hair, and that they uniformly separate in the same direction. Longitudinal fibres are visible neither in this nor in any other tissue of the arterial tube. This is the proper arterial tissue; (tunica propria.) Its uniform dun yellow colour is perceived through the semitransparent inner membrane, and is most conspicuous either when this is removed, or when the outer cellular envelope is detached and the component threads separated from each other; and if it be less distinct in the smaller branches, it is because the tissue on which the colour depends is here considerably thinner. In this respect it varies in different regions. Though in general less dense and abundant as the arteries recede from the heart, it is thicker, eaeteris paribus, in those of the lower than in those of the upper extremities. In the vertebral and internal carotid arteries, and in those distributed in the substance of the liver, spleen, &c., it is thinner than in vessels of the same size in the muscular interstices.

The nature of this tissue has been the subject of much controversy. It was long believed to be muscular, and to possess the properties of muscular fibre. Bichat showed that the arguments by which this opinion was supported are inconclusive, and that the arterial tissue has very few qualities in common with the muscular. The circumstances from which he derived his proofs were its physical and physiological properties.

The arguments derived from the physical properties of this tissue are chiefly the following :—The arterial tissue is close, elastic, fragile, and easily divided by ligature; muscular fibre is more loose in structure, by no means elastic; and, instead of being divided or cut by ligature as artery is, undergoes a sort of strangulation. The action of alcohol, diluted acids, and caloric, by means of hot fluids which are not corrosive, affords a proof of the chemical difference of these animal substances. All of them produce in the arterial tunic a species of shrivelling or crispation, which seems to depend on more complete coagulation of one of the chemical principles; but no similar effect takes place in muscular fibres. According to Berzelius, the proper arterial tunic contains no fibrin.^[14. A View of the Progress of Animal Chemistry, by J. J. Berzelius, Μ. D. &c. &c., p∙ 24, 25. ^London, 1813. ] Beclard, however, asserts that he has ascertained that it contains a portion of this principle; but nevertheless hesitates to consider it as a muscular or fibrinous tissue, and expresses his opinion that it would be with greater propriety referred to that order of substances which he has named yellow or tawny fibrous system.

The consideration of the physiological or organic properties leads to similar results. Neither mechanical nor chemical agents applied as stimulants produce any change or motion in the living arterial membrane. 1. The arteries of an amputated limb, exposed the moment after amputation, while the muscles are in active motion, do not contract or move when punctured by the scalpel. 2. The experiments of Bikker and Van-den-Bos with the electric spark, and those of Vassalli-Eandi, Giulio, and Rossi with the galvanic pile, may be considered as disproved by the experiments of Nysten,^[15. Nouvelles Experiences Galvaniques, &c., par P. H. Nysten, &C·, Pan 11, p. 235-6. Paris. Recherches de Physiologie, 1811, p. 307∙ Paris. ] who found no contraction in the human aorta after violent death, while the heart and other muscles could still be excited. In performing the same experiment with the artery of the living dog, this physiologist was equally disappointed. 3. The circular contraction of the calibre of an artery, either partially or wholly divided, depends not on irritability, but either on its elasticity, or on that property which it possesses of contracting strongly the instant the distending agent is removed. This power, which was rather happily named by Bichat contractilité par defaut d’extension, is quite different from muscular contraction or irritability, and must not be confounded with them; but it depends in a degree not much less on the living state of the body and the individual arterial tube. 4. The contraction said to take place in living arteries after the application of alcohol, acids, or alkalies, is to be ascribed to the chemical crispation, and not to stimulant power. It does not relax. 5. These inferences are not inconsistent with the experiments of Thomson, Philips, Hastings, and others, on minute arterial tubes, which may be admitted to possess something like irritability, or rather susceptibility of contraction, without the necessity of supposing the same property in the large branches and trunks. 6. This is so much more probable, as in these minute arteries the proper arterial tunic is either wanting, or is so much thinner and so modified, that it is impossible to conceive its presence capable of affecting the result of experiments made to determine the degree or kind of arterial contraction.

3. The outer surface of the proper arterial tissue is enveloped, as above noticed, in a layer of dense filamentous or cellular membrane, which is very firmly attached to it, and which was formerly considered as part of the arterial tissue. It is adventitious; a modification of filamentous or cellular texture, which establishes a communication between the artery and the contiguous parts, and is necessary to the nutrition and healthy state of the vessel. It incloses and transmits the minute vessels anciently denominated vasa vasorum (arteriolae arteriarum, Haller); and if detached even through a trifling extent, the arterial portion thus divided is sure to become dead, to be affected with inflammatory and sloughing action, and ultimately to give way and discharge the contents of the vessel. Μ. Bcclard considers it a fibro-cellular membrane, which may in the larger arteries be divided into two layers; one exterior, similar to the general filamentous tissue; the other inside, between the outer layer and the proper tissue, yellowish and firm, but still sufficiently distinct from the proper tunic. In the cerebral arteries it is wanting, and in most parts of the chest and belly its. absence is supplied by a portion of pericardium, pleura, or peritoneum. Yet even there a thin layer of fine cellular tissue appears to connect these membranes to the proper tunic. In the extremities the cellular sheath is removed in dissecting arterial preparations.

At different periods several anatomists have maintained the existence of longitudinal fibres in arterial tissue; and even at the present day this notion is not entirely abandoned. Morgagni was the first who, trusting to mere observation, the only sure guide in anatomical science, doubted the existence of these fibres, and was not ashamed to say he was unable to perceive them.^[16. Adversaria Anatomica, tom. ii. p. 78∙ ] Upon the same [7:2:718]ground Haller would not admit their existence;^[17. “Verum anatome et microscopium omnino fibras longitudinem sequentes nunquam demonstravit, aut mihi, aut aliis ante me scriptoribus, quorum auctoritate meam tueor.” (Elementa Physiologice, lib. ii. sect. 1, § 7∙) ] and Bichat and Meckel positively deny them. I have repeatedly examined almost every considerable artery of the human body, and I have never been able to recognise any longitudinal fibres, either in the middle or proper coat, or in the thin internal membrane, as taught by Willis, Douglas, and Delasone.

Though arterial tissue does not appear to be very vascular, it is furnished with arteries and veins (vasa vasorum, arterioles arteriarum), which do not come from the artery or vein itself, but from the neighbouring vessels.^[18. Hunter, sect. iv. p. 131. ] Thus the aorta at its origin is supplied with minute arteries from the right and left coronary, and in some instances with a proper vessel adjoining to the orifice of the right coronary artery, which Haller regards as a third coronary. The rest of the thoracic aorta derives its vessels from the upper bronchials, from twigs of the internal mammary arteries, from the bronchials, from the oesophagcals, and from the phrenics. The abdominal portion is supplied from the spermatics, the lumbar, and in some instances the mesocolic artery. The same arrangement nearly is observed with regard to the veins.

Few textures are more liberally supplied with nerves than arteries are. Almost every considerable trunk or vessel is surrounded by numerous plexiform filaments of nerves, many of which may be traced into the tissue of the artery. The anterior part of the arch of the aorta is abundantly supplied with branches from the superficial cardiac nerves, which Haller was unable to trace beyond the artery. The coeliac, the mesenteric, and the mesocolic arteries are invested with numerous plexiform nervous filaments derived from the large semilunar ganglion of the splanchnic nerve. The renal arteries in like manner are surrounded by numerous twigs of the renal plexus; and each of the intercostal arteries at its origin receives nervous threads from the intercostal nerves. This arrangement, which is observed chiefly in the blood-vessels going to the internal organs, led Bichat to announce it as a general fact, that the arteries derive their nerves almost exclusively from the ganglions and the gangliar nerves.^[19. “Le grand arbre à sang rouge ou l’artériel est presque exclusivement embrassé par la première classe des nerves.” (Armerait Générale, tom. i. p. 302.) ] The inference does not rest upon strict observation, and evidently owes its birth to the hypothetical opinions of this ingenious physiologist. All the arteries going to the extremities, the axillary, and iliac, and their branches, receive nerves from the neighbouring nervous trunks, which are formed chiefly from cerebral or spinal nerves, and have no immediate connection with the system of the ganglions. In the internal carotid and the vertebral arteries, and their branches, nerves cannot be distinctly traced.^[20. ĮI. A. Wrisberg, De Nervis Arterias Venasŋue comitantibus, apud Haller, Disput. Anatom. Select, tom. iii. ]

Organized in the manner now described, it is requisite to take a short view of the anatomical connections of the arterial system, or to consider it in its origin, its course, and its termination.

The arterial system of the animal body may be viewed as one large trunk divided into several branches, which again are subdivided and ramified to a degree of minuteness which exceeds all calculation. It is requisite, therefore, to consider the origin, Isí, of the aorta, the large trunk; 2dly, of the branches which arise from it; and, 3c?(y, of the small vessels into which these are divided.

Every one knows that the aorta is connected at its origin with the upper and anterior part of the left ventricle. The manner of this connection has been well examined by Lancisi, by Ludwig, and particularly by Bichat. It may be demonstrated by dissection, but is much more distinctly shown by boiling the heart with the blood-vessels attached. In a heart so treated, the thin internal membrane may be traced passing from the interior of the ventricle along the margin of its orifice to the inside of the arterial tube. Exactly at the point of union it is doubled into three semicircular folds, forming semilunar valves, and thence is continued along the whole course of the artery. This membrane is entirely distinct from the proper or fibrous coat. Of the latter, the cardiac extremity or beginning is notched into three semicircular sections, each of which corresponds to the base or attached margin of a semilunar valve. These sections are attached to the aortic orifice of the ventricle by delicate filamentous tissue, but are not connected with the fleshy fibres of the heart; and at the angle or point of attachment the thin inner membrane is folded in so as to fill up a space or interval which is left between the margin of the orifice and the circumference of the proper arterial tissue, where it is notched or trisected.

The aorta is soon divided into branches, which again are subdivided into small vessels. With the mathematical physiologists it was a favourite problem to ascertain the number of branches into which any vessel might be subdivided. Keill made them from forty to fifty. Haller states that, counting the minutest ramifications, he has found scarcely twenty. The inquiry is vain, and cannot be subjected to accurate calculation. In no two subjects is the same artery found to be subdivided the same number of times; and in no two subjects are the same branches found to arise from the same trunk.

A branch issuing from a trunk generally forms with it a particular angle. Most generally, perhaps, these angles are acute; but in particular situations they approach nearly to a right angle. Thus the innominata, left carotid, and left subclavian, issue from the arch of the aorta nearly at a right angle, at least to the tangent of the arch. The intercostals form a right angle with the thoracic aorta; the renal and lumbar arteries form a large acute angle, approaching to right, with the abdominal; and the coeliac comes off nearly in the same manner from the anterior part of the vessel. The internal and external carotids, again, the external and internal iliacs, the branches of the humeral, and those of the femoral, form angles more or less acute with each other. The angle which the spermatics make is, generally speaking, the most acute in the arterial system.

I have already alluded to the structure of the arterial tissue at the divarications. These changes relate both to the inner and to the proper membrane. In the inside of the vessel the inner membrane is folded somewhat so as to form a prominent or elevated point, the disposition of which varies according to the angle of divarication. Is?, When this is rectangular, the prominence of the inner membrane is circular, and is equally distinct all round. 2c?, When the angle is obtuse, as in the mesenteric artery, the prominence is distinct, and resembles a semicircular ridge between the continuation of the trunk and the branch given off, but indistinct on the opposite side where the angle is obtuse. 3c?, If the angle is acute, and that [7:2:719]formed by the branch with the continuation of the trunk is obtuse, the beginning of the artery presents an oblique circle, the elevated half of which is near the heart, the other more remote.

The arrangement of the fibres of the proper tissue is described by Ludwig from the divarication of the iliac arteries, and may be seen in any part of the arterial system where the vessels are large. The circular fibres separating form on each side a half-ring, from which is produced a complete ring, which incloses the smaller rings formed by the circular fibres of the vessel given off. These circular fibres proceed to the prominence of the internal membrane already described, and are arranged round it much in the same manner in which those of the large vessel surround its inner membrane. In this, however, no continuity between the rings of the large vessel and those of the small one can be recognised. The latter are inserted as it were into the former, and they are connected by the continuity of the inner membrane only.

In observing the course or transit of arterial tubes, the principal point deserving notice is the sheltered situation which they generally occupy, their tortuous course, and their mutual communications. In the extremities they are always found towards the interior or least exposed part of the limb, generally deep between muscles, and sometimes lying along bones. When they are minutely subdivided, they enter into the interior of organs, without, however, sinking at once into their intimate substance. In the muscles they are lodged between the fibres; in the brain, in the convolutions; in glands, between their component lobes. In such situations they are generally observed to be more or less tortuous in the course which they follow. On the reasons of this much difference of opinion still prevails. (Bichat and Magendie.)

In the course of the arteries, no circumstance is of greater moment than their mutual communications or inosculations (anastomoses'). Of this there may be two forms, the first when two equal trunks unite, the second when a large vessel unites with a smaller one. Of the first, three varieties have been mentioned. 1st, Two equal trunks may unite at an acute angle to form one vessel. Thus, in the foetus, the ductus arteriosus and the aorta are conjoined; and the two vertebral arteries unite to form the basilar trunk. 2d, Two trunks may communicate by a transverse branch, as the two anterior cerebral arteries do in forming the anterior segment of the circle of Willis. 3d, Two trunks may, by mutual union, form an arch, from the convexity of which the minute vessels arise, as is seen in the branches of the mesenteric arteries. (Plate XXIX. fig. 4.)

The second mode of inosculation is frequent in the extremities, especially round the joints. The multiplied communications of the arterial system in these regions, though well known to anatomists, and enumerated by Haller, were first clearly and systematically explained by Scarpa, and afterwards by Cooper and Hodgson. The importance of this arrangement, in facilitating the motions of the circulation,—in obviating the effects of local impediment in any vessel or set of vessels,—and in enabling the surgeon to tie an arterial trunk when wounded, affected with aneurism or any other disease,—has been clearly established by these authors. Their researches have shown, that there is not a single vessel which may not be tied with full confidence in the powers of the collateral circulation. Even the aorta has in four instances been found obstructed in the human subject, and a ligature has been put on its abdominal portion. (Cooper.)

To ascertain the several modes in which arteries terminate has been a problem of much interest to the physiologist, and of no small difficulty to the anatomist. The alleged terminations, as believed to be established, are minutely and elaborately enumerated by Haller, who, however, multiplied them too much according to the modern acceptation of the term.

1. The first undoubted termination of arteries is immediately in veins. It is unnecessary to adduce in support of this fact the long list of observers enumerated by Haller. It is sufficient to say that it was clearly established by the microscopical observations of Lecuwenhoeck, Cowper, and Baker, by Haller himself, and by Spallanzani in his beautiful experiments on the circulation of the blood.

2. The second termination which may be mentioned here is that into the colourless artery, (arteria non rubra). This is sufficiently well established by the phenomena of injections.

3. A third termination which is supposed to exist, but of which no sensible proofs can be given, is that into colourless vessels supposed to open by minute orifices on various membranous surfaces, and therefore termed exhalants. The nature of these vessels shall be considered afterwards.

Haller admits a termination in, or communication with, lymphatic vessels, but allows that it is highly problematical. Partial communications have been traced between arteries and lymphatics by several anatomists; but the point requires to be again submitted to accurate researches.

Another mode of termination, that namely into excreting ducts, admitted by Haller, scarcely requires particular mention. So far as an artery can be said to terminate in such a manner, it would come under the head of that into exhalant vessels. Many of the proofs mentioned by Haller, however, may be shown to be examples of a morbid state of the mucous membranes of these ducts, in which their capillary vessels are disorganized.

In considering the several terminations of arteries, it is not unimportant to advert to the distribution of these vessels. Injections show that they penetrate into every texture and organ of the animal body, excepting one or two substances in which they have never yet been traced. But in different textures they are found in different degrees; and they may vary in extent even in the same texture in two different conditions. The parts which receive the largest and most numerous vascular ramifications are the brain and spinal chord, the glandular organs, the muscles voluntary and involuntary, the mucous membranes, and the skin. In bones, on the contrary, in the fibrous membranes, and their modifications, tendons, and ligaments, and in the serous membranes, few arteries are seen to penetrate; and these are generally minute, sometimes only colourless capillaries. In some textures arteries cannot be traced, though their properties indicate that they must receive vessels of some kind. Such are cartilage and the arachnoid membrane. (Ruysch and Haller.) Lastly, arteries are not found in the scarf-skin, in nails, the enamel of the teeth, .the hair, nor in the membranes of the umbilical chord. In early life bones are much more vascular than in adult age; and in the bones of young subjects arteries may be traced going out through the epiphyses into the cartilages, in which they cannot at a later period of life be demonstrated. (Phil. Trans. No. 470.)

Vein, Venous Tissue. (φλi∙ψ,— Vena, —Tissu Veneux.)

The structure of the tubular canals, termed veins, has been much less examined by anatomists than that of the arteries. Some incidental observations in the writings of Willis, Glass, and Clifton Wintringham, comprise all that was published regarding them previous to the short ac [7:2:720]count of Haller. Since that time they have been described with various degrees of minuteness and accuracy by John Hunter, Bichat, Magendie, Gordon, Marx,^[21. Diatribe Αnatomicophysiologica de Structura atque Vita Venarum. Caroliruhae, 1819. ] and Meckel. In the following account, the facts collected by these observers have been compared with the appearance and visible organization presented by veins in different parts of the human body.

The veins are membranous tubes extending between the right side or pulmonary division of the heart and the different organs in which their minute branches are ramified.

Every venous tube greater than one line in diameter consists of three kinds of distinct substance. The outermost is a modification of the filamentous tissue (membrana cellulosa), and though less compact and less thick than the arterial filamentous envelope, is in every other respect quite similar, and is in general intimately connected with it. The innermost (membrana intima) is a smooth very thin membrane. Between these is found a tunic somewhat thicker, which is termed the proper venous tissue (tunica propria venae). The structure and aspect of this proper membrane shall be first considered.

l,s√, When the loose filamentous tissue in which the blood-vessels are inclosed, and the more delicate and firm layer immediately contiguous to the veins, are removed, the observer recognises a red or brown-coloured membrane, not thick or strong, but somewhat tough, which is the outer surface of the proper venous tunic. If dissected clean it is tolerably smooth; but however much so it can be made, a glass of moderate powers, or even a good eye, will perceive numerous filaments adhering to it, which appear to be the residue of the cellular envelope.

According to Bichat, parallel longitudinal fibres, forming a very thin layer, may be distinguished in the larger veins; but he admits, although they are quite real, that they are always difficult to be seen at the first glance. In the trunk of the inferior great vein (vena cava inferior), they are always seen, he observes, more distinctly than in that of the superior; and they are always more obvious in the divisions of the former than in those of the latter vessel, and also in the superficial than in the deep-seated veins. These longitudinal fibres, he asserts, are more distinct in the saphena than in the crural vein, which accompanies the artery. Lastly, he remarks, these fibres are proportionally more conspicuous in branches than in trunks. (Anatomie Générale, tom. i. p. 399.)

Notwithstanding the apparent correctness of this description, Magendie informs us he has sought in vain for the fibres of the proper venous membrane; and he remarks that, though he has observed very numerous filaments interlacing in all directions, yet these assume the longitudinal and parallel appearance only when the tube is folded longitudinally,—a disposition often seen in the larger veins.

By Meckel, on the contrary, the accuracy of the observation of Bichat is maintained. This anatomist states that he has, by the most minute dissections, assured himself that these fibres are longitudinal; but he admits that they are not uniformly present in all parts of the venous system, and that in degree and abundance they are liable to great variation. He follows Bichat also in representing these fibres as thicker and more distinct in the system of the inferior than in that of the superior cava, and in the superficial than in the deep veins.

In the inferior cava of the human subject, certainly, filaments or fibres may be recognised. But instead of being longitudinal, they may be made to assume any direction, according to the manner in which the filamentous tissue is removed. For this reason probably these fibres are to be viewed as part of the filamentous sheath. In the saphena vein of the leg oblique fibres may be seen decussating each other; but it is doubtful whether these belong to the proper venous tissue or to the filamentous covering.

The nature of this proper membrane, or venous fibre, as it is sometimes named (Bichat), is not at all known. Its great extensibility, its softness, its want of elasticity in the circular direction, or fragility, its colour and general aspect, distinguish it from the arterial tunic. It possesses some elasticity in the longitudinal direction, and is retracted vigorously when stretched. It possesses considerable resistance, or in common language is tough. The experiments of Clifton Wintringham show that it sustains a considerable weight without breaking, and that this toughness is greater in early life, or in the veins of the young subject, than at a later period.^[22. Experimental Inquiry on tome parts of the Animal Structure. London, 1740. ] In short, it may be stated as a general fact, that venous tissue, though thinner, possesses greater elasticity and tenacity than arterial tissue. According to the experiments of the same inquirer, this property depends on that of the superior density of the venous tissue; the specific gravity of the matter of the vena cava being invariably greater than that of the aorta in the same subject, both in man and in brute animals.

From some experiments Magendie is disposed to consider it of a fibrinous character. But it exhibits in the living body no proof of muscular structure or irritable power. When punctured by a sharp instrument, or exposed to the electric or galvanic action, it undergoes no change or sensible motion.

This tunic is wanting in those divisions of the venous system termed sinuses, in which its place is supplied by portions of the hard membrane (dura meninx). 2dly, The inner surface of any vein which has been laid open and well washed is found to be smooth, highly polished, and of a bluish or blue-white colour. This is the inner or free surface of the inner venous membrane (membrana intima). It is exceedingly thin, much more so than the corresponding arterial membrane, much more distensible and less fragile. It bears a very tight ligature without giving way as the arterial does; but it also sustains considerable weight, which shows that it is tough and resisting. This is the membrane termed by Bichat common membrane of dark or modena blood. According to the views of this anatomist, it forms the inner or free surface, not only of all the venous twigs, branches, and trunks composing this system of vessels, but it is extended from the superior and inferior great veins over the inner surface of the right auricle and ventricle, and thence over that of the pulmonary artery and its divisions; and through this whole tract it is the same in structure and properties.

This doctrine has not yet been controverted. But perhaps it may be doubted, both with regard to the inner arterial membrane, that the inner tunic of the aorta and of the pulmonary veins is quite the same; and in regard to this inner venous membrane, whether that of the veins in general is quite the same with that of the pulmonary artery. The subject demands further research. Meanwhile strong confirmation is found in the interesting remark of Bichat, that the osseous or calcareous depositions which are common in various spots of the inner arterial [7:2:721]membrane, and especially at the mitral and aortic valves, are never found in the inner venous membrane, or at the tricuspid valve, or in the semilunar valves of the pulmonary artery. Have these depositions been found inside the pulmonary veins, and not inside the pulmonary artery? This fact is still wanting to complete even their pathological similarity.

The inner or common venous membrane is, however, the most extensive and the most uniform of all the venous tissues. It is the only one which is found in the substance of organs, and is present where the cellular and proper membranes are wanting. This is the case not only with venous branches and minute canals as they issue from the substance of muscles, bones, and such organs as the liver, kidneys, spleen, &c., but is also very remarkably observed with regard to the venous canals of the brain. I have already noticed the absence of the cellular and proper tissues in these tubes; and I have now to remark, that the cerebral veins consist solely of the inner membrane while in the brain or membranes, and when in the sinuses, of this inner membrane, placed between two folds of the dura mater. When the jugular vein reaches the temporo-occipital sinuosity, it loses its proper membrane, while its common or inner membrane passes into the hollow of the dura mater, called sinus, and thus forms the venous canal. This fact is readily demonstrated by slitting open either the lateral or the superior longitudinal sinus, when a thin delicate membrane, quite distinct from the fibrous appearance of the dura mater, will be found to line the interior of these canals.

The inner surface of many veins presents membranous folds projecting obliquely into the cavity of the vessel. These folds, which, from their mechanical office, have been named valves (valvulae), are parabolic in shape, have two margins, an attached and free,—and two surfaces, a concave turned to the cardiac end of the vein, and a convex turned in the opposite direction. The attached margin is not straight, as may be imagined, but circular, and adheres to the inner surface of the vessel. The free margin resembles in shape an oblong parabola; and the direction of the valve is such, that a force applied to its convex surface would urge it more closely to the vein, whereas a force applied to the concave surface would either obliterate the circular area of the vessel, tear the valve from the vein, or otherwise meet with resistance.

The size of the valves is variable. In some instances they are sufficiently large to fill the canal of the vessel, and in others they are too small to produce this effect. The obliteration of the circular area of the vessel is most perfect when there are two or three at the same point. Bichat ascribed the variable state of this quality to the dilated or contracted condition of the veins at the moment of death. This, however, is denied by Magendie.

In structure these valvular or parabolic folds are said to consist of a doubling, or two-fold layer of the inner membrane; and with this statement no fact of which we are aware is at variance. A hard prominent line, which generally marks the attachment of their fixed margin to the vein, is asserted by Bichat to consist of the proper venous tissue, the fibres of which, he says, alter their direction for this purpose; and when the common or inner membrane reaches this line, it doubles or folds itself to form the valve, which thus consists of two layers of the inner or common membrane. This, however, is denied by Hunter,^[23. Of Veins, p∙ 182. ] who considers them of a tendinous nature, and by Gordon, who made several unsuccessful attempts to split these two layers.^[24. Anatomy, p. 6G, 67∙ ]

Valves are not uniformly present in all veins. They are found, 1⅛√, in the following branches of the superior great vein—the internal jugular, the azygos, the facial veins, those of the arms, &c.; 2d , in the following branches of the inferior great vein—the divisions of the posterior iliac, of the femoral, tibial, internal and external saphena, and in the spermatic veins of the male.

They are wanting in the trunk of the inferior great vein (cava inferior), in the renal, mesenteric, and other abdominal veins, in the portal vein, in the cerebral sinuses, in the veins of the brain and spinal chord, in the veins of the heart, of the womb generally, and of the ovaries, and perhaps in all other veins less than a line in diameter.^[25. Haller, lib. ii. sect. 2. ] In the cerebral sinuses the transverse chords are supposed to supply their place.

In the lungs they were supposed to be wanting, till their presence was established by Mayer of Bonn.

In situation the valves vary considerably. In general they are found in those parts of venous canals at which a small vein opens into a larger. But even from this arrangement there are deviations. The only valve which is definite and invariable in its situation is the Eustachian (valvula Eustachiana, valvula nobilis), which is always placed at the cardiac end or beginning of the inferior cava, where that vessel is attached to the sinus of the right auricle. Shaped in general like a crescent, the attached margin of which is the arch of a large circle, and the free that of a small one, it proceeds from the left extremity of the sinus downwards, forwards, and towards the left side, where it is insensibly lost on the membrane of the auricular septum. At its lower end it generally covers the orifice of the large coronary vein. This membranous production is always larger, more perfect, and more distinct in the foetus and in the infant, than in the adult. In the latter it is almost always reticulated; and sometimes the only vestige of its existence is a thin chord or two representing its anterior margin. I have seen it reticulated even at the age of sixteen or seventeen, and almost destroyed beyond thirty. Haller was much perplexed to account for the use of this membranous fold.^[26. Haller de Valvula F.ustachii. Extat in Disput. Anatomic. Select, tom. ii. p. 189- ] The conjecture of Bichat, that it is connected with some purpose in the foetal circulation, is entitled to regard.

Dr Gordon mentions a third partial substance, which is occasionally found in local patches at various parts of veins. I have never met with this, and believe it to be accidental, or not connected with healthy structure.

Besides the cellular or filamentous envelope, veins receive capillary arteries, to which there are corresponding veins. The arteries rise from the nearest small ramifying arteries; and the corresponding veins do not terminate in the cavity of the vein to which they belong, but pass off from its body, and join some others from different parts; and at last terminate in the common trunk somewhere higher.^[27. Hunter, x. Of Veins, p. 181. ] Nervous branches, or rather filaments, are observed in the pulmonary artery and great veins only. Are they derived from the great sympathetic, as is generally said?

In the veins, as in the arteries, the anatomist recognises two extremities, the cardiac or collected, and the organic or the ramified. Examined physiologically, however, the terms origin and termination are not of the same import as when applied to the arteries. In reference to the veins, they become convertible terms; and it is the [7:2:722]usage even of writers on anatomy to represent the veins as arising where the arteries terminate, and terminating at the organ from which the latter arise. This distinction must be kept in view in the following observations.

The cardiac extremity or termination of the veins is so well known as to render any minute explanation unnecessary.

The organic extremity or origin of the venous system is more obscure and difficult to be understood. It is indeed impossible to trace the origin of the small venous vessels, unless in the manner in which Lecuwenhoeck,^[28. Arcanα Naturoe Détecta: Opera Omnia, tom. ii. p. IGO, 1G8. ] William Cowper,^[29. Philosophical Transactions, No. 280, p. 1179. Cowper saw this communication of arteries and veins not only in cold-blooded animals, as the lizard, tadpole, and fishes, but in the omentum of a young cat and a dog. ] Henry Baker,^[30. On Microscopes, and the discoveries made thereby. London, 1785, 2 vols. 8vo. ] Haller, and Spallanzani,^[31. Experiments on the Circulation of the Ľĩood, by Lazaro Spallanzani; translated by W. Hall. London, 1801. ] did in their observations on the transparent parts of animals in general cold-blooded. From the experiments of these observers, we know that a very small vessel, evidently tending and conveying blood towards a larger, connected with a venous branch, may be seen passing directly from a similar small vessel, as evidently conveying blood from a larger, which is connected with the arterial system. All that we know from this, however, is, that a vein containing red blood may rise from an artery conveying red blood. This is matter of pure observation; and all beyond is little more than conjectural.

Haller, indeed, admits origins of veins as manifold as the terminations of the arterial system, a view in which he has been followed by almost all subsequent authors; and Bichat states it as a leading proposition, that the veins arise from the general capillary system. Neither conclusion is founded on strict observation; and while that of the former physiologist is derived chiefly from uncertain facts and loose analogies, the statement of the latter is too hypothetical and general to be either entirely true or wholly false.

Of one fact only are we certain. The blood which is conveyed into the small vessels and the substance of the tissues and organs is brought back by the veins. We have seen that the only origin which is strictly susceptible of demonstration is that of the red vein from the red artery. The point then to be ascertained is, whether colourless veins and absorbent veins arise from the several textures, as colourless and exhalant arteries terminate in them. The proper place for the further examination of this question is the subsequent section.

I must not omit to mention, nevertheless, that the veins have been shown to be connected at their ramified extremities with the lymphatics.

When the veins become distinct vessels, branches, and trunks, they become once more objects of sensible examination. In their course from their organic to their cardiac extremities they present various circumstances which merit attention.

1. In general every artery is accompanied by a venous tube, which is divided in the same manner, and furnishes or receives an equal number of branches. Thus the descending aorta is accompanied by the vena cava inferior ; the common iliac arteries by common iliac veins; the anterior iliac, femoral, and popliteal, by anterior iliac, femoral and popliteal veins. These veins are deep-seated, and are generally named the concomitant veins (venae comites vel venae satellites). In some situations an artery may be accompanied either in its trunk or in its branches by two veins of equal size. Thus in general the brachial artery, and its branches the radial and ulnar, are each accompanied by two veins. The only situations in which the number of veins can be said to be exactly equal to that of the arteries, are in the stomach, in the intestinal canal, in the spleen, in the kidneys, in the testicles, and in the ovaries.

2. In the extremities and in the external regions of the trunk we find, in addition to the concomitant veins, an external layer of venous tubes immediately beneath the skin, (venae subter cutern dispersae, Pliny). These subcutaneous or superficial veins do not correspond to any artery; but as they are chiefly destined to convey the blood from the skin and other superficial parts, they open into the deep-seated veins. Thus in the case of the basilic and cephalic, two superficial veins of the arm, the former, after passing the bicipital fascia, forms in the sheath the brachial vein; and becoming the axillary in the axilla, receives the latter vessel. In the same manner the saphena (pλ≡-ψ δa^η ∖ ης, vena manifesta), or superficial vein of the leg, passes through the falciform process of the fascia lata to join the femoral vein.

From this it results that the venous canals are on the whole more numerous than the arterial. In a few situations only a single vein corresponds to two arteries, as in the penis, the clitoris, the gall-bladder, and the umbilical chord. Often also in the renal capsules and the kidneys two or more arteries have only one corresponding vein. In such circumstances the vein is always large and capacious.

It has been generally stated that the calibre and area of the venous tubes are much larger than those of the corresponding arteries, and consequently that the capacity of the venous system is much greater than that of the arterial. I acknowledge that I know not on what exact evidence the former of these propositions, the only one with which the anatomist is concerned, is made to rest. If it be mere inspection in the dead subject, or the effects of injection, little doubt can be entertained that the alleged greater calibre depends chiefly on the Iaxity and distensible nature of the venous fibre. The arterial tubes appear small in consequence of annular contraction, or the tendency which they have to collapse, when the distending force has ceased to operate. The venous canals appear large by reason of their distension and distensibility during life, from the tendency to accumulation in their branches in most kinds of death, except that by hemorrhage, and from a smaller degree of the physical property of shrinking and annular contraction when empty.

When a vascular sheath is exposed in the human subject, as in the operation for aneurism, or in the lower animals in the way of experiment, the vein generally appears larger than the corresponding artery. This, however, is never so considerable as it is represented by most authors, and certainly cannot afford grounds for the estimates which Keill, Jurin, and other mathematical physiologists have assigned to the relative capacity of the arteries and veins. It is also to be observed that something of this greater size depends on the increase of dilatation resulting from removing the pressure of incumbent parts. In young animals also the difference between the size of the veins and their corresponding arteries is so trifling as to be scarcely discernible. This shows that [7:2:723]something is to be ascribed to the incessant operation of a dilating force increasing uniformly with the duration of life.

Upon the whole, it is chiefly on the ground of their larger numerical arrangement that the veins collectively can be said to be more capacious than the arteries. On this subject some observations of Bichat are entitled to attention.^[32. Anatomie Générale, tome i. p. 378. ]

3. The veins in general accompany the arteries. The venous trunk placed contiguous to the arterial in the same sheath, is divided into branches at the same points, and is distributed into the substance of organs much in the same manner. From this arrangement, however, certain deviations are observed in particular regions. Thus, in the brain, neither the internal carotid, nor the basilar artery, nor their large branches, are accompanied with veins. The small branches only have corresponding veins, which, as they unite to form large ones, pour their blood into the venous canals termed sinuses, the arrangement of which is unlike any other part of the venous system. In the chest also a different disposition of the venous from the arterial tubes is observed. The venae cavae, though conveying the blood to the pulmonic division of the heart, as the aorta conveys it from it, do not, however, correspond with the latter either in situation or in dependent branches. The azygos and the demiazygos veins, in like manner, which receive the intercostal veins, have no concomitant artery, but open into the superior cava, to which they may be viewed as appendages. Lastly, The portal vein, which is formed of the united trunks of the splenic, superior mesenteric and inferior mesenteric veins, corresponds to no individual arterial trunk, and forms of itself a peculiar arrangement in the venous system.

Some anatomists have dwelt much on the more superficial and less sheltered situation of the veins than of the arteries. On this point no positive inferences can be established. In the extremities the former are in general most superficial; but in the interior of the body, especially in the chest, the venous trunks are quite as deep-seated as the arterial.

The course of the venous canals is in general more rectilineal and less tortuous than that of the arteries. In no part of the venous system is such an inflection presented as that which the internal carotid makes in the carotic canal. The general result of this is, that a set of venous tubes is shorter than a corresponding set of arterial ones. The trunks also are less inflected than the branches.

4. The mutual communications of the venous system (anastomoses, inosculationes,) are more numerous and frequent than those of the arterial. 1. The minute veins communicate so freely as to form a perfect net-work. 2. In the twigs, though more rare, these communications are still frequent. 3. In the branches, though less numerous, they are nevertheless observed; and in this respect alone the venous must be greatly more numerous than the arterial inosculations, which are confined chiefly to the smaller and more remote parts of the system. These inosculations, indeed, between the venous branches constitute one of the most peculiar and important characters of their arrangement, in so far as by their means the communication is maintained between the superficial and deep-seated vessels of the system. Thus the emissary veins are the channel of communication between the cerebral sinuses and the temporal, occipital, and other external veins. The external and internal jugulars communicate by one or two considerable vessels; and the free communication between the basilic and cephalic by the median veins, that between them and the deep brachial vessel, and that between the saphena and its branches and the femoral vein, are sufficiently well known. The application of these anatomical facts to the ready motion of the venous blood is obvious.

But of all the communications between the branches or large vessels of the venous system, the most important, both anatomically and physiologically, is that maintained by means of the vena azygos between the superior and inferior cavae. The azygos itself is connected at its upper or bronchial extremity with the superior cava, and at its lower extremity it is in some subjects connected directly with the inferior cava, in others by means of the right renal vein, and in most by the first lumbar veins. By means of the demiazygos, again, it is connected with the left renal vein, or the lumbars of the same side, and in some instances directly with the inferior cava. To the azygos and demiazygos, therefore, belongs the remarkable property of connecting not only the venous canals of the upper and lower divisions, but those of the right and left halves of the body.

System of Capillary Vessels, — Terminations of Arteries, — Origins of Veins.

Though we can scarcely, with propriety, speak of the capillary tissue, or the tissue of capillary vessels, we find it requisite to introduce in this place the general facts of the anatomical peculiarities of this important part of the human body.

The term capillary system, though much spoken of in physiological and pathological writings, is perhaps not always precisely defined or distinctly understood. According to Bichat, it is not only the common intermediate system between the arteries and veins, but the origin of all the exhalant and excreting vessels.^[33. Ibid. vol. i. p. 471. Système Capillaire, article 1. ] If we consider the modes in which arteries have been said to terminate, and veins to take their origin, we find, that in this view of the capillary system there are some things which are doubtful, and some which are inconsistent with the rest.

Haller, and most of the physiological authorities since his time, concluded, chiefly from the phenomena of injections, sometimes from microscopical observation, and, where these failed, from the obscure and uncertain evidence of analogy, that an artery traced to its last or minute divisions will be found to terminate in one or other of the following modes. 1sZ, Either directly in a red vein or veins; 2d, in excreting ducts, as in the lacrymal and salivary glands, the kidney, liver, and pancreas, the female breast, and the testicle of the male; 3d, in exhalants, as in the skin, in the membranes of cavities (serous membranes), the cavities of the brain, the chambers of the eye, the filamentous tissue, the adipose cells, the pulmonary vesicles, and mucous surfaces and their follicular glands; 4/Ä, in smaller vessels, for instance lymphatics; and, 5th, in the colourless artery (arteria non rubra) ^[34. Elementa Physiologice, lib. i. sect. 1, p∙ 22-29. ]

A similar application of the same facts has assigned to the veins a mode of origin not unlike. If, therefore, we admit the definition given by Bichat, it follows that the capillary system consists, 1st, of minute arteries communicating with veins; 2d , of excreting ducts; 3d, of exhalants; and, 4/ä, of minute arteries or veins containing a colourless portion of the blood. It is obvious, however, that it is absurd to say that the system of capillary vessels at once comprehends and gives origin to the excretorics and exhalants. In other respects the whole of [7:2:724]this theory, for little of it is matter of strict observation, rests on very hypothetical grounds.

Of the different kinds of terminations assigned to arteries, and of origins assigned to veins, one only admits of sensible demonstration.. Arteries, when they have so much diminished as to become capillary, are seen by the microscope, in some instances by the naked eye, to pass directly into corresponding capillary veins, or to end abruptly in some organ or membrane unconnected with any other vessel.^[35. Gordon, p. 5G.. ] It is likewise certain that the microscope shows every capillary vein to arise from a capillary artery; and if there be any other mode of origin, it has not yet been demonstrated.^[36. Ibid, p 2G. ] Only one other circumstance requires to be taken into account •in this inquiry. This is, that the capillary artery and vein may contain either red or colourless blood; for, according to the size of the vessels, and the nature of the organs or tissues in which they are distributed, the blood which flows through them will be coloured or colourless. This view of the communication of minute arteries and veins, which is perfectly consistent with the known facts, affords the only explanation which it is possible to give, of the singular division of the capillary system which Bichat has chosen.

This author considers the capillary system under three general heads: 1st, In organs in which it contains blood only, for instance, in the muscles, the spleen, some parts of the mucous membranes; 2d, in organs in which it contains blood and other fluids, for example, in bone, cellular tissue, serous membrane, part of the fibrous system, the skin, the vascular parietes, glands, &c.; and, 3<⅝ in organs in which it contains no blood, the instances of which are, tendon, cartilage, ligament, hair, &c.

Now, it is of little consequence to say that the tissues of the two last divisions contain other fluids than blood, when we are also told that the phenomena of injections, which prove that their capillaries communicate directly with arteries conveying red blood, the effect of irritating applications mechanical or chemical, and the phenomena of acute or chronic inflammation, show that they may receive and convey red blood. The conclusion of this in common language is, that the capillary arteries and veins •of the second order of tissues do not all contain red blood, but that many of them contain a colourless part of that fluid; and that all the capillary arteries and veins of the third order of tissues convey in the natural state colourless blood only. What then is the precise idea which ought to be formed of the intermediate system which Bichat conceived to exist between the minute arteries and veins, or what have been termed the venous radiculce ?

From the present state of facts it results that nothing more can be admitted to constitute the capillary system than those minute vessels, whether conveying coloured or colourless blood, in which inspection, microscopic observation, and injections show that arterial branches at once terminate, and minute veins (radiculce venosoe) have their origin. It is clear that, physiologically speaking, these vessels can neither be regarded as arteries nor as veins strictly; for the characters on which this distinction is founded are necessarily obliterated in this system of vessels. There is no precise point at which the arterial tissue can be said to terminate, and none at which the venous structure can be said to commence. Here inspection or microscopic observation affords little or no aid; for the vessels are too small to allow their structure to be examined correctly. If, however, we adopt the doctrines of Bichat with regard to the inner arterial and venous tunics forming the ultimate tube of small arteries and small veins, we must conclude that the arterial membrane is lost in the venous, and that the common membrane of red blood is identified with the common membrane of dark or modena blood. This conclusion involves nothing absurd or improbable, and, though not founded on observation, it is more natural than many similar ideas which have been formed on the nature of this system of vessels. It may be added, that it is not at variance with what is observed in these vessels in the living body. It is found that the blood in a minute artery is not of the bright red colour which it possesses in the trunk and large branch from which the minute artery derives its blood, but is gradually acquiring the dark hue which belongs to the blood of the venous branches and trunks.

By some, however, this direct communication of minute arteries and veins is denied. Thus, according to Doellinger, the arteries at their last ramifications are void of proper membranous walls; the blood moves in immediate contact with the solid matter of the body, which is in truth the fundamental or penetrating filamentous tissue; and from this it passes into the venous tubes and lymphatics, which also arise from this substance.

According to Wilbrand, again, who equally denies this direct communication of arteries and veins, all the blood is converted into organic fibres and secretions; and these organic fibres, becoming gradually fluid, are converted into blood and lymph, which continue the circulation.

These notions are too fanciful and too incapable of demonstration to become the object of serious attention to the anatomist. It is of little moment whether the vessels in the ultimate ramifications possess tunics or not. When they cease to possess tunics they cease to be vessels; and to carry observation beyond this point is either impracticable or useless. In other respects the investigation of this point belongs to the subject of the exhalant vessels.

Bichat describes two great capillary systems in the human body: Isř, The general one, or that which consists of the minute terminations of the aortic divisions, and the origins of the superior and inferior great veins; and, 2d , the pulmonary capillary system, or that which consists of the minute terminations of the pulmonary artery, and the origins of the pulmonary veins. It is evident that the manner in which the first of these systems is here represented communicates a very incorrect idea of its true character, and that there is in truth an individual capillary system, not only for every organ, but in some instances for every tissue. The brain possesses an individual capillary system; and that of the membranes is evidently distinct from that belonging to the organ itself. The heart and the kidneys possess each an individual capillary system; and the liver may be said to have two, one formed by the communication of the hepatic artery and veins, and another consisting of the divisions of the portal vein, with the branches of the hepatic hollow vein; (Vena cava hepatica).

The organic properties of the capillary vessels are as little known as their structure. Many physiological and pathological writers, especially experimentalists, have ascribed to them a power which has at different times been called muscular, tonic, irritable, contractile; and have asserted that, because the larger arteries are provided with a fibrous membrane, which they have called muscular, and to which they have ascribed irritability, or the power of contraction when stimulated, their minute or [7:2:725]capillary terminations must have the same property. This conclusion is completely unfounded for two reasons. Isí, I have already shown that the proper arterial tunic is not muscular in structure, and, according to the best experiments, possesses no property of contraction when stimulated. 2d, Although it be admitted that the proper arterial tissue is muscular and irritable, it is quite certain that observation has not hitherto shown that this tunic can be recognised in arteries smaller than a line in diameter; and in the capillaries properly so called, that is, in vessels which partake of the nature of artery and vein, no such structure has yet been observed.

It is not improbable, however, that the capillaries possess certain organic or vital properties; but all that has been taught on this subject is either hypothetical or derived from an insufficient and imperfect collection of facts. It is certain that the blood which moves through them is beyond the direct influence of the action of the heart, and can be affected by this only so far as it keeps the larger vessels constantly distended with a column of blood which cannot retrograde, and must therefore move forward in the only direction left to it. It has been therefore argued that the capillaries must have an inherent power of contraction, by which this motion is favoured. Is it not sufficient to say that they act merely as resisting canals, to prevent their contents from escaping, and to minister to the various tissues and organs those supplies of blood which the several processes of nutrition, secretion, &c. require?

The effects which the application of mechanical irritants, or chemical substances, as alcohol, acids, and alkalies, produced in the experiments of Hunter, Wilson Philip, Thomson, and Hastings, have been supposed to demonstrate the irritable nature of the capillary vessels. The conclusion is illegitimate, in so far as the results of these experiments are open to several sources of fallacy. In some instances these effects are to be ascribed to incipient inflammation, in others to shrivelling of the capillary structure, or crispation by chemical action, in others to actual coagulation of the blood of the capillaries; but none of them prove satisfactorily any peculiar properties in the vessels of which the capillary system is composed.

While the views of Reuss, and the recent experiments of Dutrochet and Wedemeyer, render it probable that the capillaries possess some contractile power, they by no means prove that this is adequate to impel the blood through them, independently of the impulse of the heart. According to the hypothesis of Reuss, the arterial system is in a state of positive, and the venous in that of negative, electricity; and by the operation of this agent the blood is made to move from the former class of vessels through the capillaries into the latter. From the experiments of Dutrochet, again, on the transmission of fluids through organic membranes, that author infers that, by means of the inward and outward impulse, or that property which he denominates Endosmose and Exosmose, the blood flows through the capillaries into the veins. Lastly, Wedemeyer, who further maintains that the impulsive force of the heart is propagated to the capillary system, concludes, from the effects of injecting fluids, both mild and irritative, and from microscopic observation, combined with the effects of mechanical and chemical irritants, that the capillaries possess considerable contractile power, the ope ration of which is under the influence of galvanism, or nervous energy, or both; but that this, instead of promoting, ought to resist the motion of the blood through them.

Erectile Tissue. ( Vasa Erigentia, — Vascula Erectilia,— Tissu Erectile.)

The system of capillary arteries and veins does not present the same arrangement in all situations and in all the tissues of the human body. A peculiar arrangement of these vessels was early recognised by our countryman William Cowper, who states that he demonstrated the direct communication of arterial and venous canals, not only in the lungs, but in the spleen and penis, “in which,” says he, “I have found these communications more open than in other parts.”^[37. Philosophical Transactions, No. 285, p. 138G. ] This fact, however, was long overlooked by subsequent anatomists.

Among the terminations of arteries enumerated by Haller, one which he referred to the head of exhalants was that of a red artery or arteries pouring their blood into the spongy or cellular structure of the cavernous bodies of the nipple, the clitoris, and the penis, that of the wattles of the turkey, and the comb of the cock.^[38. Elementa Physiologice, lib. ii. sect. 1, § 24. ] His detailed examination of those parts shows, that, with a correct knowledge of their anatomical structure, he had not a very distinct conception of the manner in which their vessels are disposed. It was afterwards pbserved, however, by John Hunter, that the spongy structure of the urethra and glans consists of a plexus of veins.

Bichat remarked that the spleen, and the cavernous body of the penis, instead of presenting, as the serous surfaces, a vascular or capillary net-work, in which the blood oscillates in different directions according to the impulse which it receives, exhibit only spongy or lamellar tissues, still little known in their structure, in which the blood appears often to stagnate instead of moving. As this peculiar structure was known in the cavernous body to be the seat of a motion long known by the name of erection, MM. Dupuytren and Richerand distinguished this arrangement of arteries and veins as a peculiar tissue, under the name of erectile, — a distinction which, though partly understood before, has only now been admitted as well founded in the writings of anatomical authors. According to the recent arrangements of Μ. Bedard this tissue comprehends not only the structure of the cavernous body, but that of the spongy substance (corpus spongiosum), which incloses the urethra, and forms its two extremities, the bulb and gland, the clitoris, the nymphae, and the nipple of the female, the structure of the spleen in both sexes, and even that of the lips.^[39. Additions à l’ Anatomie Générale de Xav. Bichat, par P. A. Beclard, p. 118. ]

It is unfortunate that the researches of anatomists on this erectile tissue have been restricted chiefly to the spongy body of the urethra and the cavernous body of the penis; and it is rather by analogy than direct proof that similarity of structure between them and the other parts referred to the same head is maintained. I shall here state what is ascertained.

The cavernous body of the urethra, or what is now termed its spongy body, ^[40. Haller applies the name of cavernous body not only to the structure of the penis, but to that of the urethra. (Elementa Physiologice. lib. xxvii. sect. 1.) ] is represented by Haller to consist of fibres and plates issuing from the inner surface of the containing membrane, and mutually interlacing, so as to form a series of communicating cells,^[41. Ibid. lib. xxvii. sect 1, § 33. ] into which the [7:2:726]proper urethral arteries pour their blood directly during the state of erection.^[42. “Sed et in pene, et in clitoride, et in papilla mammae, et in collo galli indici, nimis manifestum est, verum sanguinem effundi, neque unquam ejus color totus de iis partibus evanescit, quae ab eíî'uso sanguine turgere solent.” (Elementa, lib. xxvii. sect. 3, § 10.) ]

The cavernous body of the penis is in like manner represented to be a part of a spongy nature, or to consist of innumerable sacs or cells separated by plates and fibres, which at the moment of erection are distended with blood poured from the arteries, and which is afterwards removed by some absorbing power of the veins.

This opinion, which was that of many subsequent anatomists, even Bichat himself,^[43. Système Absorbant, sect. 3, p. 598. ] was derived apparently from the facility with which the blood so deposited escapes, not, as it was believed, from divided vessels, but from areolae, or interlaminar spaces. It appears, however, to have been at variance with what had been anciently taught by Vesalius, Ingrassias, and Malpighi, and positively stated regarding these vessels by Hunter; and modern researches have shown it to be completely erroneous. Cuvier and Ribes in France, Maseagni, Paul Farnesc, Moreschi in Italy, and Tiedemann in Germany, have shown that there are no cells or spongiform structure in the erectile tissue of the cavernous body.

The first correct view of the structure of parts of this description in the human subject was given by Maseagni in his account of the arterial and venous communications in the spongy body of the urethra. In 1787 he announced in his work on the Lymphatics, that the parts called cavernous bodies, both in the penis and in the clitoris, are simply fasciculi, or accumulations of arterial and venous vessels without interruption of canal; but that between the arteries and veins of the spongy bodies a dilated cavity or minute cell is interposed. In 1795 repeated minute injections led him to doubt the existence of this sort of cell; and about the close of 1805 he publicly demonstrated the fact, that many veins of considerable calibre, collected in the manner of a plexus, with corresponding arteries, but small and less numerous, really form the outer and inner membranes of the urethra, the whole of the glans penis, and the whole substance of the spongy body. -In each of these parts, and also in the spongy structure inclosing the orifice of the vagina, he ascertained by repeated injections that there are no cells, as was imagined, and that the arteries, reflected as it were, give origin to numerous veins,^[44. "Le arterie vi si ritorcono, e danno origine alie vene, e queste formano in seguito alcuni plessi, i quali accumulati in varia maniera, costituiscono tutto il glande, e tutta quella massa vascolare, che trovasi intorno al canale dell’ uretra, e ali’ ingresso della vagina.” {Prodromo della Grande Anatomia di Paolo Maseagni, capitolo ii. p. Cl. Firenze, 1819, folio.) ] which, forming an intimate plexiform net-work, constitute the whole glans, and the entire vascular body which surrounds the urethra and the entrance of the vagina.

In the cavernous bodies of the penis and clitoris he had not sufficient facts to ascertain the existence of the same structure, as he had never succeeded in injecting these parts so completely as the glans ¶rcA the spongy part of the urethra. Eventually, however, he succeeded, especially in children, in injecting fully these cavernous bodies of the penis and clitoris. He found in their interior nothing but fasciculi of veins, with corresponding arteries, but rather smaller. He inferred, therefore, that these vessels, collected and ramified in various directions, constitute a vascular texture capable of expanding and shrinking, according to the quantity of blood conveyed to it.^[45. Prodromo del Paolo Maseagni, loco citato, p. 61. ]

The general accuracy of this description has been since confirmed by the researches of Paul Farnese and Mores-chi. The latter, especially, has shown, Isř, that the glans consists of arteries and a very great number of minute veins, which pour their blood into the cutaneous dorsal vein; 2d , that the urethra, and especially its posterior part, may in like manner be shown to consist of numerous minute veins, which terminate in a posterior branch of the dorsal vein, and communicate with the veins of the bulbous portion of the urethra; and, 3d, that in the cavernous bodies, though also receiving blood-vessels, these are much less numerous, and are chiefly derived from the urethral vessels.^[46. Commentarium de Urethrae Corporis Glandisque Structura Gto idus Decembris 1810 detecta, Alexandri Moreschii, Eq. Coron. Fer-reae, in Ticinensi primum, tum Bononiensi Archigymnasio Anatomes Professoris. Mediolani, 1817· ]

The same arrangement was recognised by Cuvier in the penis of the elephant, by Tiedemann in that of the horse, by Shaw in the human subject and in the horse,^[47. Medico Chirurg. Trans, vol. x. p. 338, 353. London, 1819. ] and by Mr Houston in the tongue of the chameleon.^[48. Trans, of Royal Irish Academy, 1828. ]

Upon the whole, the facts collected by different anatomists on this subject furnish the following results.

If the arteries, on the one hand, be injected, they are found to terminate in very fine ramifications, the disposition of which is exactly the same as in other parts. If, on the other, the veins be injected, it is easy to perceive the two following circumstances: Ls√, That they are much dilated at their origin, that is, that the venous radiculoe are really more dilated than might be anticipated from the other characters of these vessels; 2d , That the tubular dilatations to which they are accessory form very numerous inosculations or anastomoses, precisely as the capillary system of which they constitute a part. The effect of this arrangement is to give these vessels the appearance of being penetrated with sieve-like openings, resembling areolae, or interlaminar spaces mutually communicating. As the whole difference, therefore, between the capillary vessels of this and other parts of the human frame consists iπ x the minute veins (radiculoe venοsoe) being dilated or distended in a peculiar manner, Bedard concludes that the erectile tissue of the cavernous body consists simply of minute arteries and dilatable veins interwoven in the manner of capillary nets. These distended venous cavities are indeed so remote from being cells, that they are truly continuous with veins, the inner membrane of which may be easily recognised among them.^[49. Additions, p. 119. ]

During erection the blood accumulates in this tissue; but the cause and mechanism of this accumulation are completely unknown.

The spleen, Μ. Bedard thinks, may be said to resemble the cavernous body both in structure and phenomena; and he considers it as at once consisting of erectile tissue, and to be the seat of a species of erection more or less similar to that of the cavernous body. This organ, he argues, becomes the occasional seat of a motion of expansion and contraction; and he adduces the three following conditions in which it takes place. Isŕ, In experiments; when in a living animal the course of the blood in the splenic vein is arrested, the spleen swells, but returns to its former dimensions as soon as the circulation is restored. 2d , In diseases; the paroxysms of intermittent fever are [7:2:727]accompanied with obvious enlargement of this organ, which subsides at the conclusion of the paroxysm. 3d , It appears that the same phenomenon takes place during digestion.

Sir Everard Home, with the assistance of the microscopic inspection of Μ. Bauer, has made many observations on the structure of this organ. But his purpose appears to have been more particularly directed to ascertain the phenomena of its function and uses; and I cannot discover that his ideas on its intimate structure, and the arrangement of its capillary system, are precise or distinct.

The most distinct examples, in short, of erectile tissue are to be found, according to Bedard, in the spongy texture which surrounds the urethra, in the cavernous body of the clitoris, the vascular structure of the nymphae, and in the nipple of the female. The structure of the lips in both sexes is not unlike. The veins of these parts may be shown to be well marked and largely dilated at their origin, so as to give the appearance of cellular net-work. The same disposition is observed in the pulp of the fingers. It has been attempted to explain the motions of the iris by supposing it to be formed of this erectile tissue; but the justice of this conjecture seems doubtful.

In the tissue now described it is manifest that the physiologist ought to place the phenomena of the process distinguished by the name of vital turgescence (turgor vitalis) by Hebenstreit,^[50. Brevis Εχρositio Doctrinae Physiologica: de Turgore Vitali, 1795. Ab Ernesto B. G. Hebenstreit, M.D. &c. Extat in Brera Sylloge Opusculorum, vol. ii. opusc. vi. ] Reil,^[51. Archiv, fur die Physiologic, i. band, 2. heft, S. 172. ] Ackermann,^[52. Ackermann, Physische Darstellung der Lebenscrafl, 1797, i∙ band, s. 11. ] and Schlosser.^[53. Georgii Eduardi Schlosser Dissertatio de Turgore Vitali. Extat in Brera Syiloge, vol. vii. opusc. ii. ] Though these authors suppose vital turgescence in different degrees in almost all the textures of the animal body, their most distinct examples are taken from those parts which consist of erectile vessels. After the explanation of the anatomical structure above given, it is superfluous to seek for any other cause except the arrangement of the minute vessels, and especially that of the veins.

System of Exhalants, Exhalant System. ( Vasa Exhalantia, —Système Exhalant.)

Are there such vessels as the exhalants described by physiological authors? Is their existence proved by observation or inspection? If not, what are the proofs from which their existence has been inferred?

The existence of minute arteries, the open extremities of which are believed to pour out various fluids in different tissues of the human body, has long been a favourite speculation with physiological anatomists. The decreasing vessels (vasculorum continuo decrescentium multi sibique succedentes ordined ^[54. Haller, Elementa, lib. ii. sect. 1, and his notes on Boerhaave, Proelectiones, tom. ii. p. 245. ] ), and exhalant orifices of Boerhaave, must be known to almost all* Haller ascribes to the skin membranes of cavities (serous membranes), ventricles of the brain, the chambers of the eye, the cells of the adipose membrane, the vesicles of the lung, the cavity of the stomach and intestines, an abundant supply of these exhalant arteries or canals, which, according to him, pour out a thin, aqueous, jelly-like fluid, which in disease, or after death, is converted into a watery fluid susceptible of coagulation. The existence of these vessels, he conceives, is established by the watery exudation which appears in these several parts after a good injection of the arteries.^[55. “Aqueum humorem de arteriis perinde exhalare, olei terebinthinae aliorumve pigmentorum, et yivi argenti iter persuadet, quod anatomica manu impulsum, aut omnino vivo in homine a consuetis naturae viribus eo deductum, in ejus humoris, quam vocant, cameram depluit.” (Elementa, lib. vii. sect. 2, § I.) ]

As these minute canals, however, through which this injected fluid is believed to percolate, have never been seen, or rendered capable of actual inspection, their existence was denied by Maseagni, who ascribed the phenomena of exhalation to the presence of inorganic pores in the arterial parietes, through which, he imagined, the fluids transuded to the membranes or organs in which they were found. This mechanism, which was equally invisible with the Hallerian, was, for obvious reasons, denied by Bichat, who resolved to reject every opinion not founded on anatomical observation, and to determine the existence of the exhalants by this evidence alone. Obliged, however, to avow the difficulty of forming a distinct idea of a system of vessels, the extreme tenuity of which prevents them from being seen, he undertook to attain his object by what he terms a rigorous train of reasoning.

This consists in the effects observed to result from successful injections of watery fluids, or of spirit of turpentine containing some finely levigated colouring matter; from the phenomena of active hemorrhage, which Bichat considers merely as exhalation of blood instead of serous fluid; and from numerous considerations unfolded in the further prosecution of the subject. In this manner he concludes, that the only points ascertained are, Isř, the existence of exhalants; 2d , their origin in the capillary system of the part in which they are distributed; and, 3d , their termination on the surfaces of serous and mucous membranes, and the outer surface of the corion or true skin.

The exhalant vessels, the existence, origin, and termination of which he thus proved, he distinguished into three classes. The first contains those exhalants which are concerned in the production of the fluids which are immediately removed from the body,—the cutaneous and the mucous exhalants; the second contains those exhalants which are employed in the formation of fluids which, continuing a given time on various membranous surfaces, are believed to be finally taken again into the circulation by means of absorption; and the third class consists of the exhalants concerned in the process of depositing nutritious matter in the different tissues and organs of the human frame. This arrangement is more distinctly seen in the following table.
[table]

Each organic tissue is in this system supposed to have its appropriate exhalant arteries, from which it derives the material requisite for its nutrition.

The clearness and regularity of this arrangement would render it desirable that the existence of these vessels were demonstrated with certainty. It is evident, however, that the regularity of arrangement is the only advantage which it possesses over the views of those authors whose method and opinions Bichat professed not to follow. The existence of exhalants is as little proved [7:2:728] in the rigorous reasoning of Bichat as in the fanciful theories of Boerhaave, the generalizing conclusions of Haller, or the bold supposition of lateral porosities by Maseagni. This defect in his system has therefore been recognised recently both by Magendie and Bedard, the first of whom, though he admits the existence of exhalation as a process of the living body, allows that no explanation of its mechanism or material cause has been given, and asserts that Bichat has created the system of vessels termed exhalants; while the second thinks that anatomical observation furnishes no evidence of their existence.

The colourless capillaries, he observes, which are admitted by all, and the existence of which is satisfactorily established by the well-known experiment of Blculand, proves nothing whatever concerning the existence of exhalant vessels; for these colourless arteries are observed to terminate in colourless veins, and there is no proof hitherto adduced of their proceeding further, or terminating by open mouths. He admits that the fact of exhalations in the living body, of nutrition, of transudation by arterial extremities, shows that these extremities possess openings through which the fluids of exhalation, the materials of nutrition, and the matter of injection, escape. But whether these openings are found at the point at which the capillary arteries are continuous with veins, or belong to a distinct order of vessels continued beyond these arteries, is a question which observation has not yet determined, and which it perhaps is unable to determine. Such is the present state of knowledge in relation to the existence of exhalant arteries. While the process of exhalation is admitted, we must avow, as Cruikshank did long ago, that we are unable to prove satisfactorily the existence of any set of vessels, or any mechanism by which it might be accomplished.

Lymphatic System. ( Vasa Lymphatica, Vasa Lymphifera, Lymphoe-Ductus of Glisson and Jolyffe,— Système Absorbant,— Die Saugadern

In most situations of the human body, and especially in the vicinity of arterial and venous trunks, there are found long, slender, hollow tubes, pellucid or reddish, which present numerous knots, joints, or swellings in their course, and to which the name of lymphatics or absorbents has been given. It is most expedient to employ the former appellation only, as the latter implies the performance of a function, the reality of which has been much questioned of late years.

Though Eustachius had seen the thoracic duct in the horse, and some slight traces of a knowledge of vascular tubes, different either from arteries or veins, are found in the writings of Nicoaus Massa, Fallopius, and Veslin-gius, the merit of establishing their existence is generally ascribed to Caspar Asellius, a physician of Pavia. This anatomist, who had in 1622 seen the white-coloured tubes, then first named lacteals, issuing from the intestines of the dog, observed also a cluster of vessels less opaque near the portal eminences of the liver,—an observation which he afterwards repeated in the horse and other quadrupeds. The same vessels were also described and delineated by Highmore.

Passing over the uncertain and obscure hints given by Walaeus and Van Horne, the first exact information after Asellius is that which relates to Olaus Rudbeck, who, in 1650, is said to have seen them in a calf, and to have demonstrated the thoracic duct, and the dilated sac, afterwards termed receptaculum chyli.

Glisson informs us that Jolyffe had in 1652 imparted to him the knowledge of a set of vessels different from arteries and veins; and it appears, from the testimony of Wharton, that Jolyffe had demonstrated these vessels in 1650.^[56. Francisci Glissonii Αnatomia Hepatis, cap. xxxi.; Thomae Wharton Adenog raphia, cap. ii. p. 98. ] In short, the discovery of lymphatics, and the correction of some errors of Asellius, are ascribed to the English anatomist, not only by Wharton and Glisson, but by Charleton, Plott, Wotton, and Boyle.

The existence of these vessels, thus partially demonstrated, was afterwards more fully established by the researches of Bartholin, Pecquet, Bilsius, Nuck, the second Monro, and Haller. It is chiefly to the exertions of William Hunter, and his pupils Hewson,^[57. Experimental Inquiries, Part the Second; by William Hewson, F. R. S. London, 1774, 8vo. ] Sheldon,^[58. The History of the Absorbent System, &c. by John Sheldon, surgeon, F. R. S. &c. London, 1784, folio. ] and Cruikshank,^[59. The Anatomy of the Absorbing Vessels of the Human Body, by William Cruikshank. London, 1786, 4to. ] in this country, and to those of Maseagni^[60. Pauli Maseagni Vasorum Lymphaticoum Corporis Humani Historia et Ichnographia. Paris, 1787, folio, capitolo i. ] in Italy, that the anatomical world are indebted for the complete examination and history of this system of vessels.

The lymphatic vessels consist, in the members, of two layers, a superficial and a deep-seated one. The first is situate in the subcutaneous cellular tissue, between the skin and the aponeurotic sheaths, and accompanies the subcutaneous veins, or creeps in the intervals between them. A successful injection of these superficial lymphatics will show an extensive net-work of mercurial tubes surrounding the whole limb.

The deep-seated layer of lymphatics is found chiefly in the intervals between the muscles, and along the course of the arterial and venous trunks. In tracing both layers of lymphatics to the upper, fixed, or attached end of the members, we find they increase in volume and diminish in number. At the connection of the members with the trunk, they are observed to pass through certain spheroidal or spherical bodies, termed lymphatic glands or ganglions. The lymphatics of the upper extremity, after passing through the glands of the armpit, terminate in trunks, which open into the subclavio-jugular veins, one on each side of the neck. Those of the lower extremity, after passing through the glands of the groin, proceed with the common iliac vein into the abdomen, where they unite with other lymphatics.

The lymphatics of the trunk consist in like manner of two layers, a subcutaneous and deeper seated one, distributed in the chest between the muscles and pleura, and in the abdomen between the muscles and peritoneum. In the chest and belly, each organ possesses a superficial layer of lymphatics distributed over its surface, and pertaining to its membranous envelope; the other ramifying through its surface, and pertaining to the peculiar tissue of the organ. This twofold arrangement is most easily seen in the lungs, the heart, the liver, spleen, and kidneys.

In a similar manner are arranged the lymphatics in the external parts of the scull; on the face, where they are very numerous; in the spaces between the muscles; and on the neck, in which they pass through numerous glands. No lymphatics, however, have been found in the brain, the spinal chord, their membranous envelopes, the eye, or the ear.
[7:2:729]

All the lymphatics hitherto known terminate in two principal trunks. One of these, termed from its site thoracic duct (ductus thoracicus, die Milchbruströhre, Ze canal thoracique), is situate on the left side of the dorsal vertebrae. It receives the lymphatics of the lower extremities, of the belly, and the parts contained in it; those of great part of the chest, and those of the left side of the head, neck, and trunk, and left upper extremity. The other lymphatic trunk, which is situate on the right side of the upper dorsal vertebrae, is formed by the union of the lymphatics of the right side of the head, neck, right upper extremity, and some of those of the chest. Both of these trunks open into the subclavio-jugular vein of each side.,

That lymphatics terminate in branches of the venous system, has been asserted on the authority of various observers. Steno, for instance, states that he traced the lymphatics from the right side of the head, the chest, and pectoral extremity, in animals, into the right axillary vein; and he gives delineations of anastomotic connections of several lymphatics with the axillary and jugular veins. Similar facts have been reported by Nuck, Richard Hale, Bartholin, and Hartmann. Ruysch traced the lymphatics of the lung into the subclavian and axillary veins; Dre-lincourt those of the thymus gland in animals into the subclavians; and Hebenstreit saw those of the loins pass into the vena azygos.

Haller, though unwilling to deny the testimony of these observers, considers it liable to various sources of fallacy, and doubts the direct communication of the lymphatic and venous systems. By John F. Meckel the grandfather, nevertheless, this communication was maintained, from the circumstance that he found mercury injected into the lymphatics pass into the veins without any traces of extravasation. From injecting the lymphatics also he found the inferior cava full of mercury, not a particle of which had passed by the thoracic duct into the superior cava. Injecting afterwards an indurated lumbar gland from a pelvic lymphatic, when he found its lower half only was filled, he increased the pressure, with the view of filling the minute vessels of the gland. When this was continued a little, he observed the fluid metal pass into the inferior cava, and thus traced the minute lymphatics into the venous system.^[61. Nova Experimenta et Observationes de finibus Venarum ac Vasorum Lymphaticoum, sect. 1, p∙ 4. Lugd. Bat. 1772.. ]

These facts have received too little attention, from the circumstance that Hewson, though not doubting them as stated by the author, regarded them as liable to considerable fallacy, and, along with William Hunter, imputed the effect in question entirely to extravasation. Both Hunterand Hewson, indeed, appear to have injected veins from lymphatics in the same manner in which Meckel did; but both saw reason to infer that extravasation had taken place. Cruikshank, again, states that he never saw a lymphatic vessel inserted into any other red veins than the subclavians and jugulars. The termination remarked by Steno and his successors constitutes in truth the common trunk or lymphatic vein admitted by Cruikshank,—a thoracic duct of the right side.

Recently this mode of termination has been revived by Tiedemann and Fohmann,^[62. Anatomische Untersuchungen uber die Verbindung der Saugadern mit den Venen. Heidelberg, 1821. ] who state that, in the seal, the lactiferous vessels communicate with veins arising from the mesenteric glands, and pass thence into the venous trunks without proceeding through the thoracic duct. Μ. Lau th junior, of Strasburg, again, conceives that he has demonstrated that lymphatics communicate with veins within the substance of organs, and in the interior of the lymphatic glands ,^[63. Essai sur les Vaisseaux Lymphatiques. Strasbourg, 1824. ] an inference which at present requires further verification. The statements of Lippi of Florence,^[64. Illustrazioni Fisiologiche e Patologiche del Sistema LinfaticoChilifero mediante la scoperta di un gran numero di communicazioni di esso col venoso del Professore Regolo Lippi. Firenze, 1825. ] that every lymphatic almost communicates freely with venous tubes, is still more improbable, and has been rendered exceedingly doubtful by the recent researches of Rossi.^[65. Cenni sulla communicazione dei vasi linfatici colle vene, di Giovanni Rossi, Doctore, &c.: Annali Universali di Medicina, anno 1826, vol. xxxvii. p. 52. ]

The connections of the ends of lymphatics with the organs and tissues from which they arise, termed their origins, are completely unknown. In some favourable instances the lymphatics of the intestinal canal are so filled with a reddish or whitish fluid after the process of digestion has continued for some time, that not only are their larger branches easily seen, but by the aid of the microscope some of the smaller may be traced to their commencement. This, which was ascertained by Crûikshank (p. 55 and 58), and confirmed by Hewson, Blculand, and Hedwig, has been contradicted by the observations of Rudolphi and Albert Meckel. In all other parts, however, though a successful injection may show the course and distribution of many of the smallest lymphatics, yet no orifices are perceptible at the point at which they seem to stop, and we are uncertain whether these points are their origins. (Cruikshank.) Mere observation is here as unavailing as in regard to the termination of exhalants. The continuation of lymphatics with arteries, unless in the case of those which arise from the interior of arterial tubes (Lauth), is not satisfactorily established. It has been conjectured, however, that their ends or imperceptible origins are connected to the tissues to which they are traced, and that the lymphatics arise in this manner from these tissues.

The lymphatics are distinguished by being in general cylindrical in figure, and by varying in calibre at short spaces. In this respect they differ from the arteries and veins. It has been further justly remarked by Gordon, that the middle-sized lymphatics are remarkably distinguished from the corresponding parts of the arterial and venous system by three peculiarities: Hi, When two lymphatics unite to form a third, the trunk thus formed is seldom or never larger than either of them separately; 2dly, their anastomoses with each other are continual; and, 3rfZy, they seldom go a great space without first dividing into branches, and then reuniting into trunks.

The outer surface of a lymphatic is filamentous and rough, the inner smooth and polished, like that of small veins. It is impossible to observe the structure of these tubes in the middle-sized, or even in the large lymphatics; and anatomists have generalΓy been satisfied with supposing that the structure of all of them is similar to that of the thoracic duct, or some other large vessels equally susceptible of examination. According to the observations of Cruikshank (chap, xii.), which have been verified by Bichat, the thoracic duct presents, Isí, a layer of dense, firm, filamentous or cellular tissue, exactly similar to that found inclosing arterial and venous tubes, which the latter regards as foreign to the vessel, but giving it a great degree of support and protection; 2dly, a proper membrane, delicate, transparent, and moistened inside by an unctuous fluid, which he seems inclined to [7:2:730]ascribe to transudation. Muscular fibres, of which Sheldon speaks positively, Cruikshank represents, though seen in some instances (chap, xii.), yet to be more generally not demonstrable. Their existence, though admitted by Schreger and Soemmering, is denied by Maseagni, Rudolphi, and J. F. Meckel, and, I may add, by Bichat and Bedard. This account differs not much from that of Dr Gordon, who could not recognise distinctly more than one coat, similar to the inner coat of veins. The filamentous layer noticed by Bichat, and considered by Maseagni as an external coat, is of course excluded.

The knotted or jointed appearance of lymphatics is occasioned chiefly by short membranous folds in their cavity, called valves. These folds are thinner than the venous valves; but they are equally strong, and have the same shape and mode of attachment to the inside of the vessel. They are generally found in pairs, but never three at the same point. A single valve is sometimes found at the junction of a large branch with a trunk, or of a trunk with a vein. According to Cruikshank, there is considerable variety in the distribution of valves; but in general a pair of valves will be found at every one-twentieth of an inch in lymphatics of middling size. In the larger Jymphatics they are less numerous than in the small. The structure of these valvular folds is as little known as that of the inner membrane, of which they appear to be prolongations. According to Maseagni, they sometimes contain a small portion of fine adipose substance.

The tissue which forms the lymphatic tubes is strong, dense, and resisting; and from the weight of mercury which they bear without rupture, it has been generally concluded that they are stronger in proportion to their size than veins. This tissue also possesses considerable elasticity.

The opposite states of lymphatics during digestion and after long fasting, and the phenomena of mercurial injections, prove that the tissue of which they consist is distensible and contractile. Though it does not exhibit appearances of muscular structure, it has been long supposed to be endowed with a property analogous to irritability. Such is the inference which Hunter, Hewson, Cruikshank, and others, have derived from various phenomena in the living and recently dead tissue.

Though Bichat doubts what he terms organic sensible contractility, yet he admits insensible contractility as necessary to the functions ascribed to lymphatics. Previous to his time Schreger, in different experiments, observed the first of these qualities, in consequence of the application not only of acids, butter of antimony, and alcohol, but even of hot water and cold air. Similar contractions and relaxations have been induced by mechanical irritation. Such phenomena are observed not only during life, but even after death; and if to this we add, that the thoracic duct is often after death large and flaccid, though empty, but in the living body is almost always contracted and scarcely visible, and that a portion of it included between two ligatures, and punctured, quickly expels its contents, it may be inferred that the lymphatic tissue possesses a considerable degree of this organic property.

Lymphatic Gland or Ganglion, Kernel. ( Glanduloe Lymphatica, — Glanduloe Conglobatoe, — Die Saugader-Ďru-sen.)

This is the proper place to consider the structure of those bodies which are in common language termed hernels, to which anatomists have applied the name of lymphatic glands, and the French anatomists have more recently given that of lymphatic ganglions. The usual appearance, figure, and situation of these bodies are well known. In general they are spheroidal, seldom quite globular, and most commonly their shape is that of a flattened spheroid. In different subjects, and in subjects at different ages, they vary from two or three lines to an inch in diameter. The medium rate is about half an inch. Their surface is smooth; their colour grayish-pink, sometimes pale red, bluish, or of a peach-blossom tinge,—varieties which seem to depend on degrees of bloody transudation; for, when washed and slightly macerated, they assume the gray or whitish-blue colour. In a few instances they are jet black,—a peculiarity which seems to depend on a degree of black infiltration, or on the incipient stage of that change which has been termed melanosis, or melanotic deposition. The idea that it may be derived from the carbonaceous matter suspended in the atmosphere of great cities, has been shown by Cruikshank to be absurd. Its anatomical possibility may be justly questioned.

They are always situate in the celluloso-adipose tissue found in the flexures of the joints. They are found in small number at the bend of the ham, and that of the elbow; in the armpit and groin they are more numerous; in considerable number in the cellular tissue of the lumbar region, before the psoas and iliacus muscles; and they are most abundant round the neck. The posterior mediastinum, and the cellular tissue between the mesentery and vertebral column, abound with lymphatic glands mutually connected in clusters.

Each gland may be said to consist of a peculiar substance, inclosed in a thin membrane like a capsule. The capsule is a thin, pellucid, colourless substance, which is resolved by maceration into fine whitish fibres. It is very vascular; and Maseagni appears to have detected absorbents in it. It is connected to the proper substance by fine filamentous or cellular tissue. The capsule is considered by Bedard as a fibro-cellular membrane. The proper substance of lymphatic glands consists of a homogeneous pulp, in which injections have shown numerous ramifications of minute vessels. As these vessels are injected from the lymphatics which are seen to enter the body of the gland, they are believed to be continuous with them, and to be lymphatics arranged in a peculiar manner. These vessels are of two kinds, one entering the gland, called vasa afferentia or inferentia, entrant lymphatics; the other quitting, are called vasa efferentia, egredient lymphatics. This distinction is founded on the direction of the valves. In the vasa inferentia the free margins of the valves are turned towards the gland; in the vasa efferentia they are turned from it.

The number of entrant lymphatics varies from one to thirty, and, what is more remarkable, very rarely corresponds with that of the cgredient lymphatics, which are in general much fewer. Cruikshank states that he has injected fourteen entrant lymphatics to one gland, to which only one egredient vessel corresponded. When the entrant lymphatic reaches the gland, it splits into many radiated branches, which immediately sink into its substance. The egredient lymphatics are generally larger than the entrants.

The arrangement of these vessels in the interior of the glands is best described by Maseagni, whose observations are confirmed by Gordon. To see this well, it is requisite to inject the entrant lymphatics of two glands in two different modes; one with mercury, the other with wax, glue, or gypsum. After a successful mercurial injection, the entrants are seen, before sinking in the gland, to divide into two orders of branches. One of them, which belongs chiefly to the surface or circumference of the gland, consists of large vessels, bent, convoluted, and in [7:2:731]terwoven in every direction, communicating with each other, and swelling out into dilated cells at certain parts; and of smaller vessels, which form a minute net-work on the surface, and which seem to terminate in the cells or distended parts of the larger vessels.

From these distended parts or cells, again, arise many minute vessels, which, after winding about on the surface of the gland, unite gradually, and form the egredient vessels of the gland.

The wax, glue, or gypsum injection is employed to show the deep-seated or central vessels of the gland. The distribution of these is found to be quite the same as that of the superficial vessels.

The cells delineated by Cruikshank I am disposed to regard as mere dilated parts of the lymphatic vessels which constitute the intimate structure of the gland.

These minute tubes are connected by delicate filamentous tissue, which is more abundant in early life than afterwards.

Injections show the existence of blood-vessels which accompany the convolutions of the lymphatics in the glands; but no nerves have been found either in the glands or their capsules.

The white matter described by Haller and Bichat is not contained in the cellular substance, but in the cells of the lymphatic vessels themselves.

The three orders of tubes or canals, the anatomical characters of which have now been completed, constitute what has been termed the Vascular System; (Vasa; Systema Vasorum ; Das Gefass System; Le Systeme Vasculaire.) The great extent of its distribution, and the part which it performs in all the processes of the living body, both in health and during disease, must be easily understood. In every texture and organ arteries and veins are found; and in all, except a few, the art of the anatomist has demonstrated those colourless valvular tubes denominated lymphatics. The arrangement of the former, especially in the substance of the several textures, essentially constitutes what is termed the organization of these textures. Many anatomists have imagined that each texture has a proper matter, or parenchyma, by which it was supposed to be particularly distinguished, and which was conceived to consist of minute, inorganic, solid atoms. Whether this opinion be well founded or not, it is perhaps of little moment to inquire. At present it is certain that it is not susceptible of demonstration.

The phenomena of injections, in which he . was eminently successful, led Ruysch to entertain the opinion, that every substance of the animal frame consists of nothing but vessels. This idea, though opposed by Albinus,^[66. Annotationum Academicarum lib. iii. ] on the same grounds on which it was advanced, was nevertheless revived by William Hunter, who believed that the inorganic parts of animal bodies are too minute for sensible, or even microscopical examination. In every part, however minute, always excepting nails, hair, tooth enamel, &c. vessels may be traced; and even a cicatrix, he demonstrated, is vascular to its centre.^[67. Medical Observations and Inquiries, vol. ii. ]

By the aid of the microscope the researches of Lieberkuhn tended still more powerfully to favour this opinion.^[68. De Villis Intestinorum. ] But repeated observation of the effects of injection in every part and texture almost of the body, by Barth and Prochaska, has led the latter to conclude that this opinion, understood in the ordinary mode, is not tenable. Pro-chaska, who has investigated this subject with much attention, thinks he is justified in dividing all the substances of the animal frame into two,—those which may be injected, and those which cannot. In this manner he regards skin, especially its outer surface, muscle, various parts of the mucous membranes, the ρia mater, the lungs, the muscular part of the heart, the spleen, the liver, kidneys, and other glands, as very injectible; but tendon, ligament, cartilage, &c. as not injectible.^[69. Georgii Prochaska Disquisitio AnatomicoPhysiologica Organismi Corporis Humani ejusque Processus Vitalis. Viennae, 1812, 4to. ] Without entering minutely into the merits of this distinction, or the inferences which Prochaska deduces from it, it is sufficient, so far as all useful knowledge is concerned, to infer that blood-vessels are an essential constituent of every organic texture, however different; and if there be any other matter inherent in such textures, it must be derived from these as a secretion. Nerve, brain, muscle, osseous matter, and cartilage, are depositions or the product of nutritious secretion from the respective arteries of these organized substances.

Nerve, Nervous Tissue. (N≡υgoι>,— Nervus, —Tissu Nerveux,— Systeme Nerveux.)

I am unwilling to adopt here the denomination of nervous system, because it is not my intention, under this head, to treat of the brain and spinal chord. I deviate from this practice, Is?, because I do not conceive it demonstrated that the brain is the same organic substance as the nerves; 2c?, because, although it were, this would not contribute to the knowledge of the minute structure of the nervous chords; 3cZ, because the arrangement or these chords in the animal body is inconsistent with this, and will be best understood when described separately.

The nervous system of the animal body includes two general divisions. The first of these, named brain and spinal chord, is collected in a single and indivisible mass, and contained in a peculiar cavity, formed by part of the osseous system of the animal,—the vertebral column, and cranium, in the vertebrated animals generally. The second division of the nervous system, with which alone we are at present concerned, is found in the form of long chords or threads mutually connected, and running in various directions through the body in the mode of ramification. To these the name of nervous trunks or chords, or simply nerves, has been long applied.

The structure of the nerves has been examined with different degrees of accuracy and minuteness by a great number of anatomists. The more ancient authors, who wrote at a period when observation was much corrupted by fancy, and most of those who give descriptions in general systems, may be without much injustice passed over in silence. It is sufficient to say that some good facts are given in the works of Willis, Vieussens, Morgagni, and Mayer; that Prochaska, Pfeffinger, the second Monro, and Fontana, are the first who professedly wrote on the structure of the nerves; that the works of Reil,^[70. J. C. Reil, Exercitationes Anatomica dc Structura Nervorum. Halce, 1797· ] δ Bichat, and Gordon, contain the most accurate information on the nervous,chords in general; and that the treatises of Scarpa^[71. Anatomicarum Annotationum Uber primus de Nervorum Gangliis et Plexibus. Auctore Antonio Scarpa. Ticini, 1792. ] and Wutzer^[72. De Corporis Humani Gangliorum Fabrica atque Usu Monographia. Auctore Carolo Gulielmo Wutzer, Med. Chirurg. Doct. &c. Bcrolini, 1817· ]
[7:2:732]

contain the best descriptions of the arrangement of those parts named ganglions and plexuses.

Each nerve forms connections in three different ways. Isŕ, A nerve must be connected to some part of the central mass by one of its extremities,—the cerebral or spinal end; 2d , it must be connected to some texture or organ, or part of an organ, by the other extremity,—the organic end; and, 3d, it may be connected to other nerves by a species of junction called anastomosis (ansa), anastomosing or uniting point. By means of the first two connections, it is supposed to maintain a communication between the central mass and the several organs; and by the latter it is understood to be subservient to a more general and extensive intercourse, which is believed to be necessary in various functions and actions of the animal system.

Every nerve consists essentially of two parts; one exterior, protecting, and containing; the other interior, contained, and dynamic,^[73. The term dynamic is used to denote in a general sense the properties of animal substances. ] forming the indispensable part of the nervous structure.

The first of these, which has been known since the time at least of Reil by the name neurilema (vευgov e∕λεω, e∕λt}μα, nervi involucrum), or nerve-coat (Nervenhaut, Re'ú; Nervenhiille, MeckeD, has the form and nature of a dense membrane, not quite transparent, which is found on the outside of the nervous chord or filament, and invests the proper nervous substance. It must not, however, be imagined that the neurilema forms a cylindrical tube, in the interior of which the nervous matter is contained. This latter disposition, if it actually exists, applies to the smaller nerves only, and to some of those which go to the organs of sensation,—a peculiarity which we shall notice subsequently.

Any large nervous trunk, for example the spiral or median of the arm, or the sciatic nerve of the thigh, is found to be composed of several small nervous chords placed in juxtaposition, and each of which, consisting of appropriate neurilema and nervous substance, is connected to the other by delicate filamentous tissue. These, however, do not through their entire course maintain the parallel disposition in respect to each other, but are observed to cross and penetrate each other, so as to form an intimate interlacement of nervous chords and filaments, each of which, however minute, is accompanied with its investing neurilema. The neurilema, in short, may be represented as a cylindrical membranous tube, giving from its inner surface many productions forming smaller tubes (canaliculi ; die Nervenröhre; primitive cylinders of Fontana^[74. Observations sur la Structure des Nerfs, &c. apud Traité sur le Venin, &c. par Μ. Felix Fontana. Florence, 1781· ]), in which the proper nervous matter is contained.

Of this arrangement the consequence is, that each nerve or nervous trunk, enveloped in its general neurilema, is composed, nevertheless, of a number, more or less considerable, of smaller chord-like nervous threads (funiculi nervei, Prochaska; chordae, funes, Nervenstrange, ReiD, into which the nerve, by maceration and suitable preparation, may be resolved. Each chord, again, or nervestring, as Reil terms it, though invested with a proper neurilem, may be further resolved into an infinite number of minute filiform or capillary filaments (fila, fibrilloe, Nervenfasern, ReiD, which, invested in a delicate covering, are understood to constitute the ultimate texture of the nerve.

This threefold division may be easily observed in the brachial and spiral nerves of the arm, and still more distinctly in the sciatic in the thigh. The utility of understanding the internal arrangement from which it results will appear forthwith, when the structure of those parts termed ganglions and plexuses comes under examination.

Of this arrangement in different nerves, and in different regions, this membrane undergoes great modification; and all opinions on its nature derived from thickness or transparency are liable to considerable fallacy. Scarpa seems to view it as connected, in anatomical origin and character, with the hard membrane (meninx dura, dura mater). Reil, who devoted more care and time to the examination of its nature and structure than any other inquirer, represents it as consisting of cellular substance, many bloodvessels, and some lymphatics.^[75. Reil, Exercitationes Anatomicae déstructura Nervorum, cap. i. p. 3. ] Bichat thinks it resembles the soft membrane of the brain (pia meninx, pia mater), and is derived from it.^[76. Anatomie Générale, p. 137, &c. ] Gordon considers the neurilema of the cerebral nerves as consisting of soft membrane (pia mater) at their origin, but in all other situations as a species of cellular membrane.

By Mayer the neurilema is accounted a fibrous tissue, for the following reasons. Isŕ, It consists almost entirely of tendinous fibres, and is cellular only where it is very thin. 2d , The transverse folds presented by most, of the nerves, and which give them a denticulated form, are derived from the neurilema, are of fibrous character, and are similar to those observed in tendinous sheaths. 3d , Several nervous productions are actually converted into tendinous or fibrous filaments; for example, the brain of the snail tribe, and the spinal chord both in these and other animals at the cauda equina. 4th, The neurilema is either a continuation of the proper cerebral membrane (pia mater), or very similar to it; and this membrane is fibrous and aponeurotic at the spinal chord, and even at its upper end, and, according to Mayer, forms the denticulated ligament, which is a fibrous tissue.

These views, which are the result, not of observation, but of hypothesis, it is impossible to adopt. Its connection with the pia mater was disproved by Reil; and though its analogy with the denticulated ligament were established, it would prove nothing regarding the neurilema. Upon the whole, the idea of Reil is the most probable. According to the observations of this anatomist, who examined the neurilema after fine and successful injection, it is liberally supplied with blood-vessels. These proceeding from the neighbouring arteries penetrate the filamentous sheath of the nerve; and, immediately on reaching the neurilema, divaricating at right angles, generally run along the nervous threads (funes), parallel to them, forming numerous anastomotic communications, and divide into innumerable minute vessels, which penetrate between them into the minute neurilematic canals. So manifold is the ramification, and so minute the distribution, that in these canals not a particle of nervous substance is found which is not supplied with a vessel.^[77. De Structura Nervorum, cap. v. p. 19. ] The arrangement of the veins is analogous.

It appears, therefore, that the neurilema is a tissue of membranous form, with a multiplied mechanical surface, liberally supplied with blood-vessels, from which the nervous matter is secreted and nourished. It is impossible, indeed, to doubt that, of the two parts which compose the nervous chord, it is the most perfectly organize[7:2:733]; and that, though it may not be similar in structure to the pia mater, it is quite analogous in the use to which it is subservient. Like that membrane, it sustains the vessels of the nerve; it presents a multiplied surface, over which the vessels are distributed; and, by penetrating deep into the body of the nerve, it conveys the nutritious vessels in the most capillary form to the inmost recesses of the nervous substance.^[78. Reil, Exercitationes Anatomieoe de Structura Nervorum, cap. i. ]

The arrangement which has been above described is the only one which can be regarded as general. It varies in particular regions; and these varieties in the neurilematic disposition occur principally in the nerves which are distributed to the proper organs of sensation.^[79. By the term“proper organs of sensation” are understood those of sight, hearing, smell, and taste, which are confined to a fixed spot in the system. ] Isŕ, The olfactory nerve is soft, pulpy, and destitute of neurilema, from its origin in the Sylvian fissure, to the gray bulbous enlargement which terminates its passage in the cranium; but as soon as it reaches the canaliculi or grooves of the ethmoid bone, and begins to be distributed through the nasal anfractuosities, it is distinctly neurilematic. 2d , The optic nerve is still more peculiar in this respect. The instant it quits the optic commissure (commissura tractuum), it begins to be invested by a firm general neurilema, which sends into the interior substance of the nerve various membranous septa or partitions, forming separate canals, in which the nervous matter is contained. These partitions, however, are so thin, that at first sight the optic nerve seems to consist merely of one. exterior membranous cylinder inclosing the proper membranous substance. 3d , Lastly, we may remark, that the auditory nerve, or the soft portion of the seventh pair of most anatomical writers, is the only nerve in which this covering cannot be traced.

The neurilema is much thinner and more delicate in the nerves which are distributed to the internal organs, as the lungs, heart, stomach, &c. (nerves of the organic life, great sympathetic and pneumogastric nerves, par vagum), than in those belonging to the muscular system.

The second component part of the nervous chord or filament is the proper nervous matter which occupies the cavity of the neurilematic canals. Little is known concerning the nature or organization of this substance. It is whitish, somewhat soft, and pulpy; but whether it consists of aggregated globules, as was attempted to be established by Della Torre and Sir Everard Home, or of linear tracts disposed in a situation parallel to each other, as appears to be the result of the inquiries of Monro, Reil, and others, or of capillary cylinders containing a transparent gelatinous fluid, as Fontana represents, seems quite uncertain. It has been presumed, rather than demonstrated, that it resembles cerebral substance. But this analogy, though admitted, would throw little light on the subject; for at present it is almost impossible to find two anatomical observers who have the same views of the intimate nature of cerebral substance itself. Whatever be its intimate arrangement, it appears to be a secretion from the neurilematic vessels. (Reil.)

The structure of the nervous chord may be demonstrated in the following manner. When a portion of nerve is placed in an alkaline solution, the whole, or nearly the whole, of the nervous matter is softened and dissolved, or may be washed out of the neurilematic canals, which are not affected by this agent, and the disposition of which may be then examined and demonstrated.^[80. Reil de Structura Nervorum, cap. i. p. 3 and 5. ] Aqueous maceration may likewise be advantageously employed to unfold this structure; for it separates and decomposes the cellular tissue by which the neurilematic canals are united, and subsequently occasions decomposir tion of the nervous substance, while it leaves, at least for some time, the neurilema not much affected. When, however, the maceration is too long continued, it is separated and detached like other macerated textures.

Lastly, If a large nerve be placed in diluted acid for the space of one or two weeks, the neurilema is gradually dissolved, and the nervous matter becomes so much indurated and consolidated that it may be separated from the contiguous chords in filaments with great facility.^[81. According to the experiments of Reil, nitrous acid diluted with water answers best. Muriatic acid, though equal or even superior in effecting solution of the neurilema, softens the nervous matter too much, and separates the component filaments too completely. (öe Structura Nervorum, cap. iii. p. 16.) ] In undergoing this change, the portion of nerve becomes much shorter and considerably contracted,—is subjected, in short, to the process of crispation; so that unless a large nerve like the sciatic be employed for the experiment, it may be impossible to obtain the result in the most satisfactory form. These experiments, with many others of the same nature, were first performed by Professor Reil, and afterwards repeated and varied by Bichat and Gordon. Personal repetition of them enables me to assert, that, when correctly conducted, they never failed to give the results as described by these authors.

Nervous tissue, like all others, receives a proportion of what may be denominated the systems of distribution,— cellular tissue and blood-vessels. In the substance of the former, the disposition of which we have already remarked, we find the more conspicuous branches of the latter distributed. In a more minute and divided form they penetrate the neurilema and nervous substance. Reil, who derived his conclusions from the result of delicate and successful injections, perhaps over-rated the quantity of blood which in the sound state they convey; for it is quite certain that, in the healthy state, hardly any red blood enters the nervous tissue, as may be easily shown by exposing the sciatic nerve of a dog or rabbit.

No good chemical analysis of nervous matter has yet been published. Every chemical examination of it has been conducted on the assumption that it is analogous to cerebral matter. Of this, however, there is no direct proof. In the analysis by Vauquelin, the neurilematic covering appears not to have been detached,—a proceeding always necessary to obtain correct results in this inquiry. The effects of acids and alcohol show that it contains albuminous matter; but beyond this it is impossible at present to make any precise statements.

This description may communicate an idea of the structure of the nervous chord in general. In particular situations this structure is considerably modified. The modifications to which we allude occur under two forms—ganglions (die Knoten), and plexuses (die Nervengeflechte). ∙

Every ganglion consists essentially of three parts,—l∙s∕, an exterior covering; 2ċ7, a collection of minute nervous filament; and, 3d, a quantity of peculiar cellular or filamentous texture, by which these filaments are connected, and which constitutes the great mass of the ganglion.

The ganglions are of two kinds, the spinal or simple, and the non-spinal or compound. These two kinds of [7:2:734]bodies differ from each other,—Is/, in the situation which they respectively occupy; 2d , in the kind of envelope with which they are invested; 3d , in the mode in which the nervous filaments pass through them and from them. By Wutzer, who considers the ganglion of Gasserius, the ciliary and the maxillary of Meckel, as cerebral ganglions, they are divided into three sets, those of the cerebral system, the spinal system, and the vegetative, or those connected with the organs of involuntary motion.^[82. De Corporis Humani Gangliorum Fabrica, &c. cap. i. ii. sect· 41, p. 52. ]

Void of the dense strong coat with which the others are invested, the cerebral ganglions consist of soft secondary matter, connected to the filaments of one, or at most two branches, and are arranged with less complexity. (Wutzer.)

The spinal ganglions are said to possess two coverings, one of which resembles the hard "cerebral membrane (meninx dura), the other the soft cerebral membrane (meninx tenuis, pia mater). The non-spinal or compound ganglions have also two coverings, which are merely different modifications of filamentous tissue, less dense and compact than in the former. Both these sets of ganglions being by maceration stripped of their tunics, and deprived of the soft, pulpy, cellular matter, are resolved into an innumerable series of nervous threads, most of which are minute and scarcely perceptible: all are continuous with the nerve or nerves above and below the ganglion. It appears that the nervous chord, when it enters the one apex of the ganglion, begins to be separated into its component threads, which diverge and form intervals, between which the delicate cellular tissue is interposed; and that these filaments are subsequently collected at the opposite extremity of the ganglion, where they are connected with the other nerve or nerves. Scarpa, to whom we are indebted for most of the knowledge we possess on this subject,^[83. Anatomicarum Annotationum liber primus de Nervorum Gangliis et Plexibus. Auct. Ant. Scarpa. ] compares the arrangement to a rope, the component cords of which are untwisted and teased out at a certain part. Lastly, In the simple ganglions, the filaments of which they consist invariably follow the axis of the ganglion; but in the compound ones they are found to rise towards the sides and emerge from them; and upon this variety in the direction and course of these filaments depends the variety of figure for which these two orders of ganglions are remarkable. These nervous threads (stamina s. fila nervea), described by Scarpa, correspond to the medullary filaments (fila medullaria) of Wutzer. According to this anatomist, these filaments, when about to enter the ganglion, lay aside their neurilem; yet they are sufficiently tough to resist a certain degree of tension.

Wutzer mentions a cluster of vesicles or cells (cancelli) in the filamentous tissue of the ganglion; but he was not enabled by any means, mechanical or chemical, to ascertain their exact nature.

The ganglions are well supplied with blood-vessels, derived in general from the neighbouring arteries. The intimate distribution is represented by Wutzer to be the following. The artery proceeding to a ganglion gives vessels to the filamentous tissue, and, perforating the proper coat, is immediately ramified into innumerable minute canals, the first order of which forms vascular nets on the inner surface of the tunic, while the residual twigs penetrate the flocculent texture, and the individual vesicles of the secondary or filamentous matter of the ganglion.^[84. De Corporis Humani Gangliorum Fabrica, &c. cap. ii. sect. 41. ]

This short exposition of the structure of the ganglions shows the mistaken notions of Johnstone, Unzer, Bichat, and others, on the structure and uses of these bodies. Ls∕, The idea, first advanced by Johnstone and Unzer, adopted by Metzger, Hufeland, Prochaska, Sue, and Harless, and afterwards applied with so much ingenuity by Bichat, that the ganglions are so many nervous centres or minute brains, is disproved by strict anatomical observation. 2d , That they are connected with the order of involuntary actions, and influence these actions, is a gratuitous hypothesis, and may be true or false without being necessarily the case. 3d , Lastly, we remark, as a circumstance of some importance, that the only difference between a ganglion and any other part of a nervous chord is, that in tĥe former the minute nervous filaments appear to be uncovered with neurilema, and lodged in a mass of cellular tissue, which is inclosed in the neurilematic capsule; while in the latter each nervous filament has its appropriate neurilema, and the cellular tissue, instead of being within, is on its exterior, and connects it to the contiguous filaments.

In various situations two, three, or more nervous trunks or chords mutually unite by means of some of their component threads, and after proceeding in this manner for a short space, again separate, but not in the same number of original trunks, or preserving the same appearance. In general, the number of chords into which they finally separate is greater than that of which they consisted before union. Three or four nervous trunks, for example, after uniting in this manner, will form on their final separation five or six nerves or nervous chords; and it is quite impossible to determine which of the latter order was derived from any one or two of the former, or what number of individual chords it has received from each. Between the two points, also, the first point of union and the last of separation, many of the more component threads are detached from two or more of their trunks, and, after first uniting with each other in an indistinct net-work, are again united to two or more of the nervous chords near the point at which they finally separate from the further end of union. This arrangement has been termed a plexus, plait, or τveaving, in consequence of the manner in which the nervous chords are interlaced or plaited together. The arrangement which we have noticed as consisting of the more minute nervous threads has been called a smaller plexus (plexus minor). It is a subordinate plexus within a larger one.

The best and most distinct example of a plexus is that commonly named the brachial or axillary. This, as is well known, is situate in the space contained between the broad dorsal muscle (latissimus dorsi) behind, and the great pectoral muscle before, and is formed in the following manner. The fifth, sixth, seventh, and eighth cervical nerves, and the first dorsal, after forming the usual connections (ansae), pass downwards from the vicinity of the vertebrae between the middle and anterior scaleni muscles, and, nearly opposite the lower margin of the seventh cervical vertebra, or about the level of the first rib, begin to be united by the component threads of each nerve. Threads of the fifth and sixth cervical unite, sometimes to form a single chord, in other instances to be connected a short space onward with threads of the seventh cervical in a similar manner. The seventh and eighth form two kinds of union. When the seventh is large, it divides almost equally into two chords orbranches, one of which is connected first with the fifth and sixth, [7:2:735]afterwards with the eighth, and with the first dorsal by interlacement of minute nervous threads. The other either passes downward to form one of the separate brachial nerves, or is also connected with the eighth cervical and first dorsal in a plexiform manner.

From this arrangement immediately arise the individual nervous branches which form the nerves of the arm, and which are named brachial nerves. The interlacement of minute nervous threads between the seventh and eighth cervical and the first dorsal, is what Scarpa has termed the plexus minor. He says it is peculiar, in being quite uniform, and in connecting those nervous branches which, from their subsequent destination, are called median and ulnar.

This description, though not generally applicable, will communicate some faint idea of the nervous unions and interlacements termed plexus or webs. For more minute information on the distribution, arrangement, and configuration of this part of the nervous system, we refer to the work of Scarpa already quoted.^[85. Annotation. Anatom, cap. iii. sect. 9, p. 94, 95. ]

Plexiform arrangements are not confined to the exterior regions of the body. They are more numerous internally; and almost all the organs of the chest and belly have each a plexus, sometimes two, from which they derive their nervous chords.

Plexiform arrangements are generally situate in the neighbourhood of blood-vessels, and in some instances inclosing considerable arterial trunks more or less accurately. Thus the axillary plexus surrounds the axillary artery. The coeliac artery is surrounded with the solar plexus; and the coronary, hepatic, splenic, superior mesenteric, and renal, are also surrounded with plexiform nervous filaments. In some instances these nervous filaments are so intimately connected with the arterial tubes as to lead some anatomists to consider them as forming a peculiar net-work surrounding the vessel, and to exercise great influence on the circulation. (Wrisberg, Ludwig, and Haase.)

It is remarkable that the structure of the nervous chords which form a plexus has either appeared so simple as not to demand particular attention, or is so obscure as to be never noticed. Have the nervous chords and threads in such situations their usual envelope? Is the nervous matter in the chords quite the same as in other situations? Are there any other means of union, save the nervous substance itself? We believe there is no doubt that every chord in a plexus is provided with its neurilema, as in other places; but this neurilema is generally thinner and more delicate, and the general neurilema seems to be wanting. Its mechanical properties of cohesion and resistance have not been examined.

The view now given of the structure and arrangement of the nervous plexus leads Scarpa to consider them as nearly allied to ganglions. The same separation of the component threads or filaments of the nerve or nerves, the same interlacement, and the same or similar formation of new chords, appear to take place in both orders of structure. A ganglion, indeed, he conceives, is a condensed or contracted plexus; and a plexus is an expanded or unfolded ganglion. The anatomical purpose of both appears to be simply a new arrangement or disposition of nervous branches, previous to their ultimate distribution in the tissues or organs to which they are destined. This is nothing but the expression of a fact,—the interpretation in intelligible terms of an arrangement of organized parts, without reference to any supposed uses.

I have already shown what is meant by the organic end or termination of a nerve. Although the nervous trunks are distributed in every direction through the animal body, they do not terminate in all the tissues or organs indiscriminately, and have been observed to be lost in the following only: Isí, The proper organs of sensation, the eye, ear, nose, palate, and tongue; 2dly, the muscles, whether subservient to voluntary or to involuntary motion, as the heart, stomach, intestines, &c.; 3dly, the mucous surfaces; 4thly, the skin; ĩsthly, glands, salivary, liver, kidneys, &c.; 6thly, bones.

Nerves, therefore, are not organs of general distribution. According to Bichat, they have never been traced to the following tissues :—the cartilages, both articular and of the cavities; fibrous textures, viz. periosteum, dura meninx, capsular ligaments, aponeurotic sheaths, aponeurosis in general, tendon, and ligament; fibro-cartilaginous textures—those of the external ear, nose, trachea, and eyelids (cartilages of other authors); the semilunar cartilages of the knee-joint; those of the temporo-maxillary articulation; those of the intervertebral spaces; marrow; the lymphatic glands.

To this we may add the testimony of Walter of Berlin, who, after several laborious researches, came to the conclusion that the pleura, the pericardium, the thoracic duct, and the peritoneum, receive no nerves, and that, contrary to the opinions of the most eminent recent anatomists, no nerves terminate in the lymphatic or conglobate glands. Sometimes, indeed, these organs are perforated by one or two twigs, as he often had occasion to observe; but they instantly proceed to the next place assigned to them, and in which they are finally lost.^[86. Prafat. Tab. Nerv. Thoracis et Abdominis, J. G. Walter. Berolini, 1783. ] If, after this conclusion of Walter, personal testimony can be of any use, I may add, that I have examined the dura mater, the periosteum, and most of the synovial membranes repeatedly, to discover nervous filaments in them, and always without success; and I may say the same regarding the absence or non-appearance of nerves in the peritoneum and pleura.

The nerves have different uses in the different organs and tissues to which they are distributed. 1. In the organs of sensation they receive the material impressions made on the mechanical part of the organ. In the mucous membrane of the nasal passages, the filaments of the olfactory nerve are affected by aromatic particles, dissolved or suspended in the air. In the eye the retina receives the last image formed by the transmitting powers of the transparent parts. In the ear the terminations of the auditory nerve are affected by the oscillations or minute changes in the fluid of the labyrinth, occasioned by the motions of the tympanal bones. In the palate, tongue, and throat, the gustatory nerves are affected by sapid bodies dissolved in the mouth, or applied in a fluid state to the mucous membrane of that cavity. 2. In the system of voluntary muscles, the nerves retain the action of the muscular fibres in a state of uniformity and equality; and keep them obedient to the will. In the involuntary muscles they appear merely to keep their action equable, regular, and uniform; and in both they maintain a communication, consent, or harmony of action between different parts of the same system of organs, or even between organs concurring to the same function. 3. In the glandular organs the nerves certainly exercise some influence over the process of secretion; but what is the exact nature of this influence, or in what degree it takes place, is quite uncertain. This may be said to comprehend all that [7:2:736]is accurately known regarding the uses of the nerves. Every other doctrine relating to sensibility, sympathy, irritability, &c. is either unfounded, not proved, or altogether imaginary and hypothetical.

In the foetus the nerves are developed with remarkable perfection. I cannot speak from personal observation much earlier than the sixth month, when I have found the nerves of the extremities and voluntary muscles large and distinct. At the eighth month they are still more conspicuous. The anterior crural nerves are in the form of flat white cords, one and a half line broad, and their branches like good-sized threads. The sciatic is still more distinct. In the form of a thick cylindrical cord, fully a line in diameter, and not unlike a piece of whipcord, it is tough, stringy, and resists tension; and its constituent threads are well marked. I immersed a portion of this nerve three and a half inches long in aquapotasses, when it first became much firmer and denser than before, assumed in two days the satin fibrous appearance first described by Fontana, and at length by solution of the nervous matter was separated into chords and neurilematic canals. In this state, preserved in spirit of turpentine, it conveys a tolerably correct idea of the arrangement of the neurilematic canals.

The nerves of the involuntary muscles are equally distinct in proportion. Those of the lung, heart, and splanchnic system are distinct and manifest at the eighth month.

The neurilem is much more vascular in the foetus than in the adult. In the same foetus of about eight months I found the neurilem of the sciatic nerve, from the ischiatic notch to its divarication in the ham, covered with a thick net-work of minute vessels, all injected with dark blood.

CHAP. II. THE PARTICULAR TISSUES.

- Cerebral Substance, — Erain. ( Cerebrum.)

The brain or central part of the nervous system may be regarded as a continuous organ, consisting of three divisions,—the convoluted, the laminated, and the smooth or funicular portions. Of these divisions, which are distinguished according to the peculiar external configuration of each, the first part corresponds to what is named the brain proper (cerebrum) ; the second to the small brain (cerebellum) ; and the third to the oblong production contained in the vertebral column, and known under the name of the spinal chord.

The convoluted portion presents two surfaces, an outer or convoluted, and an inner or figurate. The laminated portion in like manner presents two surfaces, an outer or laminated, and an inner or central. The third has only one surface, which is exterior. These different surfaces, and their mutual relations, will be more minutely explained afterwards. At present we shall examine its physical and anatomical characters as an organic substance.

’ The three divisions of the central part of the nervous system are composed of a peculiar substance, which may be denominated cerebral matter, inclosed in delicate vascular membranes. To exhibit the external characters of this substance, these membranes must be removed by careful dissection. When this is done, and the brain is inspected on its surface, and after sections, the cerebral matter is observed to vary in colour, consistence, and intimate structure in different parts of the organ. These varieties of cerebral matter are most easily distinguished, according to their colour, into white and gray or cincreous.

The white cerebral matter is of different shades in different parts of the brain. Its most usual hue is orangewhite, or orange-white inclining to reddish white, or purplish white. This is most distinctly recognised in the mesolobe (corpus callosum), and in the body named hippocampus major. The consistence of the white cerebral matter is considerable. It is in general more tenacious and cohesive than the gray matter, and when indurated is less brittle.

A section made by a sharp scalpel appears smooth and of a uniform colour, traversed by reddish points and streaks. It presents nevertheless different appearances in different directions. In certain parts, for example the mesolobe, it presents the appearance of minute capillary lines, arranged in parallel juxtaposition, and giving what is named a fibrous appearance. In other regions, however, as in the white matter of the optic chambers, this cannot be recognised.

White cerebral matter has been examined microscopically by Della Torre, Prochaska, the Wenzels, Sir Everard Home, and Μ. Bauer.

If we trust the observations of Father Della Torre, the white and gray substance of the brain, cerebellum, medulla oblongata, and spinal chord, consist of an aggregation of infinite transparent globules, floating in a pellucid, crystalline and somewhat viscid fluid. The only difference which he admits among the matter of these several parts is, that he represents the globules to be largest in the brain, smaller in the cerebellum, and still more minute in the medulla oblongata and spinal chord. The arrangement of these globules in the central portion of the nervous system he further represents to be promiscuous.

Prochaska placed on a thin plate of glass minute slices of cerebral matter, so thin that they were translucent; and in this state he found it consist of innumerable globular particles, united by delicate, pellucid, flocculent matter, like filamentous tissue. These globules varied in size even in the same part of the brain. In general, however, he found them both in the brain and cerebellum to be rather more than eight times smaller than the globules of the blood. He was unable to ascertain any thing regarding their intimate structure.

The Wenzels found the white cerebral matter to consist of very minute globules, or roundish atoms, resembling spherical cells containing proper medullary or white cerebral substance. The dimensions of these globules they did not attempt to estimate; but represent them in general as exceedingly minute, and all of the same size. They could not recognise any connecting medium. The globular appearance was retained in portions of brain exposed to the action of alcohol and muriatic acid, and in those even which had been dried after induration in alcohol.

Μ. Bauer placed a thin slice of white cerebral matter on a plate of glass previously moistened, and allowing a drop of water to fall on it, held obliquely, and thereby to diminish its cohesion, brought into distinct view innumerable loose globules, many fragments of fibres of single rows of globules, and bundles of fibres, some of considerable length.

The use of the water in this mode of examination is to dissolve and remove a viscid, gelatinous, semifluid substance, on which the adhesive properties of the white matter seem to depend. If the water is not used, the brain adheres to the glass, and the globular appearance cannot be recognised.

These globules vary in size from 1/2400 to 1/4000 of an inch in diameter; the general or average size being Those of the white matter are largest, that is 1/2400. They are translucent, whitish, and arranged in lines or rows of single globules, which are attached to each other by the viscid semifluid mucus. The strings or rows of globules are connected into bundles or fasciculi by the same medium.
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There is reason to believe that the translucency of the globules depends on an albuminous fluid, which on immersion in alcohol or acids is coagulated, and thereby rendered opaque.

When a portion of white cerebral matter is immersed in boiling oil, or is steeped for a few days in alcohol, dilute nitric or muriatic acid, or in a solution of corrosive sublimate, it acquires great firmness and solidity, and may be torn or broken like a piece of cheese, which it could not be before, in consequence of its tenacity. Certain parts, for example the mesolobe, appear then to be distinctly fibrous, or to consist of long capillary lines placed in close juxtaposition. On the length of these filaments or fibrils, however, nothing is ascertained. It is also undetermined whether the white cerebral matter is in all parts arranged in the fibrous manner.

White cerebral matter is well supplied with bloodvessels. These, indeed, are minute; but they consist both of vessels containing red and colourless blood. The division of these vessels gives rise to the appearance of red points (punctula) and streaks, which are exhibited on the surface of sections. It is believed to be less vascular than the gray cerebral matter.

On the chemical constitution of white cerebral matter we possess no accurate information; all the chemical analyses hitherto made having been directed to brain, without distinction of its different varieties. From the circumstance, however, of its becoming indurated on immersion in alcohol, acids, and solutions of corrosive sublimate, it is manifest that it contains much albumen. It is rendered yellow by nitric acid. If a portion of indurated brain be placed in the sun, or in a warm atmosphere, an oily or unctuous fluid exudes from its surface, which shows that it contains fatty matter; and if brain be immersed in ether, this fatty matter is partially removed. From the analysis of Vauquelin, it may be inferred that the white cerebral matter contains the 4∙43 per cent, of white adipose substance found by that chemist in his analysis. It is also believed to contain phosphorus.

The gray or cincreous cerebral matter, though variable in colour like the white, is in general a mixture of ash-gray and wood-brown, darker than the former, but lighter than the latter. The colour varies at different ages. It is light in early life, and deeper as life advances.

The gray cerebral matter is softer and less viscid and tenacious than white cerebral matter. It is distinctly granular, both in the external surface and when torn or broken. This appearance, however, is most distinctly recognised after induration in alcohol or acidulous liquors. In the convoluted part of the brain, where it is most abundant, it does not present the fibrous or parallel linear arrangement, and is merely an aggregated mass of numerous minute granules. It is uncertain whether it presents the fibrous arrangement in other parts of the brain. An appearance of this kind is recognised in the unciform bundle at the inner end of the fissure of Sylvius, and also in the streaked bodies and the annular protuberance. But the appearance alluded to seems to depend not on the genuine fibrous arrangement of the granules of the gray matter, but merely on the gray matter being deposited in streaks and lines between the white. Meckel nevertheless maintains that the gray matter is also fibrous.

According to the observations of Sir Everard Home and Μ. Bauer, the gray cerebral matter consists of minute globular atoms, smaller than those of the white matter, or varying from - 3 √0θ to M⅛o an ιnc ^ 1 ln diameter. These globules appear to be united, though more loosely, by a sero-albuminous fluid of a yellower tint than that of the white matter. Home supposes this albuminous fluid to be less abundant in the gray matter.

Gray cerebral matter is well supplied with blood-vessels, which are large and numerous. It must not be imagined, however, that all the vessels which are observed to enter this substance are therefore distributed to it. These large vessels necessarily penetrate the gray matter of the convoluted surface before they reach the white matter in the centre; and though they send branches to the former, they are ultimately distributed to the latter. The gray cerebral matter has been supposed to be more vascular than the white; but the circumstance now stated renders this doubtful. The statement of Sir Everard Home, that “the finest and most delicate branches of the arteries and veins are only found in the eortical, í. e. the gray substance,” is contradicted by observation; for the vessels are certainly in general larger and more distinct in this than in the white matter. But if they are larger in the former, they are more numerous in the latter. On the whole, perhaps, there is little difference between the vascularity of the white and gray substance of the brain.

The chemical constitution of gray cerebral substance has not been accurately examined. The results of analysis show, nevertheless, that it contains albuminous matter to the amount of about 7 per cent., with 0∙70 of a peculiar red adipose matter, which is probably the cause of the peculiar colour.

These two varieties of cerebral matter are combined in various modes and proportions in the brain. In general the gray matter is found on the exterior, for instance on the convoluted surface of the brain, and on the laminated surface of the cerebellum; while the white matter is arranged in the central parts. Gray matter, nevertheless, is found in the interior, in the streaked bodies and optic thalamus, and in the moriform bodies (corpora dentata) of the cerebellum and olivary eminences.

Besides the two varieties of substances now mentioned, a third, of a deeper shade, is found in the brain. Thus, in the centre of the cerebral limbs is a quantity of cerebral matter of a dark or ink-spotted tint, which Vicq d’Azyr therefore named the black spot (locus niger) of the limbs of the brain. The nature of this black spot, which is quite uniform, is entirely unknown. It appears merely to be a modification of the gray matter.

A yellow-coloured substance has also been supposed to exist in the centrum semicirculare geminum, a narrow band between the striated body and optic thalamus. This substance is certainly firmer than the adjoining white and gray matter, and it is further peculiar in possessing a sort of tint between wax-yellow and wine-yellow. It is highly vascular. Of its other peculiarities, however, we know nothing; and we must be satisfied with regarding it as an anomalous species of animal substance, approaching to gray cerebral matter in colour, but infinitely firmer and more tenacious.

The parts named pituitary and pineal glands present several peculiarities deserving attention; but these more properly come under the head of Special than of General Anatomy.

Flesh, Muscle. (Mu¢,—Musg,— Musculus, — Laxertus, — Tori.) Muscular Tissue. ( Tissu Musculaire.)

The ordinary appearance of the substance named flesh or muscle is familiar; and it is unnecessary to enumerate those obvious characters which are easily recognised by the most careless observer. A portion of muscle, when carefully examined, is found to consist of several animal[7:2:738] substances. It is traversed by arteries and veins of various size; nervous twigs are observed to pass into it; it is often covered by dense whitish membranous folds (fasciae), or by serous or mucous membranes, all which shall be examined afterwards; and it is found to contain a large proportion of filamentous tissue. But it is distinguished by consisting of numerous fibres disposed parallel to each other, and which may be separated in the same manner by proper means. The appearance, arrangement, and characters of these fibres demand particular fiotice.

According to Prochaska, muscle in all parts of the body may be resolved, by careful dissection, into fibres of great delicacy, as minute as silk filaments, but pretty uniform in shape, general appearance, and dimensions. Their diameter appears not to exceed the 4 q⅜ 5 ∙ 0 part of an inch, whatever be their length. They seem all more or less flattened or angular, and appear to be solid diaphanous filaments. Prochaska, not doubting that these muscular threads (fila carnea) are incapable of further division, terms them primary muscular fibres.

The microscopical examination of the atomic constitution of the muscular filament, which was first attempted by Lecuwenhoeck, and afterwards prosecuted by Della Torre, Fontana, Monro, and Prochaska, has been recently revived by Μ. Bauer, the indefatigable assistant of Sir E. Home. From the observations of this accurate inquirer, each muscular filament appears to consist of a series of globular or oblong spheroidal atoms, disposed in a linear direction, and connected by a transparent, elastic, jelly-like matter. (Phil. Trans. 1818, 1826.)

The primary muscular fibres are placed close and parallel to each other, and are united in every species of muscle into bundles (fasciculi, lacerti) of different but determinate size; and according as these bundles are large or small, the appearance of the muscle is coarse or delicate. In the deltoid the bundles are the largest. In the vasti, glutoei, and large pectoral muscles the bundles are greatly larger than in the psoae. In the muscles of the face, of the ball of the eye, of the hyoid bone, and especially in those of the perineum, these bundles are very minute, and almost incapable of being distinguished. The number of ultimate filaments which compose a bundle varies in different muscles, and probably in different animals. In a muscular fibre of moderate size in the human subject, Prochaska estimates them to vary from 100 to 200; and, in animals with larger fibres, at double, triple, or even four times that number. There is reason to conclude, from correct microscopic observation, that the largest do not exceed the ⅛ of an inch, and that the smallest are not less than ⅛

By cutting a muscle across, these bundles are observed to differ, not only in size, but in shape. Some are oblong and rhomboidal, others present a triangular or quadrangular section, and in some even the irregular pentagon or polygon may be recognised.

These bundles are united by filamentous tissue of various degrees of delicacy, as may be shown by the effects of boiling; and the muscle thus formed is penetrated by arteries, veins, and nervous twigs, and is inclosed by filamentous tissue, which often contains fat.

This fascicular arrangement appears to be confined to the muscles of voluntary motion. It is not very distinct in the heart or diaphragm; and in the urinary bladder and intestinal canal it is not recognised. Nor is the parallel arrangement of the ultimate filaments always strictly observed in the involuntary muscles. The component fibres of this order of muscles are often observed to change direction, and unite at angles with each other. This fact, which was observed by Lecuwenhoeck,has been verified by Prochaska.

The colour of muscle varies. In man and the mammiferous animals, at least adult, it is more or less red; in many birds and fishes it is known to be whitish; in young animals it is grayish or cream-coloured; and the slender fibres which form the middle coat of the intestines in all animals are almost colourless. The colour of the muscles of voluntary motion in man is red or fawn; but repeated washing or maceration in alcohol or alkaline fluids renders them much paler.

The examination of the physical properties of muscle has occupied the industry of Muschenbroek, Croone, Browne Langrish, Wintringham, and others of the iatro-mathematical school. I cannot perceive that minute knowledge of these properties is of much moment to the elucidation either of its sound or its morbid states. Amidst the variable results obtained in such an inquiry, the only certain point is, that muscular fibre has less tenacity and mutual aggregation than most other tissues. It sustains much less weight and force of tension without giving way.

Chemical analysis has not yet furnished any satisfactory results on the nature of muscular tissue; but the general results of the numerous experiments already instituted show that muscle contains fibrin, albumen, gelatine, extractive matter (osmazome), and saline substances. It is difficult to say how far the gelatine is to be regarded as proper to muscle, or derived from the filamentous tissue in which it certainly exists. The saline matters are common to muscle with most other organic substances. There is reason to believe that fibrin in considerable quantity, and albumen and osmazome in smaller proportion, are the proper proximate principles of muscle. Though the various proportions of these principles have been stated in numbers by chemists, it is impossible in the present condition of animal chemistry to place any reliance on them. It is also to be remembered that the relative proportion of the proximate principles varies at different periods of life. In early life the muscular fibre contains a large proportion of gelatine, and very little albumen, fibrin, or osmazome. In adult age, however, the gelatine is very scanty, and the fibrin is abundant. The albumen and gelatine found in muscle seem to be derived chiefly from the filamentous tissue and the aponeurotic intersections.

During life the muscular fibre possesses the property of shortening itself or contracting under certain conditions. These may be referred to the following heads: 1∙⅛ The will in the voluntary muscles; 2d , proper fluids in the involuntary muscles, as the blood to the heart, articles of food or drink in the stomach, chyme in the small intestines, excrement in the large intestines, urine in the bladder, &c.; 3rf, mechanical irritants in all muscles; 4∕7z, chemical irritants; and, ĩ>th, morbid products generated in the course of disease.

This property of contracting has received various names: contractility, vis contractilis of L. Bellini; irritability of Glisson; vis Vitalis of De Gorter and Gaubius; excitability, mobility, vis insita, vis propria of Haller; and the organic contractility of Bichat. It is peculiar to muscular fibre, and is found in no other living tissue.

The inquiry into the properties peculiar to muscles, and the influence of the brain and nerves over muscular contraction, form an interesting subject of investigation, on which many facts have been communicated since the time of Haller and Whytt, and especially within the last ten years by Nysten, Le Gallois, Wilson Philip, Bell, Magendie, Flourens, Fodera, and Rolando. But it is too extensive to be considered in this place; and, for information [7:2:739] on the subject, I refer to the ordinary physiological works, and to those journals in which these researches are detailed.^[87. Elementa Physìologìoe, tom. iv. lib. xi. sect. 2; Whytt on the Vital and Involuntary Motions : Journal de Physiologie, tom. i. ii. &c.; Archives Générales, passim. ]

The muscles have been divided, according to the manner in which the phenomena of contraction take place, into, Isŕ, muscles obedient to the will, or voluntary; 2d , muscles not under the influence of the will, or involuntary; and, 3d , muscles of a mixed character, the motions of which are neither entirely dependent nor independent on the will.

The first order comprehends all the muscles of the skeleton; the second includes the hollow muscles, as the heart, stomach, and intestinal canal; and in the third are contained such muscular organs as the diaphragm, intercostal muscles, bladder, rectum, &c.

The muscles have also been distinguished, according to their mechanical shapes, into long muscles (musculi longi, vel teretes), broad muscles (musculi lati), and irregular muscles, or those of mixed form. The long muscles are found chiefly in the extremities; the broad muscles in the trunk; and those of irregular shape either in the trunk, or passing from this to the extremities. From the direction of their fibres, several of them are distinguished into penniform and semipenniform.

Sinew, Tendon. ( Tendo.) ’ Sinew or tendon was united by Bichat with ligament, fascia, aponeurosis, and periosteum, under the general name of fibrous system ; and the substance of this arrangement has been adopted by Gordon, Meckel, and Bedard. From personal observation, however, I am inclined to regard tendon as essentially distinct, at least in the present state of knowledge, from these substances. Examined anatomically, it does not bear a very close resemblance to any of them; and in its known chemical properties it is considerably different.

The appearance of this substance must be familiar. Almost cylindrical in shape, but flattened at the muscular end, and tapering where inserted, a tendon consists of numerous white .lines as minute as hairs, of satin-like glistening appearance, placed parallel and close to each other. A tendon is easily divided, and torn into longitudinal or parallel portions; and by the forceps very minute fibres may be detached and removed with ease, its whole length. These facts show the great tenacity of this tissue, and the regular parallelism with which the component fibres are united. The last circumstance distinguishes them completely from ligaments and periosteum, in which the fibres cross in all directions, and in consequence of which these tissues cannot be so easily split or separated. These fibres are united by filamentous tissue.

Tendon is softened and more easily separable by maceration in water or alkaline fluids; it is crisped by acid fluids, and rendered translucent by immersion in oil of turpentine. It has not been injected, but it is presumed to have blood-vessels and absorbents. No nerves have been traced into it.

Tendon when boiled becomes soft and large, assumes the appearance of a transparent gelatinous substance, and finally, if the boiling be continued, is dissolved and converted into gelatine. This fact, which is well known to cooks, who prepare jellies from tendinous parts of young animals, shows that tendon consists principally of gelatine, disposed in an organized form.

A species of flattened tendons, to which the name of aponeurosis has been given, may justly be united with this tissue. The best examples are in the aponeurotic or tendinous expansion of the external oblique muscle of the abdomen, the aponeurotic part of the occipito-frontal muscle of the head, and the upper or broad end of the tendo Achillis. The anatomical structure and the chemical properties of each of these varieties of animal substance are quite similar, and somewhat different from that which has been termed fascia. White Fibrous System. Ligament. (Δεσμός, ο! ∆εβμo∕.) Periosteum, — Dura Mater, — Fascia.

Against the formation of this order of tissues fewer objections can be urged, though ligament and periosteum undoubtedly furnish its most perfect examples; and it may be doubted whether fascia ought to be referred to it, or arranged with tendon and aponeurosis. The dura mater, the tunica albuginea, and the fibro-synovial sheaths, are to be regarded as compound membranes.

Ligament and periosteum are easily shown to consist of strong whitish or gray fibres, as minute as threads or hairs, interwoven together in various directions, and thus forming an animal substance which is not to be split or torn asunder as tendon; but when ruptured by extreme force presents an irregular ragged surface or margin. Maceration in water or alkaline fluids separates the component fibres, and shows their irregular disposition more distinctly. They are crisped by affusion of boiling water, or immersion in acids; and they become translucent by immersion in oil of turpentine.

The properties of this tissue are chiefly physical. Those which are vital are referable to its organization and nutrition. That it is powerfully resisting, and is one of the toughest and strongest tissues in the animal body, is evinced not only by the numerous experiments recorded in the writings of the iatro-mathematical physiologists, but by the barbarous mode of punishment by rending the limbs asunder by horses. It is supposed to possess the exhaling ends of arteries and colourless veins. No nerves have been recognised; and Bichat expresses his ignorance of absorbents being traced into it.

Ligament when boiled yields a small portion of gelatine, but obstinately resists the action of boiling water, and retains both its shape and tenacity or cohesion. The crispation which it undergoes in boiling water, alcohol, and diluted acids, seems to indicate that albuminous matter forms its chief chemical principle.

As to their mechanical shape, the ligaments are divided by Bichat into two sorts; those in regular and those in irregular bundles. The former comprehends all the distinct clusters of ligamentous structure, which, sometimes in a cylindrical, sometimes in a flattened shape, connect the articulating ends of bones, and form the lateral ligaments of the various articulations. The latter consists of those loose parcels of ligamentous fibres which are found in various regions of the skeleton, not in regular cylindrical or longitudinal bands, but irregularly connecting bones not admitting of articular motion; for instance, at the symphysis pubis and the sacro-iliac junction. The division of Bedard into articular, non-articular, and mixed, is more comprehensive and more natural. The first are those which connect the articular extremities of different bones. The second are those which, attached to different parts of the same bone, convert notches into foramina, as in the orbitar arch and the supra-scapular hollow, or close openings, and [7:2:740] give attachment to muscles, as the obturator ligament. The last are those which, like the sacro-ischiatic or the interosseous ligaments of the fore-arm and leg, connect bones susceptible of little or no motion, and especially give attachment to muscles. The two latter species of ligaments approach closely in their characters, physical and anatomical, to periosteum, and are probably to be regarded as modifications of this membrane.

The articular or perfect ligaments are naturally divisible into two subgenera,—the capsular and the funicular.

The capsular ligaments, or the fibrous capsules (Bichat), consist of cylindrical ligamentous sheaths attached all round to the ends of the articulating bones, and intimately interwoven with the periosteal tissue. Consisting essentially of fibro-albuminous matter strongly compacted, they are surrounded by cellular tissue, or rather celluloso-adipose tissue, and are lined internally by synovial membrane. Though the most perfect examples of the capsular form of ligament are presented in the scapulo-humeral and coxo-femoral articulations, less complete ones, nevertheless, are seen in the other joints. In those of the knee and elbow, an arrangement of this kind may be demonstrated; and minute capsules may be shown to connect the oblique articular surfaces of the vertebrae with each other.

Yho funicular ligaments, which consist of round chords or flat bands, are employed in connecting the articular ends of bones either without or within the cavity of the joint. Of those of the former description, the best examples are seen in the elbow and knee joints, and in the wrist and ankle, where they are termed lateral ligaments (l. lateralia, accessoria). Of the latter instances are the round ligaments (ligamenta teretia) of the shoulder and hip joints, and the crucial ligaments of the knee-joint. These receive an investment of synovial membrane.

Of the white fibrous tissues, one of the most important is that denominated fascia. Consisting in intimate structure of long fibrous threads placed in parallel juxtaposition, sometimes obliquely interwoven and closely connected by filamentous tissue, it forms a whitish membranous web, variable in breadth, of some thickness and great strength. Fascia is perhaps, not excepting the skin, the most extensively distributed texture of membranous form in the animal body. It not only covers, if not the whole, at least by far the greatest part of the muscles of the trunk and each limb, but it sends round each muscle productions by which it is invested and supported, and even penetrates by minute slips into the substance of individual muscles. Of several of the large muscles it connects the component f∕arts, as is seen in the recti abdominis ; to many it affords points of origin or insertion; and to all it furnishes more or less investment and support. Most of the tendons, especially the flexor arid extensor tendons, are inclosed by it; and their synovial sheaths derive from it their exterior covering. At the extremities of the bones it is connected with the ligaments and periosteum, with which it is closely interwoven; and it forms a general investment to the articular apparatus.

Though fascia may thus be viewed as one membranous web consisting of many parts all directly connected with each other, it is the practice of anatomists to distinguish its divisions according to the region which they occupy. Thus, in the fore-part of the neck and chest is found a fascia, the relations and uses of which have been well described by Mr Allan Burns. In the cervical region we find a firm fascia descending from the occipital bone along the vertebrae, covering and connecting the muscles of each side till it reaches the loins, where, in the form of a thick strong membrane, it forms the lumbar fascia (fascia lum borum). It may further be traced over and between the glutaei muscles, connected afterwards with the broad femoral fascia (fascia lata), and thence over the knee and leg to the foot. Much in the same manner a membranous web, thinner and more delicate, but of the same structure, may be traced from the chest along the upper extremity, till at the wrist it is identified with the annular ligament, and in the hand with the palmar fascia. In all these situations the general fascial envelope sends slips or productions (fasciae intermusculares) between the muscles, and into their substance.

Yellow Fibrous System. Elastic Ligaments of John Hunter.

(Ligamenta Flava, — Ligamentum Nuchae, —Tissu Fibreux Jaune, Bedard.)

The yellow ligaments (jigamenta flava) which connect the spinous processes of the vertebrae to each other differ considerably from the articular ligaments and the periosteum, and suggested to Bedard the necessity of establishing a particular order of fibrous tissues, to which he applies the denomination of yellow or tawny fibrous system. Under this he includes also the proper membrane of the arteries; that of the veins and of the lymphatic vessels; the membranes which form excretory ducts; that of the air-passages; the fibrous covering of the cavernous body of the urethra, and perhaps that of the spleen. The actions and occasional distensions of which these parts are the seat require, it is said, a tissue, the resistance and elasticity of which may at once counteract any extraordinary effort, and cause them to resume their original state, when the distending cause ceases to operate. In the lower animals this purpose is more conspicuous than in the human subject. The posterior cervical ligament (ligamentum nuchae, Arab.; cervicis, Lat.) in the camel, giraffe, deer, and ox, counteracts the tendency to inclination of the head; and a similar membrane strengthens the abdominal parietes, and resists the weight and distending power of the viscera. In the feline tribe an elastic ligament inserted into the unguinal phalanges retains them extended so long as the muscles do not alter their direction. The shells of the bivalve molluscous animals, as oysters, mussels, &c., are opened by a similar fibrous tissue as soon as the muscles which close them are relaxed.

The disposition of the component fibres is the same in the elastic as in the common white fibrous system. Their colour, which is yellow or tawny, is generally more distinct in the dead subject. They are said to be less tenacious, but more elastic, than those of any other tissue. In respect to chemical composition, they appear to contain a considerable quantity of fibrin in a peculiar condition, combined with some albumen and a little gelatine. Their other properties are not very conspicuous.

Bone, (θδηον, — Ossa, — Tissu Osseux,— Die Knochen.)

Bone, which is the hardest and most durable of the animal solids, may be defined to be an organized substance, consisting of a combination of animal and calcareous matter, and constituting by its solidity the chief support of the soft parts generally.

In the vertebrated animals it is moulded into pieces of definite shape and size, which are connected either by ligaments, cartilage, or fibro-cartilage, and which constitute the skeleton of the animal. In the mammalia and birds these pieces appear in their most perfect characters, as to solidity, mechanical shape, and numerical extent. In the human subject, though in these respects they partake of the characters common to the bones of the mammalia⅛ in several senses these characters are more conspicuous than in the lower animals.
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1. The bones of the human skeleton are distinguished, according to the varieties of mechanical figure, into long and cylindrical bones (ossa longa sive cylindrica), flat bones (ossa lata sive plana), and short or irregular bones (ossa brevia sive mixta).

The long bones are confined to the extremities, where they are subservient to the locomotive apparatus, by acting alternately as points of support and as levers movable by the muscles in different directions. Placed in the centre, they are surrounded almost entirely by muscles; and are observed to diminish in length, but increase in number, the farther they recede from their attachment to the trunk. From this inverse arrangement it results that near the trunk the members are distinguished for extent, and remote from it for variety and multiplicity of motion.

The long bones agree in presenting cylindrical or prismatic shafts (diaphyses) terminated by large, bulky, and extensive extremities (epiphyses). The former arc generally small and slender∙ compared with the latter and with the size of the limb, and thus afford room for the bellies of muscles attached to them. The large size of the latter is well suited for the extent of the articular surfaces; and being covered by slender tendons and the taper extremities of muscles, they do not in general add to the bulk of the member.

The shafts of the long bones are in general marked by longitudinal rough lines, to which muscles or fasciae are attached, and between which are found plane or hollow surfaces for lodging the bellies of the muscles. These lines are rarely straight; and the slight obliquity which they observe gives the bone the appearance of being twisted. This is well seen in the humerus and tibia.

The extremities of the long bones are marked in general by eminences and hollows, or processes (apophyses) and depressions (foveoe ; fossae). These inequalities, if tipped with cartilage and synovial membrane, are for the purpose of articulation with other bones. When they are simply formed of bone, they are for the attachment either of ligaments or tendons.

The shafts of the long bones consist chiefly of dense compact bone, containing in the adult a longitudinal cavity, which is easily exposed by a longitudinal section of the bone. This cavity is not cylindrical, but tapers considerably at each end; nor is it in all instances equally complete. Largest and most capacious about the middle, where it is bounded by the solid, compact, bony walls of the diaphysis, as the latter diminish in density they increase in bulk by the formation of numerous minute intersecting columns of bone, which progressively increasing in number towards the end of the shaft, contract the cavity, until at length it is obliterated in the lattice-work and cells (cancelli) formed by their mutual intersection. This cavity is the medullary canal. It is seen in its most perfect form in the humerus and femur, in the tibia and fibula, and in the radius and ulna. In the phalanges it can scarcely be said to exist. The two forms of bony structure demonstrated in such a section are distinguished as the dense or compact, and the loose, reticular, or cancellated.

The medullary cavity is lined by a vascular filamentous membrane, with numerous cells, containing the variety of animal fat denominated marrow. The effect of this arrangement is to render the bone lighter than if perfectly solid, without any diminution of strength. This cavity is wanting in the original formation of the bone; and it begins to be formed when the matter of the diaphyses becomes dense and compact. It is again obliterated in consequence of fracture or other injuries, succeeded by adhesive or depository inflammation, when it is filled by gelatinous animal matter; and it is once more excavated as the walls of the diaphysis acquire solidity.

The flat bones are in general less connected with the locomotive apparatus than with the protecting part of the skeleton. By mechanical configuration they serve to contain various organs essential to the economy; and when they admit of motion, this is rarely locomotive, but connected with the purposes of the contained organs. The bones of the cranium and pelvis furnish the best examples of bones destined solely to protect, and as locomotive agents affording only points of support. The ribs, again, which are to be viewed as flat bones, not only form the protecting walls of the chest, and furnish support to the muscles of the upper extremities, but further undergo a slight motion, by means of which the dimensions of the chest are alternately enlarged and diminished. The vertebrae combine the characters of flat bones and irregular bones, approaching by their spinal plates to the former class, and by their bodies to the latter.

In number the flat bones vary according to the purpose to which they are applied, and the nature of the cavities which they form. In the cranium and pelvis their numerical extent appears to bear relation chiefly to the facility of ossification,—a process which advances with equal rapidity in each individual piece. In the chest, again, this property is regulated by the kind of motion which the ribs are destined to undergo. The vital organs of circulation and respiration would no doubt have been more securely protected had they been inclosed, like the brain, in a continuous and complete osseous case; but by this arrangement the motions of inspiration and expiration must have been very limited.

The flat bones agree in being convex and concave in opposite directions; in possessing two surfaces, an external and an internal, and a circumference; and in consisting of an external and internal table or thin plate of bone, with loose cancellated structure interposed. This arrangement is most conspicuous in those of the cranium, in which the cancellated structure is distinguished by the name of diploe. It is nevertheless equally distinct in the ribs, the scapula, and the pelvic bones. In some instances in the latter, the diploe is obliterated, and the two tables approach each other so closely, that they form one bone; and occasionally this is destroyed, and the bone appears perforated. These effects are the result of longcontinued muscular action.

The cancellated structure of the flat bones is lined by a vascular filamentous membrane, containing a small proportion of marrow, less oleaginous than that of the long bones, and entirely resembling those of the cancellated structure of their epiphyses.

The short bones are situate in parts requiring the combination of mobility and solidity; for example, the vertebral column, the carpus and metacarpus, the tarsus and metatarsus. Considerable extent of surface, numerous articular and ligamentous connections, with few muscular or tendinous insertions, are their leading external characters.

They consist of a single thin external plate of bone, inclosing a large proportion of cancellated structure, lined by vascular filamentous tissue, containing semifluid marrow, without much oil. While this arrangement combines very small specific gravity with sufficient firmness and solidity, it renders them more liable to derangements of organization than other parts of the osseous system.

Though the bones are thus distinguished according to general characters, it is often impossible to apply them accurately. The same bone may unite the characters of long and short bone, or flat and short bone, or long and [7:2:742] flat bone. All the long bones indeed are in their epiphyses similar to the short bones.

In external figure the bones present certain eminences or processes (apophyses), and pits or cavities (foveoe; fossae). The eminences are either articular or non-articular. The former, which are covered with cartilage or fibro-cartilage 1 belong to the subject of the connections of bones. The latter may be referred to three heads: Isí, eminences of insertion for ligaments, tendons, or aponeuroses; 2d, eminences of reflection for the transit of tendons round a pulley; and, 3d , eminences of impression, or those which correspond to various soft parts in contact with the bones.

The eminences of insertion appear in various shapes, and are distinguished into tuberosities and tubercles (tubera), spines (spinoe) or spinous processes, styloid processes (styli), crests (cristae), and lines (lineoe), which are generally rough and elevated. These impressions are always more conspicuous in the male than in the female, in the old than in the young, in the robust and muscular than in the delicate and feeble, and in carnivorous than in herbivorous animals. In some instances, as in the case of the ischial tuberosity, the great trochanter and anterior tuberosity of the humerus, the eminences present individual facettes for the attachment of each tendon or muscle.

Of the eminences of reflection, the best examples are in the unciform process of the pterygoid process of the sphenoid bone, and the lower extremity of the fibula.

The depressions are either articular or non-articular. The latter consist of cavities of insertion, reception, transmission and motion, impression and nutrition.

The first, which give attachment to ligaments, tendons, or aponeuroses, are useful in augmenting the extent without increasing the size of bones. The pterygoid cavities, the digastric fossa, and that at the base of the great trochanter, afford examples of these cavities.

Of the cavities of reception, examples are seen in the cerebral and cerebellic fossae, and in the grooves for arteries or nerves; for instance, that at the lower margin of the ribs, and the various openings in the cranium for the transit of vessels and nerves.

Cavities of motion are those over which tendons play in the contraction of muscles; the bicipital groove, the hollow between the ischial spine and tuberosity, and that in the fibula for the peronaei, are examples.

The cavities of impression alternate with the eminences, and are to be regarded as in general the cause of these eminences.

The cavities of nutrition are those minute orifices through which vessels convey to the substance of the bone, or the medullary membrane, the materials of its nutrition. Each long bone has one considerable hole of this kind in its. shaft, and numerous minute ones in its extremities. The former is the orifice of a canal to the medullary cavity. The latter are supposed to belong chiefly to the cancellated structure.

2. Several attempts have at different times been made to ascertain the atomic constitution of bone, but without much success. Malpighi, though he corrected the extravagant fiction of Gagliardi regarding the osseous plates and nails, fancied bones to be composed of filaments, which Lecuwenhoeck represented as minute tubes (in-bulï). By Clopton Havers, again, the ultimate particles of bones were imagined to be fibres aggregated into plates (laminoe) placed on each other, and traversed by longitudinal and transverse pores (pori). ^[88. The principal authors on the structure of bone are, Dominici Gagliardi Anatorne Ossium, novis inventis illustrata. Romae, 1689. Malpighi, De Ossium Structura : Op. Post. Clopton Havers, Osteologìa Nova. London, 1691. Delasone, Mémoire sur l’ Organisation des Os : Mém. de l’ Académie, 1751. G. C. Reichel, De Ossium Ortu atque Structura. Lips. 1760. Ext. in Sandifort Thesaur. vol. ii. p. 171· Antonii Scarpa de Penitiori Ossium Structura Comment. Lips. 1799. Republished in De Anatomé et Pathologia Ossium Commentarii, Auctoŗe A. Scarpa. Ticini, 1827- Papers by Mr Howship in the 6th and 7th volumes of the MedicoChirurgical Transactions. ] This view was adopted by Courtial, Winslow, Palfyn, Monro, and Reichel, who was at some pains to demonstrate this arrangement of plates and minute tubes by microscopical observation. These notions were first, questioned by Scarpa, who, in 1799, undertook to show by examinations of bone deprived of its earth by acid, and long macerated in pure water, that it consists, both externally and internally, of reticular or cellular structure. So far as I understand what idea this eminent anatomist attaches to the terms reticular and cellular, I doubt whether this opinion is better founded than any of the previous ones. After repeating his experiment of immersing in oil of turpentine bone macerated in acid, I cannot perceive the reticular arrangement which Scarpa describes. Recently bone has been submitted to microscopic examination by Mr Howship, who revives the opinion of the existence of minute longitudinal canals, as taught by Lecuwenhoeck, Havers, and Reichel, but with Scarpa maintains the ultimate texture not to be laminated, but reticulated. Lastly, the existence of fibres and plates, which is admitted by Blumenbach, Bichat, and Meckel, apparently on insufficient grounds, is to be viewed as an appearance produced by the physical, and perhaps the chemical qualities of the proper animal-organic matter of which bone consists. Though it does not demonstrate, it depends on, the intimate structure of this body.

The minute structure or atomic constitution of bone is probably the same in all the pieces of the skeleton, and is varied only in mechanical arrangement. When a cylindrical bone is broken, and its surfaces are examined with a good magnifying glass, or when minute splinters are inspected in a powerful microscope, it appears to be a uniform substance without fibres, plates, or cells, penetrated everywhere by minute blood-vessels. Its fracture is uneven, passing to splintery. In the recent state its colour is bluish-white; but in advanced age the blue tinge disappears. Delicate injection, or feeding an animal with madder, shows the vascularity of this substance.

To have a clearer and more accurate idea of the minute structure of bone, it is requisite to break transversely a long bone, and examine its fractured surface by a good glass, or to examine in the same manner the transverse fracture of a long bone which has been burnt white in a charcoal fire. The broken surface presents a multitude of minute holes, generally round or oval, which are larger towards the medullary cavity, but become exceedingly minute towards the outer surface of the bone. Of these minute holes no part of the bone, however compact in appearance, is destitute; and the only difference is, that they are more minute, and more regularly circular towards the outer than towards the medullary surface. These circular holes are transverse sections of the tubuli of Lecuwenhoeck, the longitudinal pores of Havers (Osteologia, p. 43 and 46), the pores and tubuli of Reichel, and the longitudinal canals of Howship. They communicate with each other by means of their great multiplicity and slight obliquity and tortuosity. They contain not blood-vessels exclusively, but divisions of the vascular filamentous tissue, which secretes the marrow. They are seen very distinctly in bones which have been burnt. After many care[7:2:743]ful examinations, I have never been able to observe holes in longitudinal fractures of bones; and I therefore infer that there are no transverse pores.

These capillary pores are seen in the flat bones of the scull. I find them in the compact matter of the outer and inner tables of the occipital bone when well burnt, in which they seem to pass gradually from the lattice-work of the diploe to the distinct pores of the tables. I doubt, however, whether these pores can be said, as in the long bones, to indicate canals. They seem rather to belong to a very delicate cancellated structure. The pores are most numerous and distinct in the bones of young subjects.

Though these circular pores are most distinct in calcined bones, and might therefore be thought to be the result of the burning, yet that they are not, I infer from the circumstance that they are seen by a good glass in the transverse fracture of splinters of the femur and other large bones.

If a portion of bone be immersed in sulphuric, nitric, muriatic, or acetic acid properly diluted, it becomes soft and pliable, and when dried, is found to be lighter than before; yet it is impossible to discover that any particle of its substance has been removed, or that its mechanical shape and appearance are changed.

If a portion of bone be placed in a charcoal fire, and the heat be gradually raised to whiteness, it burns first with flame, and at length becomes quite red. If then it be removed carefully and slowly cooled, it appears as white as chalk, is found to be very brittle, and to have lost something of its weight. Yet neither in this case does any part of its substance appear to be removed, nor is its mechanical figure or appearance altered.

Chemical examination, however, informs us that in the first case a portion of earthy matter (phosphate of lime) is removed by the agency of the acid, and held suspended in the fluid, while the pliant but otherwise identical piece of bone consists chiefly, if not entirely, of animal matter; and that, in the second case, this animal matter is removed by destructive decomposition, while the earthy matter is left little changed by the action of fire. Every particle of bone, therefore, however minute, consists of animal or organic, and earthy or inorganic matter, intimately united; and it is impossible to touch, with the point of the smallest needle, any part of bone which is not thus constituted. A piece of bone consists not of cartilaginous fibres varnished over, as Hérissant imagined, with earthy matter, but of a substance in which every atom consists of animal and earthy matter intimately combined.

There is therefore no ground for dividing osseous tissue into compact and spongy, as the old anatomists did; for though the middle parts of long bones are denser and heavier than their ends, or the bodies of the vertebrae, the difference consists not in chemical composition, but in mechanical arrangement. On dividing the head of a long bone, the lattice-work, or cancelli, as they are named, are formed by many minute threads of bone, crossing and interlacing with each other. But each thread is equally dense, and consists of the same quantity of animal and earthy matter, as the most solid part of the centre of the same bone. These threads, however, instead of being disposed compactly so as to take a small space, are so arranged that they occupy a large one, and present considerable bulk.

Though bone has been submitted to analysis by many eminent chemists, the results hitherto obtained cannot be said to be quite satisfactory. The most recent is that of Berzelius, who, in 100 parts of bone from the thigh of an adult, gives the following proportions: of gelatine 32∙17, blood-vessels 1T3, phosphate of lime 51∙04, carbonate of lime 11∙30, fluate of lime 2∙00, phosphate of magnesia 1∙16, hydrochlorate of soda and water 1∙20.

These results by no means agree with those obtained by Fourcroy and Vauquelin, who found neither fluoric acid nor phosphate of magnesia, but discovered oxides of iron and manganese, silica, and alumina, in bone. Sulphate of lime, which was found in the experiments of Hatchett, was shown by Berzelius to be formed during calcination. It is, however, obvious that a little more than a third part of bone consists of animal matter, which appears to be either gelatine, or a modification of that principle; and that the remainder, nearly equal to two thirds, consists of earthy matter, which is chiefly phosphoric acid combined with lime. The carbonic acid said to be united with lime may result from the decomposition of the animal matter. The other saline substances are not peculiar to bone, but, being common to it and the other animal tissues, and even the fluids, may be supposed to be derived from the blood left in the bone at the moment of death.

The animal matter of bones was at one time presumed to be cartilage; but this appears to be an assumption, derived from the superficial resemblance which it bears to this substance. It does not appear to be mere gelatine; for though this principle is obtained from bone, and bones are economically used in manufacturing glue, they do not furnish the same proportion of jelly as tendon, nor are they so useful in making soups, as was once paradoxically maintained by some chemists. It is probable that the gelatine is under a peculiar modification, or combined with some principle which is not well understood. The sulphur formed during calcination seems to show that this animal matter contains albumen. There is no fat in bones; and in the experiments in which this substance was found, it is evident that marrow had been mingled with the bones employed.

Though bones were arranged by the ancients among the bloodless organic substances, they receive a considerable proportion of this fluid, and injection shows them to be highly vascular. In early life especially these vessels are numerous; and even in the grown adult, when death takes place by strangulation or by drowning, the bones are found to be naturally well injected. In old age the vessels are less numerous, but they are larger. From the capillary vessels distributed through their substance, bones derive the pale blue or light pink colour by which the healthy bone is characterized. When this tint becomes intense, it indicates inflammation or some morbid state of the vessels of the bone. When it is lost, and the bone assumes a white or yellow colour, the part so changed is dead.

Anatomists distinguish three orders of vessels which enter the substance of bones; the first, those which penetrate the bodies of long bones to the medullary cavity (arteriae nutritiae, arteriae medullares) ; the second, those which go to the cellular structure of the bone; and the third, those which go to the compact or dense matter of the bone. The view is only partially correct. The large vessels termed nutritious certainly proceed chiefly to the cavity of the bone, and are distributed in the medullary membrane. These, however, are not the only vessels which proceed to this part of the bone. First, I have often traced several large vessels, entering not by the middle, but the ends of the long bones, into the loose cancellated texture, and actually distributed on the medulla in this part of the bone. In dried bones also the canals of these vessels may be demonstrated, extending from the surface to the body of the bone. Secondly, the nutritious vessels are not constant; and when they are wanting, those of the ends of the bone, or of the cancelli, are much larger and more numerous than in ordinary circumstances.
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The communication between these and the branches of the nutritious vessels, which is admitted by Bichat, may be easily demonstrated. The third order of vessels are those which may be termed periosteal, in so far as they consist of an infinite number of minute capillaries, some red, some colourless, proceeding from the periosteum to the bone, and contributing to maintain the connection between the two. The short bones and the flat bones, which are destitute of nutritious arteries, receive blood from the two latter orders, but principally from the periosteal vessels. In the scull these vessels are often highly injected in apoplectic subjects, and in persons killed by drowning or strangulation.

The veins of bones are peculiar in their arrangement. The nutritious artery is accompanied by a social vein; the articular and periosteal vessels are said to be destitute of corresponding venous vessels. According to Dupuytren, however, minute venous capillaries arise from the substance of the osseous tissue, precisely as in other tissues, and, uniting in the same manner, form twigs, branches, and trunks, which finally terminate in the neighbouring veins. Lymphatics are not found in bones, nor have nerves been traced into their substance.

To complete the anatomical history of bone, it is requisite to examine shortly the marrow. The interior of the long bones contains a quantity of fat, oleaginous matter, which has been long known under the name of marrow (μυskος οgrirnς, medulla) ; and a similar substance, though in smaller quantity, is found in the loose cancellated tissue of the flat and short bones. It is in the first situation only that it is possible to examine the anatomical characters of this substance. It is sufficiently similar to fat or animal oil in other parts of the body, to lead us to refer it to that head. In other respects its chemical qualities have not been much examined; but an analysis by Berzelius shows that it consists chiefly of an oily matter, not unlike butter in general properties. The filaments, blood-vessels, albumen, gelatine, and osmazome found by this chemist in marrow, and which did not exceed 4 parts in the 100, are derived from the filamentous tissue, in which the medullary particles are deposited.

The medullary membrane, which has been considered as an internal periosteum, is imperfectly known. There can be no doubt, however, of its existence, which is demonstrated by opening transversely or longitudinally the medullary canal of a long bone, and boiling it for about two hours. The marrow then drops out; and it will be found to be deposited in the interstices of a filamentous net-work of animal matter, like fine cellular tissue, which may be traced not only into the lattice-work of the extremities, but into the longitudinal canals of the cylindrical bones. It is traversed by blood-vessels, which are observed to bleed during amputation. No nerves have been found in it. The medullary membrane, in short, may be regarded as an extensive net-work of very minute capillaries united by delicate filamentous tissue. From these capillaries the marrow is deposited as a secretion. (Maseagni, Howship.)

3. The progressive formation of the osseous system has given rise to many researches by Kerckringius, Vater, Baster, Duhamel, Nesbitt, Haller, Dethlecf, Reichel, Albinus, John Hunter, Scarpa, Senff, Troja, Meckel, Howship, Medici, Serres, Lebel, Schultze, Bedard, and Dutrochet; and it is a proof of the complicated nature of the subject, that it continues to give rise to fresh investigation. The inquiry resolves itself into two parts,—the history of the process of ossification as it takes place originally in the foetus and infant, and the history of its progress as a process of repairwhen bones are divided,broken, or otherwise destroyed or removed.

From the first formation of the embryo to the termination of foetal existence, and thenceforth to the completion of growth, the bones undergo changes in which various stages may be distinguished. In the first weeks of foetal existence it is impossible to recognise any thing like bone; and the points in which the bones are afterwards to be developed consist of a soft homogeneous mass of animal matter, which has been designated under the general name of mucus. Some time between the fifth and the seventh week, in the situation of the extremities, may be recognised dark opaque spots, which are firmer and more solid than the surrounding animal matter. About the eighth week, the extremities maybe seen to consist of their component parts, in the centre of each of which is a cylindrical piece of bony matter. Dark solid specks are also seen in the spine, corresponding to the bodies of the vertebrae; and even the rudiments of spinous processes are observed in the shape of minute dark points. In the hands and feet rings of bone are seen in the site of the metacarpal and metatarsal bones. All the joints consist of a semi-consistent jelly-like matter, liberally supplied by blood-vessels. At ten weeks the cylinders and rings are increased in length, and arc observed to approach the jelly-like extremities, which are acquiring the consistence of cartilage, and when divided present irregular cavities. At the same time the parts forming the bead are highly vascular; and between the membranes are deposited minute points of bony matter, proceeding in rays from a centre, which, however, is thinner and more transparent than the margin. (Howship.)

Between thirteen weeks and four months the cavities in the jelly-like cartilaginous matter receive injection. The membranes of the head are highly vascular, transmitting their vessels through the intervals of the osseous rays, which are occupied abundantly by stiff, glairy, colourless, mucilaginous fluid.

In the seventh month the bony cylinder of the thighbone and its epiphyses contain canals perceptible to the microscope. In the head the bones are proceeding to completion; the pericranium and dura mater are highly vascular; and a quantity of reddish semitransparent jelly between the scalp and the scull, which contain numerous minute vessels, Mr Howship regards as the loose cellular state of the foetal pericranium. This is, however, doubtful. The cylindrical bones have at this period no medullary cavity, but present in their interior a loose bony texture.

Between the seventh and eighth months, in a foetus ten inches long, the humerus consists of a cylinder of bone placed between two brownish, firm, jelly-like masses, which correspond to the epiphyses, inclosed by periosteum, which adheres loosely by means of filamentous and vascular productions. The radius is a thin bony rod, alsobetween two jelly-like epiphyses. The ulna is still thinner, more slender and flexible, and even compressible. The interosseous ligament is a continuous duplicature of the periosteum. The metacarpal bones are much as before, only larger. The hands and fingers are complete; but the phalanges consist of minute semi-hard grains, inclosed in periosteum, which forms a general sac to them, and to the intermediate connecting parts. The middle and unguinal phalanges can scarcely be called osseous. The femur, like the humerus, is an osseous cylinder between two jelly-like epiphyses, enveloped in loosely adhering periosteum. The tibia and fibula are like the radius and ulna. The metatarsal bones are cylindrical pieces, firm, but not very hard. The first phalanx of the toes is complete; the other two, though the toes are fully formed, are much of the consist[7:2:745]ence of cartilage. The carpal and tarsal bones are in the state of the epiphyses, but of a gray colour.

In this state of the osseous system, the periosteum, which is continuous, and appears to make one membrane with the capsular ligaments and the deep-seated portions of the fascia, adheres to the bone chiefly by arteries and filamentous productions; and so loose is this connection, that a probe may be inserted beneath it, and carried round or inwards, unless where these connections are situate. Another point where the periosteum adheres firmly is at muscular insertions, to the humerus at the insertion of the deltoid, and to the femur at that of the glutaeus.

In the vertebral column the bodies of the vertebrae and the spinous plates are formed; and minute specks are beginning in the site of the transverse processes.

In the scull the parietal bones are well-formed shells of bone, though very deficient at the mesial plane, the anterior margin, and the upper anterior angle. The pericranium is distinctly membranous and vascular; and the red jelly-like fluid noticed by Mr Howship is exterior to this membrane.

At the period of birth the cylindrical bones contain tubular canals filled with a colourless glairy fluid, and terminating in the surface of ossification. As the bones previous to this period are homogeneous, and contain no distinct medullary cavity, but present in their interior a soft or loose bony texture, it is reasonable to suppose that the developement of the longitudinal canals is connected with the formation of the medullary cavity. At birth in doe femur may be distinguished a medullary cavity beginning to be formed, about half a line broad, but still very imperfect.

After birth the two processes of the formation of tubular canals and medullary cavity go on simultaneously; and at the same rate nearly the outer part of the cylindrical bones acquires a more dense and compact appearance. The epiphyses, also, which are in the shape of grayish jelly-like masses, begin to present grains and points of bone. Previously to this, Mr Howship represents them, while still cartilaginous, as penetrated by canals or tubes, which gradually disappear as ossification proceeds. The carpal and tarsal bones appear to observe the same course in the process of ossification.

In the bones of the scull, however, a different law is observed. The osseous matter is originally deposited in linear tracts or fibres, radiating or diverging from certain points termed centres of ossification. Each bone is completed in one shell without diploe or distinguishable table. Afterwards, when they are completed laterally, or in the radiating direction, the cancellated arrangement of the diploe begins to take place apparently in the same manner in which the medullary cavity and compact parts of the long bones are formed.

In the process now described, it is important to observe that the bony matter is deposited round the soft parts, and that the cavities, holes, and canals of bones are merely parts in which the previous existence of vessels, nerves, ligaments or tendons, prevents the subsequent formation of bone.

It has been generally supposed that the formation of cartilage is a preliminary step to that of bone. This, however, seems to be a mistake, arising from the circumstance that cartilage is often observed to be converted in the living body into bone. Neither in the long nor in the flat bones is any thing like cartilage at any time observed. The epiphyses, indeed, present something of the consistence of cartilage, but it has neither the firmness nor the elasticity of that substance. It is a concrete jelly, afterwards to be penetrated by calcareous matter. The flat bones are from the first osseous; and though their margins are soft and flexible, in consequence of their recent formation and moist state, they have still a distinct osseous appearance and arrangement, and bear no resemblance to cartilage. In short, true bone seems never at any period of its growth to be cartilaginous.

The progressive growth of bones is effected by accretion of new matter to their extremities. The cylindrical bones elongate by the addition of new matter to the extremities of their diaphyses, and the flat bones by the enlargement of their margins. The latter fact is established by simple inspection during the process of ossification of the cranial bones. In proof of the former, the experiment of John Hunter is decisive. In the tibia of a pig he bored two holes, one near the upper, the other near the lower end, with an interval of two inches exactly, and inserted into each hole a small leaden shot. After some time, when the animal had grown, and the length of the bone was increased, on killing it, the space between the leaden shots was found, as at first, to be exactly two inches,—thereby showing that no elongation had taken place between the perforations. The experiment was often repeated with the same result.

The period at which ossification is completed varies in different individuals. It may be said to be indicated by the completion of the medullary canal, by the ossification of the epiphyses, and their perfect union with the osseous cylinder (diaphysis). The first circumstance is indefinite. The two latter, though more fixed, are still liable to great variation. The epiphyses are rarely united before the age of 14 or 15; and they may continue detached to the 20th or 21st year. In general, however, they begin to unite or to be knit, as is said, between the 15th and 20th years.

That the main agents of original ossification are the periosteum and its arteries, the proofs are manifest. The formation of bone can be ascribed to the vessels of two agents only,—the periosteum and the medullary membrane. That the latter is not concerned in the production of bone in the foetus, must be inferred from the fact that at that period it cannot be said to exist. To the periosteum, therefore, and its vessels must be ascribed the process of foetal ossification. Of this a cumulative proof is found in the circumstance, that the periosteum adheres more firmly at the ends than the middle of the bones; and that the pericranium and dura mater, which perform the part of periosteum to the bones of the scull, are visibly concerned in the formation and successive enlargement of these bones. But though the periosteal vessels are the main agents of ossification originally, there is reason to behove that the medullary vessels contribute to its growth and nutrition after it is formed. This may be inferred from the phenomena of fractures, of diseases of the bones, and of those experiments, in which the medullary membrane is injured. The periosteum, however, does not act by ossification of its inner layers, as Duhamel, misled by a false analogy between the growth of trees and bones, laboured to establish.

A peculiar form of the osseous system requiring notice are the sesamoid bones. These, which derive their name from their minuteness, (tfn0∙α∕χj3, a grain), most of them, excepting the knee-pan, being of the size of a grain or pea, are confined to the extremities, and are situate chiefly in positions in which they give points of support to the tendons of the flexor muscles. (Tendons of the gemelli, tibialis posticus, peronoeus longus, &c.) The peculiarity of these bones is, that they are formed invariably in the substance of fibrous organs, as tendons in the case of the knee-pan and the sesamoid bones of the gemelli, tibialis posticus, and peronoeus longus ; or ligaments'
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in the case of those situate between the chiro-phalangeal and podo-phalangeal articulations. With this peculiarity their mode of ossification corresponds. At first albuminous or fibro-albuminous, in process of time they are penetrated by calcareous matter, and present an osseous texture, which, however, is much less firm than that of genuine bone. The period at which this deposition commences and is completed varies in different individuals; and hence scarcely in any two persons of the Same age is the number of sesamoid bones the same. „Though the patella may be ossified at the 20th year, the minute sesamoid bones are sometimes not formed before the 30th or even the 40th. In the patella, when ossified, we find a medullary organ; but it is uncertain whether the others acquire this mark of osseous character. These bones resemble the epiphyses in uniting, when divided, by fibro-albuminous matter.

4. The bones of which the skeleton consists are united in two modes; Isŕ, by movable junction (diarthrosis) ; 2dly, by immovable junction (synarthrosis). Both modes of union bear the general name of articulation, though this term would with greater propriety be confined to the first or movable union. By. this are connected all the bones concerned in locomotion, and some of those devoted to the organic functions, as the ribs and the lower jaw. The second is employed in the union of bones forming the walls of cavities.

In the movable union, the articular surfaces are united in two modes. In the first, in which one bone moves on the other with different degrees of freedom, the articular surfaces are covered by cartilage and synovial membrane, and the bones are united by ligaments and tendons. In the second (amphiarthrosis), in which the motion is confined to a species of torsion or imperfect rotation, the bones are united without articular surface by fibro-cartilage. The first is exemplified in the articulations of the extremities; the second is seen in the union of the bodies of the vertebrae and the bones of the pelvis.

The several forms of movable union with free motion, or articulations proper, may be referred to four heads, according to the nature of the motions performed. The first is the motion of radio-central opposition, or pivot-motion in every direction, in which the bone moves in its articular cavity, not only backwards and forwards, or by flexion and extension, but by abduction and adduction, and, by the succession of these motions, may describe a cone with the apex at the joint, or what is termed circumduction. This most extensive form of motion is found in the scapulohumeral and coxo-femoral articulations only. The second form of articular motion is antero-posterior opposition, or cardinal motion (cardo, a hinge), in which the bones move on each other by flexion and extension, as a gate on its hinges. This, which is sometimes named limited opposition, is found in the fémoro-tibial and humero-cubital joints, and all those which undergo flexion and extension. The third form of motion is that of rotation, in which the bone revolves on its axis,—an infrequent variety, confined chiefly to the humerus and femur. The fourth, which is the gliding motion, though common to all articular surfaces, is nevertheless the peculiar motion of the carpal and tarsal bones.

In the immovable union the surfaces are united in three modes. The first is by mutual indentation, or what is named suture (sutura vera), in which the margin of one bone is dovetailed by alternate serrated teeth and notches, into that of another. The second is by juxtaposition (harmonia), in which the margin of one bone is simply fitted to that of another. A peculiar variety of this is, when the acute margin of one bone is received between the biful margin of another, as the azygos process of the sphenoid bone is received by the plates of the vomer ; (schindylesis.) The third mode of immovable union is by implantation or insertion (gomphosis), as the teeth are inserted into the alveolar cavities of the superior and inferior maxillary bones.

The following table exhibits a view of these modes of junction, with their appropriate appellations.
[table]

Every tooth consists of two hard parts; one external, white, uniform, somewhat like ivory; the other internal, similar to the compact structure of bone.

The first, which is named enamel, is seen only at the crown of the tooth,· the upper and outer part of which consists of this substance. It is white, very close in texture, perfectly uniform and homogeneous, yet presenting a fibrous arrangement. Extending across the summit of the tooth in the manner of an incrustation, it is thick above, and diminishes gradually to the root, where it disappears. This fact is demonstrated by macerating a tooth in dilute nitric acid, when the bony root becomes yellow, while the crown remains white.

The enamel is not injectible, and is therefore believed to be inorganic. It is also filed and broken without being reproduced; nor does it present any of the usual properties which distinguish organized bodies. The piercing sensation which is communicated through the tooth from the impression of acids seems to depend on the mere chemical operation, and not on the physiological effect. On [7:2:747]the whole, the enamel is to be viewed as the inorganic result of a process of secretion or deposition.

The bony part of the tooth is the root and that internal part which is covered on the sides and above by the enamel. It consists of close-grained bony matter, as dense as the compact walls of the long bones, or the petrous portion of the temporal bone. The fibres which are said to be seen in it are exactly of the same nature as those in bone.

In the interior of the bony part of each tooth is a cavity which descends into the root, and communicates at its extremity with the outer surface by openings corresponding with the number of branches into which the root is divided. This cavity, which is large in young or newly formed teeth, and small in those which are old, contains a delicate vascular membrane, which has been named the pulp of the tooth. It is best seen by breaking a recent tooth by a smart blow with a hammer, when the soft pulpy membrane may be picked out of the fragments by the forceps. It then appears to be a membranous web with two surfaces, an exterior adhering to the bony surface of the dental cavity by minute vessels; the other interior, free, and, so far as can be determined of a body so minute, resembling a closed sac.

The developement and growth of the teeth is a process of much interest.

At what time the first rudiments of teeth appear seems not to be determined with accuracy. In the foetus, between the seventh and eighth month, I can merely distinguish in the centre of the vascular membrane of the alveolar cavity a minute firm body like a seed. I have, however, seen the crowns of teeth formed in foetuses which, I have reason to believe, had not attained the seventh month. But whatever may be the exact period, the process is nearly as follows.

While the bones of the upper and lower jaw are in the process of formation between the third and fourth months, (fourth and fifth, Bichat, tom. iii. p. 93,) a series of soft, membranous, vascular sacs inclosed within the general cavity of the periosteum, may be recognised at their lower and upper margins, which are still without those osseous plates which afterwards constitute the al-veoH. Each of the sacs now mentioned consists, like a serous membrane, of two divisions,—one external, attached to the periosteum, the other folded within it, and forming a closed cavity. The outer or periosteal deposits in the intervals between each sac, bone, which eventually constitutes the transverse septa of the alveoli. From the inside of the inflected portion the process of dentition commences some time between the fifth and seventh month, by the deposition of matter from the vessels at the lowest point of the alveolar division of the sac. This matter is to constitute the crown of the tooth, which is invariably formed first. After the deposition of the first portions, these are pushed upwards by the addition of successive layers below them, and necessarily carry the inflected part of the sac before them. As this process of deposition advances, the tooth gradually fills the sac, and rises till it reaches the level of the alveolar margins. If a tooth be examined in situ, near the period of birth, it is found to consist of the CTθwn, with portions of enamel descending on every side, and forming a cavity in which a cluster of blood-vessels proceeding from the sac is lodged. In the mean time, bone is deposited from the periosteal division all round each sac, so as to form the alveoli.

After the enamel has been deposited the bone begins to be formed; and as this process advances, the tooth is still forcibly thrust upwards by the addition of matter to its root. When the latter is well completed, the vessels become smaller and less abundant, until, when the tooth is perfect, they shrink to a mere membrane, which lines the cavity of the tooth, and still maintains its original connection with the alveolar membrane, by the minute vascular production which enters the orifice or orifices of the root.

Physiological authors have thought it important to mark the period at which the teeth appear at the gums; and in general this takes place about the sixth or seventh month after birth. This mode of viewing the process of dentition, however, gives rise to numberless mistakes on the period of teething. The process, as we see, commences in the early period of foetal existence; and the time at which they appear above the gums varies according to the progress made in the womb. In some the process is rapid, in others it is tardy; and even the stories of Richard III. and Louis XIV. receive confirmation from the fact of 19 examples cited by Haller, of infants born with one or more teeth above the gum. Generally speaking, the crown is completed at the period of birth; and, according as the formation of the root advances with rapidity or slowly, dentition is early or late.

What is here described is the process of the formation of the first or temporary set of teeth, which consist, it is well known, of twenty. In that of the second set the same course is observed. In the same manner is observed a row of follicular sacs, though not exactly in the original alveoli, yet attached to the sacs of the temporary teeth by vascular membranes; in the same manner deposition begins at the bottom of the free surface of the sac by the formation of the crown; and in the same manner the crown is forcibly raised by the successive accretion of new matter to its base. The moment this process commences, a new train of phenomena takes place with the primary teeth. The follicular sacs of the new or permanent teeth are liberally supplied with vessels for the purpose of nutrition; and as. these blood-vessels increase in size, those of the temporary teeth diminish; and the supply of blood being thus cut off, the latter undergo a sort of natural death. The roots which, as being last formed, are not unfrequently incomplete, now undergo a process of absorption; and the tooth drops out in consequence of the destruction of its nutritious vessels. Some authors have ascribed this expulsion to pressure, exercised by the new tooth. They forget, however, that before the new tooth can exert any pressure, it must be in some degree formed; and to this a vascular system is indispensable.

The increased number of the teeth when permanent, the enlargement of the jaws, and the consequent expansion of the face, though interesting, are foreign to the present inquiry.

Gristle, Cartilage. (Cartilago, —Tissu Cartilagineux.)

The cartilaginous system or tissue is found at least in three different situations of the human body; 1st, on the articular extremities of the movable bones; 2d , on the connecting surfaces or margins of immovable bones; 3d, in the parietes of certain cavities, the motions and uses of which require bodies of this elastic substance.

The organization of gristle is obscure and indistinct. On examination by the microscope, its surface is pearl-white, uniform and homogeneous, firm and glistening, with numerous minute pores. William Hunter represents the articular cartilages as consisting of longitudinal and transverse fibres. (Phil. Trans, vol. xlii.) Hérissant represents those of the ribs as composed of minute fibres mutually aggregated into bundles connected by short slips, and twisted in a spiral or serpentine direction. (Mém. de l’Acad. 1748.) By Delasone, the articular cartilages [7:2:748]are Said to consist of a multitude of minute threads, mutually connected and placed at right angles to the plane of the bone, but so as to radiate from the centre to the circumference. (Ibid. 1752.) The general fact of fibrous structure is confirmed by Bichat, who states that it is possible to recognise longitudinal fibres, which are intersected by others, oblique or transverse, but without determinate order. In its purest form no blood-vessels are seen in it, nor can they be demonstrated by the finest injections. In the margins of those pieces of gristle, however, which are attached to the extremities of growing bones, blood-vessels of considerable size may often be seen, even without the aid of injection. In young subjects a net-work of arteries and veins, which is described by Hunter under the name of circulus articuli vasculosus, may be demonstrated all round the margin of the cartilage at the line between the epiphysis and it. They terminate so abruptly, however, that they cannot be traced into the substance of the latter. The most certain proofs, however, of the organic structure of this substance are the serous exudation which appears in a few seconds on the surface of a piece of cartilage after division by the knife; and the fact that it becomes yellow during jaundice, and derives colour from substances found in the blood. Neither absorbents nor nerves have been found in it. The cellular texture said by Bichat to form the mould for the proper cartilaginous matter appears to be imaginary.

The articular cartilages adhere to the epiphyses by one surface, which consists of short perpendicular fibres placed parallel to each other, and forming a structure like the pile of velvet. This is easily demonstrated by maceration, first in nitric acid, and then in water. The free or smooth surface is covered by a thin fold of synovial membrane, which comes off in pieces during maceration. The existence of this, though recently denied by Gordon, was admitted by William Hunter, and may be demonstrated either by boiling, maceration, or the phenomena of inflammation, under which it is sensibly thickened. All other cartilages are enveloped, unless where they are attached to bones, by a fibrous membrane, which has been therefore named perichondrium. The existence of this may be demonstrated by dissection, and also by boiling, which makes it peel off in crisped flakes.

The chemical properties of cartilage have not been accurately examined. Boiling shows that it contains gelatine; but as much of the matter is undissolved, it may be inferred that it is under some modification, or united with some other principle, perhaps albumen. Immersion in nitric acid or boiling fluids induces crispation, and it dries hard and semitransparent like horn.

Fibro-Cartìlage, Chondro-Desmoid Texture. (Cartilago Fibrosa, — Tissu Fibro- Cartilagineux.)

Intermediate between the cartilaginous and the fibrous tissues, Bichat ranks that of the fibro-cartilages, which comprehends three subdivisions: Is/, the membranous fibro-cartilages, as those of the ears, nose, windpipe, eyelids, &c.; 2d , the inter-articular fibro-cartilages, as those found in the temporo-maxillary and fémoro-tibial articulations, the intervertebral substances, and the cartilaginous bodies uniting the bones of the pelvis; 3d , certain portions of the periosteum, in which, when a tendinous sheath is formed, the peculiar nature of the fibrous system disappears, and is succeeded by a substance belonging to the order of fibro-cartilages.

Bedard follows Meckel in rejecting the first subdivision, the individuals of which are quite similar to ordinary cartilage, in wanting the distinct fibrous structure, and being covered by perichondrium, the fibres of which have caused them to be regarded as fibro-cartilages. On this principle Bedard gives the following view of the fibro-cartilages.

1st, Fibro-cartilages free at both surfaces; those in the form of menisci, which are placed between the articular surfaces of two bones (fibro-cartilagines inter-articulares). These are seen in the temporo-maxillary, sterno-clavicdar, and fémoro-tibial articulations, and occasionally in the acromio-clavicular and the ulno-carpal joints. These ligaments are attached either by their margins or their extremities, and are enveloped in a thin fold of synovial membrane. 2d , Fibro-cartilages attached by one surface. Of this description are those employed as pulleys or grooves for the easy motion of tendons; for instance, the chondro-desmoid eminences attached to the margin of the glenoid cavity for the long head of the biceps, and at the sinuosity of the ischium for the tendons of the obturatores. 3d, Fibro-cartilages, which establish a connection between bones susceptible of little individual motion, as the intervertebral bodies; or which unite bones intended to remain fixed, unless under very peculiar circumstances, as those which form the junction of the pelvic bones. (Symphysis pubis ; sacro-iliac synchondrosis.)

The peculiarities of these substances consist in their partaking in different proportions of the nature of cartilage and white fibrous tissue, and, consequently, in possessing the toughness and resistance of the latter with the elasticity and flexibility of -the former. The structure of the fibro-cartilaginous tissue is easily seen in the intervertebral bodies, and in the cartilages uniting the pelvic bones. In the former, white concentric layers, consisting of circular fibres placed in juxtaposition, constitute the outer part, while the interior contains a semifluid jelly. The concentric fibrous layers are cartilage in a fibrous shape. In the latter situation the fibrous structure is equally distinct, while the cartilaginous consistence shows the connection with that organic substance. A similar arrangement is remarked in the inter-articular cartilage of the temporo-maxillary articulation, and in the semilunar cartilages of the knee-joint. In all, the fibrous is said to predominate over the cartilaginous structure. Their physical properties are distensibility and elasticity. Though they are at all times subjected to considerable pressure, they speedily recover their former size. Though their chemical composition is not exactly known, they evidently contain much gelatine.

Gland. Glandular System. (Glandidae.)

The name gland, though rather vaguely used, may be properly restricted to designate organs of a definite structure, consisting of arteries, veins, and excretory tubes, arranged in a peculiar manner, and destined to separate from the blood a fluid of peculiar chemical and physiological properties. The organs of this description may be arranged in two general divisions,—the follicular glands, or those which occur in an isolated form; and the conglomerate glands, or those which, being of larger volume, are understood to consist of numerous small glands combined in one general organ. The former embraces the sebaceous glands of the skin and the muciparous glands of mucous membranes; in the latter are comprehended the lacrymal and salivary glands, with the tonsils, the pancreas, the liver, the kidneys, the testicles of the male, and mammae of the female, and perhaps the prostate gland. To a third head, denominated that of imperfect glands, Meckel refers such organs as the thymus, the suprarenal capsules, the thyroid, and the spleen. But since the term imperfect implies here a contradiction, and since it is by no means ascer-tained, [7:2:749]either that these organs secrete, or that their secretions are removed by the lymphatics, it is manifest that they cannot be justly associated with the organs above defined as examples of glands.

The follicular glands, though most minute, are nevertheless distinguished by the most simple and intelligible structure. They consist of small hollow spherical sacs, or minute membranes moulded into the saccular form, in the attached surface of which are distributed numerous minute arteries and veins, and the free surface of which is smooth and covered with the fluid secreted. The quantity of vascular substance with filamentous tissue surrounding the attached surface of these glands, makes them occasionally project from the surface of the membrane to which they arc attached. In ordinary circumstances, however, they cause no elevation, and appear in the form of simple sacs with a narrow orifice. These glands belong to two textures only of the animal body,— the skin and the mucous membrane. In the former they are named sebaceous glands, from the fluid which they secrete containing a small portion of fatty matter. In the latter they are named follicles, crypts, or muciparous glands.

In certain regions of the mucous membranes, for instance in the male urethra, the crypts are arranged in such a manner that they constitute large sinuous cavities, the free surface of which secretes serous mucus copiously. These cavities, which have the further effect of increasing much the superficial extent of the membrane, are denominated lacunoe. The peculiarity of this form of mucous gland appears to consist in its membranous sac having unusual extent, and consequently in the glandular vessels being more expanded than in the ordinary glands.

The structure of the conglomerate glands is more complicated. Each gland consists of numerous minute portions of definite figure, named lobules; and each lobule may be resolved into granules, also of definite shape, intimately connected by filamentous tissue. These granules, which have since the time of Malpighi been denominated acini, are found to consist of clusters of minute arteries and veins aggregated together, with minute tubes for conveying away the secreted fluid. On these points anatomists are agreed. They arc seen most distinctly in the liver and kidney, and may be demonstrated in the pancreas, testicles, and female breast, by injection. Every acinus, in short, may be said to consist of two parts, a vascular or supplying, and a tubular or excreting.

On the manner in which these two parts of the acinus communicate, however, there is less certainty and precision. In this difficulty, as the point is scarcely a matter of observation, conjecture has been resorted to; and the opinions of anatomists have been divided between two parties. According to one, at the head of which may be placed Iluysch, Haller, William Hunter, and Hewson, the minute arteries terminate directly in the excretory ducts, without intermediate substance. According to the other opinion, which is that of Malpighi, between the arteries and the excretory tubes there are placed minute membranous vesiculae or pouches, in the substance of which the arteries, still more minutely divided, are distributed, and from the free surface of which the process of secretion goes on. In short, each acinus, according to Malpighi, is a separate follicle, and the conglomerate glands consist merely of numerous follicles, combined so as to form a large general secreting organ.

Between these two views of the intimate nature of the glandular tissue there is less difference than at first sight might be imagined. The chief difference is in the ultimate arrangement of the glandular capillaries. According to the view of Malpighi, these capillaries are arranged in clusters, as it were, round the beginning of the excretory pore, so that even in this condition the termination of the former class of vessels is the commencement of the latter. Conversely, it may be said, that since the delicate membrane in which the secreted fluid first appears necessarily receives the capillary terminations, the latter cannot be said to communicate directly with the excretory tubes. The correct view of the matter is, that by the term vesicles are not to be understood large sacs, but merely the rounded recess of the membrane which forms the excretory tubes. Further, since the researches of Hewson and Monro show that in the kidney and the testicle the arteries are convoluted, it may be inferred that this is the character of the capillary arrangement of the glands; and that it is requisite to the performance of the process of secretion that the vessels be disposed in such a tortuous manner as to prevent too rapid motion of the blood.

The conglomerate glands, we have seen, consist chiefly of minute vascular ramifications infinitely subdivided. In all the glands, excepting the liver, these vessels consist of arteries to convey blood to the organ, and veins to return it to the system; and in all the glands, excepting the liver, it is a peculiar circumstance that the same arterial trunk conveys blood for nourishing the gland, and for supplying the materials of the secretion. All the secretions, therefore, excepting that of the liver, are derived from arterial blood. The liver alone, besides receiving a considerable artery, derived from the coeliac trunk, is remarkable for being chiefly supplied with blood from a large venous trunk, formed by the union of the veins of the stomach and spleen, and the mesenteric and mesocolic branches, and which after this union is again subdivided into ramifications in the substance of the gland. Injection shows that the branches and twigs of this vein anastomose freely with those of the hepatic artery; and though it might be imagined that the latter is intended chiefly to nourish the gland, and the former to supply the materials for secretion, this circumstance, with the fact that in some rare instances the vena portae is not distributed in the liver, shows that at present this opinion must be adopted with caution.

Besides arteries, veins, and excretory tubes, glands are supplied with lymphatic vessels, which are arranged in two sets, superficial and deep. The former are confined to the surface of the organ, over which they may be seen creeping in every direction, and belong chiefly to the membranous coverings of the glands. The deep-seated lymphatics are those which penetrate the substance of the glands, and in general accompany the large bloodvessels.

Every gland receives a proportion of nervous branches, genera!ly from the nerves of the sympathetic system. These branches accompany the blood-vessels in penetrating the substance of the glands, and are distributed much in the same manner as the arteries before their ultimate division. They exercise some influence over the process of secretion; but the nature and extent of this influence are still undetermined.

Each gland contains a quantity of filamentous tissue, which envelopes the blood-vessels, tubes, lymphatics, and nerves, and constitutes a large proportion of the mass of the gland. The simple tissues, thus united, are inclosed in a general membranous covering, which also partly contributes with these tissues to retain it in its situation. These membranous coverings vary in different glands. In the liver and pancreas it is the peritoneum; the kidneys are inclosed in a peculiar tunic; the testes are contained in a fibrpus membrane; and the acini of the lacrymal [7:2:750]and mammary glands appear to be covered by a form of condensed filamentous tissue.

CHAP. III. ENVELOPING TISSUES.

Skin. ( Cutis, Pellis.) Cutaneous Tissue, Dermal Tissue. (La Peau, Tissu Dermoide,— Die Haut, Das Fell.) Fell, old English; with its appendages, Scarf-shin or Cuticle, Nail, Hair. (Cuticula, Epidermis, — Tissu Epidermoide et Tissu Pileux.)

Skin has been said to consist of three parts, true skin (cutis vera), mucous net (rete mucosum), and scarf-skin or cuticle. Haller, Camper, and Blumenbach, are inclined to deny the existence of the mucous net in the skin of the white, and to admit it in that of the negro only; and in point of fact, indeed, its existence has been demonstrated in the negro race only, and inferred by analogy to exist in the white, “When a blister has been applied to the skin of a negro,” says Cruikshank, “if it has not been very stimulating, in twelve hours after a thin transparent grayish membrane is raised, under which we find a fluid. This membrane is the cuticle or scarf-skin. When this with the fluid is removed, the surface under these appears black; but if the blister had been very stimulating, another membrane, in which this black colour resides, would also have been raised with the cuticle. This is rete mucosum, which is itself double, consisting of another gray transparent membrane, and of a black web very much resembling the pigmentum nigrum of the eye. When this membrane is removed, the surface of the true skin, as has been hitherto believed, comes in view, and is white like that of a European. The rete mucosum gives the colour to the skin; is black in the negro; white, brown, or yellowish in the European.” (Experiments on the Insensible Perspiration, &c. London, 1795.)

Bichat denies the existence of a mucous varnish (corpus mucosum) such as Malpighi describes it, and regards the vascular surface of the corion as the only mucous net.

According to Chaussier the skin consists of two parts only, the derma (δiξμα, cutis vera) or corion, and the epidermis, cuticle, or scarf-skin; the first embracing the organic elements of this tissue; the second being an inorganic substance prepared by the organic, and deposited on its surface. This opinion is adopted by Gordon, according to whom the skin consists of two substances placed above each other, like layers or plates (laminoe), the inner of which is the true skin, the outer the cuticle or scarf-skin. Bedard, on the contrary, thinks that a peculiar matter, which occasions the colour by which the several races are distinguished, is found between the outer surface of the corion and the cuticle; and that no fair race is destitute of it except the albino, the peculiar appearance of whom he ascribes to the absence of the mucous net of the skin.

The corion of the human skin (pellis, corium, derma, cutis vera) seems to consist chiefly of very small dense fibres, not unlike those of the proper arterial coat, closely interwoven with each other, and more firmly compacted the nearer they are to its outer or cuticular surface. The inner surface of the corion is of a gray colour; and in almost all parts of the body presents a number of depressions varying in size from ∙⅛th to τ 1 θth of an inch, and consequently forming spaces or intervals between them. These depressions, which correspond to eminences in the subjacent adipose tissue, have been termed areolae. They are wanting in the corion of the back of the hand and foot only.

The outer or cuticular surface of the corion is smooth, of a pale or flesh-red tinge, and is much more vascular than its inner surface. It presents further a number of minute conical eminences (papillae), which, according to the recent observations of Gaultier and Dutrochet, are liberally supplied with blood-vessels, and are the most vascular part of this membrane. In the ordinary state of circulation and temperature during life these eminences are on a level with the surrounding corion ; but when the surface is chilled, this membrane shrinks, while the papillae either continue unchanged or shrink less proportionally, and give rise to the appearance described under the name of goose shin (cutis anserina). This surface was said by the older anatomists to present numerous orifices or pores; but according to Gordon, if we trust to observation, no openings of this kind can be recognised, either by the eye or the microscope, except those of the sebaceous follicles. The hairs, indeed, are found to issue from holes in the corion, but they fill them completely.

In certain situations, for instance at the entrance of the external auditory hole, at the tip of the nose, on the margins of the eyelids, in the armpits, at the nipple, at the skin of the pubes, round the anus and the female pudendum, are placed minute orifices, from which exudes an oleaginous fluid, which is quickly indurated. These openings lead into the cavities of small sacs called follicles (folliculi) or sebaceous glands (glandulae sebaceae). These sacs, the structure of which is noticed above, consist of hollow surfaces secreting an oleaginous fluid, which is progressively propelled to the orifice, where it soon undergoes that partial inspissation which gives it the sebaceous or suet-like aspect and consistence.

The corion is liberally supplied with blood-vessels, nerves, and absorbents. After a successful injection, its outer surface appears to consist of a uniform net-work of minute vessels, subdivided to an infinite degree of delicacy, and containing during life blood coloured and colourless. It can scarcely be doubted that this vascular net-work (rete vasculosum) is the only texture corresponding to the reticular body of the older anatomists.

It is well known that this membrane, when boiled sufficiently long, is converted into a viscid glutinous liquor, which consists chiefly of gelatine (Chaptal, Seguin, Hatchett, Vauquelin, &c.), and that glue is obtained from it for the purposes of art. As, however, in these operations a portion of matter is left undissolved, and as glue is completely soluble in water, while skin resists it for an indefinite time, it may be concluded, that though the chief constituent of the corion is gelatine, it is under some peculiar modification not perfectly understood. The union of this organized gelatine with the vegetable principle denominated tannin forms leather, which is insoluble in water.

Cuticle or scarf-skin (epidermis, cuticula) is a semitransparent, or rather translucent layer of thin lightcoloured matter, extended continuously over the outer surface of the corion. Its thickness varies, being thinnest in those parts least exposed to pressure and friction, but thickest in the palms and soles. It is destitute of bloodvessels, nerves, and absorbents; and there is reason to believe, from observing the phenomena of its reproduction, that it is originally secreted in the form of a semifluid viscid matter by the outer surface of the corion; and that, as it is successively worn or removed by attrition, it is in like manner replaced by a constant process of secretory deposition. This semifluid viscid matter, which in truth is found between the outer surface of the corion and the firm cuticle, is the substance mentioned by Malpighi, and so often spoken of as the mucous net (corpus mucosum). It is inorganic; and it is impossible to explain its production otherwise than by ascribing it to the outer vascular surface of the corion.
[7:2:751]

Cuticle is rendered yellow and finally dissolved by immersion in nitric acid. It is also dissolved by sulphuric acid in the form of a deep brown pulp. These, and some other experiments performed by Hatchett, show that it consists chiefly of modified albuminous matter.

This description shows, that if strict observation be trusted, the mucous net has no existence, at least in the European. In the Negro, Caffre, and Malay, however, a black membrane is said to be interposed between the corion and cuticle, and to be the cause of the dark complexion of these races. On this subject I refer to the description given by Cruikshank, which is the best (Experiments, &c. p. 31, 41, and 43); the Essay of Μ. Gaultier, already quoted; and the observations of Bedard. What is found in the skin of the mixed or half-caste races, i. e. the offspring of an African and a European, or of a mulatto and European? and how is the transition between this colouring layer and its insensible diminution effected?

Nail is a substance familiarly known. On its nature and structure we find many conjectures, but few or no facts, in the writings of anatomists; and almost all that has been written is the result of analogical inference rather than of direct observation. It is known that the nails drop off with the scarf-skin in the dead body; that they are diseased or destroyed by causes which act on the outer surface of the corion, and produce disease of the cuticle; and that, if forcibly torn out, the surface of the corion to which they were attached bleeds profusely and inflames. In other respects they are inorganic; but these facts warrant the conclusion that the root of the nail is connected with the organic substance of the corion, and that the whole substance is the result of a process of secretion similar to that by which the cuticle is formed.

According to the experiments of Hatchett, they consist of a substance which possesses the properties of coagulated albumen, with a small trace of phosphate of lime.

The root of a hair is not only that part which is contained in the bulb, but the portion which is lodged in the skin. The middle part and the point are those which project beyond the surface of the skin. The bulb is a small sac fixed in the inner surface of the corion, in the contiguous filamentous tissue, and in which the root is implanted.

Every hair is cylindrical, tapering regularly from the root to the point, and solid, but containing its proper colouring matter in its substance. The colour varies, but the root is always whitish and transparent, and softer than the rest; the fixed or adhering part of the root is almost fluid. When hair is decolorized, it becomes transparent and brittle, and presents a peculiar silvery-white colour; and as hairs of this kind are few or abundant, it gives the aspect of gray, hoary, or white hair.

The bulb, though visible in a hair plucked out by the root, is too small in human hair to be minutely examined; and Chirac, Gaultier, and Gordon, have therefore described its structure and appearances from the bulbs of the whiskers of large animals, the seal for example, in which it is much more distinct. According to researches of this kind, every bulb forms a sort of sac or follicle, which consists of two tunics, an inner one, tender, vascular, and embracing closely the root of the hair; and an outer, which is firmer and less vascular, and surrounds the inner one, while it adheres to the filamentous tissue and the inner surface of the corion. When the hair issues from the bulb, it passes through an appropriate canal of the corion, which is always more or less oblique, but which, as has been already said, it fills completely; and it afterwards passes in a similar manner through the scarf-skin. Nervous filaments have been traced into the bulbs of the whiskers of the seal by Rudolphi and the younger Andral. The bulb or follicle, in short, is organic, and forms by secretion the inorganic hair.

The structure of hair appears to be either so simple, or so incapable of being further elucidated, that anatomists have not given any facts of consequence regarding it. Its outer surface is believed to be covered with imbricated scales, because in moving a single hair between the finger and thumb it follows one direction only.

Hair is believed to be utterly inorganic, though the phcuomena of its growth, decoloration, and especially of the disease termed Polish plait (plica Polonica), have led various authors to regard it as possessed of some degree of vitality. These phenomena, however, may be explained by the occurrence of disease in the bulbs or generating follicles. Hair is insoluble in boiling water; but Vau-quelin succeeded in dissolving it by the aid of Papin’s digester. From the experiments of this chemist, and those of Hatchett, it may be inferred that hair consists of an animal matter, which appears to be a modification of albumen, a colouring oil, and some saline substances.

Mucous Membrane, Villous Membrane. (Membrana Mucosa, Μ. Mucipara, Μ. Villosa, — Tissu Muqueux, Bichat.)

The organic tissue or membrane to which the name of mucous or villous has been applied, consists of two great divisions, the gastro-pulmonary and genito-urinary.

The first or gastro-pulmonary division comprehends that membranous surface which commences at the various orifices of the face at which it is contiguous with the skin, and is continued through the lacrymal and nasal passages, and even the Eustachian tube, by the larynx on the one hand to the windpipe and bronchial membrane, and by the oesophagus on the other through the entire tract of the alimentary canal, at the opposite extremity of which it is again identified with the skin.

The distribution of the second division, or the genitourinary mucous membrane, is slightly varied according to the differences of sex. In the male it is connected with the skin at the orifice of the urethra, from which it proceeds inwards toward the bladder, sending previously small prolongations through ducts on each side of the veru montanum, from which it is believed to be continued through the vasa deferentia, to the vasa efferentia of the testicle. Continued over the inner surface of the urinary-bladder, it is prolonged through the ureters to the pelvis and infundibula of the kidney. In the female, besides passing in this direction, it ascends into the womb, and passes through the Fallopian or uterine tubes, at the upper extremity of which it terminates in an abrupt opening into the sac of the peritoneum—the only instance in the whole body in which a mucous and serous surface communicate freely and directly.

These two orders of membranous tissue have each two surfaces, an attached or adherent, and a free one. The adherent surface is attached, 1st, to muscles, as in the tongue, most of the mouth and fauces, oesophagus, and whole alimentary canal, and the bladder; 2d , to fibrous membranes, as m the nasal cavities and part of the larynx, in which it is attached to periosteum or perichondrium, the palate, ureter, and pelvis of the kidney; 3d, to fibro-cartilages, as in the windpipe (trachea), and bronchial tubes.

The free surface is not uniform or similar throughout. The appearance of the pituitary or Schneiderian mem[7:2:752]brane is different from that of the stomach or intestines; the surface of the tongue and mouth is different from that of the trachea; and the free surface of the urethra is unlike that of the bladder. These variations depend on difference of structure, and are connected with a difference in properties; yet anatomists have improperly applied to the whole what was peculiar to certain parts only, and have thus created a system in which some truth is blended with much misrepresentation.

Mucous membrane consists, like skin, of a corion or derma, and an epidermis or cuticle.

The mucous corion is a firm, dense, gray substance, which forms the ground-work of the membrane in most regions of the body, but which is evidently represented by the fibrous system, e. g. the periostemn or perichondrium, in some other situations. It is most distinctly seen in the mouth and throat, and in various parts of the alimentary canal. In the first situation it is more vascular, less gray and dense, than in the intestinal mucous membrane.

It possesses two surfaces, an inner, adherent to the submucous filamentous tissue, and an outer or proper mucous surface. In the stomach, the mucous corion is in the form of a soft but firm membranous substance, about ⅜th or ⅛th of a line thick, tough, of a dun-gray or fawn colour (intermediate between Sienna-yellow and ochre-yellow, Syme), slightly translucent, and sinking in water. The attached or inner surface is flocculent and tomentose, and a shade lighter than the outer, which presents a sort of shag or velvet, consisting of very minute piles. This, when examined by a good lens at oblique light, appears to consist of an infinite number of very minute roundish bodies closely set, but separated by equally minute linear pits, and occasionally circular depressions. In the ileum it presents much the same characters; but the minute bodies of its shaggy surface are still larger and more distinct, and may be seen by the naked eye. In the windpipe, again, it is rather thinner and lighter coloured; and while its outer surface presents numerous minute pores, it> is much smoother than in the alimentary canal, and entirely destitute of those minute bodies seen in the latter. It nowhere presents any appearance of fibres.

The mucous corion rests on a layer of filamentous tissue, firm and dense, and of a bluish-white colour,— a, character by which it is distinguished from the soft fawn-coloured mucous membrane. This submucous filamentous tissue is what is erroneously termed the nervous coat by Ruysch, Albinus, and some of the older anatomists.

In certain -parts the mucous corion is covered by a thin transparent membrane, named the epidermis or cuticle, which is most easily shown by boiling or scalding a portion of mucous membrane, and then peeling off with care the outer pellicle. This experiment succeeds best in the mucous membrane of the mouth and palate, in which, therefore, the existence of mucous epidermis cannot be doubted. The observations of Wepfer, Haller, and Nicholls, and especially of Blculand (Observationes Anato-micoMedicae de Sana et Morbosa (Esophagi Structura, Lug. Bat. 1785), are sufficient to prove its existence in the oesophagus. Bichat admits that, though it may be demonstrated at the cutaneous junctions of the mucous surfaces, it cannot be recognised in the stomach, intestines, bladder, &c. From the numerous dissections of Home (Phil. Trans. 1807, 1810, 1813), it results that the mucous epidermis, both in the human subject and in most mammalia and birds, terminates abruptly at the cardiac orifice of the stomach. In ruminant animals the mucous epidermis is continued over the first two stomachs, but cannot be traced in the third and fourth. In the whale tribe, in which the stomach is also quadruple, the epidermis is confined to the first cavity. In birds of the graz- j ing tribe, the mucous epidermis is continued over the giz-^ zard, but terminates at the opening into the stomach.ŋ This conclusion as to the human subject is confirmed by Bedard, who further adds, that in the genito-urinary system it cannot be traced beyond the neck of the womb and that of the bladder.

In most mucous membranes are found minute oval or spheroidal bodies, slightly elevated, and presenting an orifice leading to a blind or shut cavity. As they are believed to secrete a fluid analogous to or identical with mucus, they are named mucous glands; and from their shape and situation they are also denominated follicles (folliculi) and cryptae. Though more or less abundant in all the mucous membranes, they have been most frequently examined in those of the alimentary canal, where they were first accurately described by Brunner and Peyer. (Glanduloe Peyerianoe^) In this situation they are situate in the substance of the mucous corion. Their structure is simple. The orifice leads into a saccular cavity, with a smooth, uniform surface, which secretes the fluid which oozes from them. This membranous sac is lodged in a reddish-coloured, dense, anormal matter, which is probably filamentous tissue enveloping minute blood-vessels; but of the minute structure of which nothing is accurately known. In the state of health these bodies are so minute that it is very difficult to recognise them. I have seen them, nevertheless, in the tracheo-bronchial membrane by the eye and by a lens. When the membranes are inflamed they become larger and more distinct. In the bladder, the womb, the gallbladder, and the seminal vesicles, they are not distinctly seen, and cannot be satisfactorily demonstrated. It is unnecessary, however, to follow the example of Bichat in trusting to analogy to prove their existence; for they are not necessary to the secretion of mucous fluid, as he seems to imagine. Those in the urethra, first well described by William Cowper, are distinct examples of follicles in the genito-urinary surface. The sinuosities (lacunoe), first accurately described, if not discovered, by Morgagni (Adversaria Anatomica, iv. 8, 9, &c.), though not exactly the same in conformation and structure, seem to be very slightly different.

In certain regions of the mucous membranes, especially at their connections with the skin, are found minute conical eminences denominated papilloe. They are distinctly seen in the mucous membrane of the tongue, where they vary in size and shape, and in the body named clitoris. They are elevations belonging to the mucous corion, covered by epidermis, and they are liberally supplied by blood-vessels, the veins of which present an erectile arrangement, and with minute nervous filaments.

In the stomach, duodemun, and ileum, this membrane is collected into folds or plaits, which have received in the former situation the name of rugoe, or wrinkles; and in the latter the name of plicae, or folds, and valvulae conniventes, or winking valves. In the vagina also are transverse rugoe, which in like manner are folds or duplicatures of its mucous membrane. Those of the oesophagus, which have been described by Blculand, are longitudinal. In the tracheo-bronchial membrane, and in the membranous and spongy portions of the urethra, we find them in the shape of minute plaits or wrinkles in the long direction or their respective tubes, but rarely of much length. The object of these folds, which are peculiar to the mucous membranes, appears to be to increase the extent of surface, and to allow the membrane to undergo considerable occasional distension.
[7:2:753]

In certain points, where a communication is observed between the general mucous surface and the cavities or recesses of particular regions, anatomists, unable to demonstrate a mucous membrane, have inferred its existence as a continuation of the general surface. In the tympanal cavity, to which the Eustachian tube leads, the existence of a mucous or fibro-mucous membrane is rather presumed from analogy than proved by observation. We know that, where the biliary and pancreatic ducts enter the duodenum, and for a considerable space towards the liver, the interior appearance is that of a fine mucous surface provided with lacunoe and villosities; but it is impossible to say at what point of the hepatic duct, or of the smaller canals of which it is formed, the mucous membrane terminates. The tracheal membrane, when traced to the bronchial divisions, presents no arrangement, either of papilloe, piles, or villosities; and nothing is perceived except a smooth uniform surface, of a colour between gray, dun, and red or purple, which is moistened with a viscid semi-transparent fluid, and which is as like the peritoneum as the intestinal mucous membrane. Lastly, the situation where the existence of the mucous system, though believed, is most uncertain, is in the interior of the vasa deferentia, where they take their origin from the vasa efferentia of the testis. Regarding the organization of these tubes, no sensible evidence can be obtained, and whatever is stated concerning it is the result of analogical inference.

Though these membranes have been designated by the general name of mucous, the action of their surface is not in every situation the same. It is not easy to limit the signification of the term mucus ; for this fluid varies in the nasal passages, in the trachea and bronchial membrane, in the oesophagus, stomach, and intestines, and in the urinary bladder and ureters. But it may be stated that many parts of the two mucous surfaces never in the healthy state secrete any modification of this animal matter; and in others the membrane is almost always moistened by a different fluid. The mucous or villous membrane of the eyelids is never in the healthy state occupied by mucus, but is uniformly moistened with the tears; the membrane of the mouth and throat is moistened with saliva only; the urethra presents a peculiar viscid fluid, which seems to exude from many minute vessels opening along its surface, as in the lacunoe, but which is widely different from mucus. All those parts, in short, which are not in perpetual, but only occasional, contact with foreign or secreted substances, seem to present no mucus in the healthy state; whereas the surfaces of the stomach, intestines, gall-bladder, and urinary bladder, are constantly covered with a quantity, more or less considerable, of this animal secretion.

The chemical properties of mucous membranes are completely unknown. The analysis of the fluid secreted by them has been executed by Fourcroy, Berzelius, and others, but is foreign to the subject of this article.

That the mucous membranes are liberally supplied with blood by vessels both large and numerous, is proved not only by the phenomena of injections, but by the red colour of which many of their divisions are the seat. This coloration, as well as the injectibility, is not indeed uniform; for in certain regions mucous surfaces are pale or light blue, in others their redness is considerable.

Thus, in those regions in which the mucous membranes coalesce with the periosteum, forming fibro-mucous membranes, e. g. in the facial sinuses, the tympanal cavity and the mastoid cells, the colour is pale blue, or approaching to light lilac. In the bladder, in the large intestines, in the excretory ducts in general, though pale, this colouring becomes more vivid. In the pulmonic mucous membrane it is slate-blue, verging to pale pink. In the stomach, duodenum, small intestines, and the vagina, it becomes still more marked. In the uterus it varies according to the period or the intervals of menstruation.

Examined in the gastro-enteric mucous membrane, in which they are most numerous, these vessels are found to consist of an extensive net-work of capillaries divided to an infinite degree of minuteness, mutually intersecting and spreading over the upper or outer surface of the mucous corion. This vascular net-work, though demonstrated by Ruysch, Albinus, Haller, and Bichat, has been beautifully represented in the delineations of Blculand, who thinks he has traced their minute ramifications into the villi. These minute vessels are derived from larger ones, which creep through the submucous cellular tissue, and penetrate the mucous corion, the substance of which receives few or no vessels, to be finally distributed at its exterior surface.

The arrangement of the vessels which supply the mucous surfaces is peculiar. Penetrating, in the form of considerable trunks, between the folds of the serous membranes, they divide in the subserous cellular tissue into branches of considerable size; and here they form those numerous anastomotic communications which constitute the arches so distinctly seen in the ileum. From the convexity of these arches are sent off most of the small vessels, which are then fitted, after passing through the muscular layer and the submucous tissue, to enter the mucous corion.

The capillary terminations, then, of these arteries, and their corresponding veins, constitute the physical cause of the coloration of the mucous membranes. This coloration, however, is not at all times of the same intensity in the same membrane, and varies chiefly according to the state of the organ which the membrane covers. The coloration of the gastro-enteric mucous membrane undergoes, even within the limits of health, many variations. Thus, according to the absence or presence of such foreign substances as are taken at meals, the mucous membrane is pale, or presents various shades of redness. At the period of menstruation the uterine mucous membrane becomes red and injected. Pressure on any of the venous vessels renders the mucous membranes blue, purple, or livid, as is seen in prolapsus, and more distinctly in asphyxia, in which all the mucous membranes assume a livid tint. (Bichat.) The varieties of red colour observed in the gastric mucous membrane by Dr Yellowly are to be ascribed partly to the latter cause, partly to the vascular redness which the presence of foreign bodies occasions. (Medico Chirurg. Trans, vol. iv. p. 371.) The pulmonary division of this membrane is of an ash-gray or dun colour, inclining to pale blue or light red. These colours vary, nevertheless, according to the facility or the difficulty with which the blood moves through the pulmonary capillary system. It is also freely supplied with blood-vessels derived chiefly from the bronchial arteries. These vessels, after accompanying the bronchial tubes and their successive subdivisions, divide into minute branches which penetrate the mucous corion, which here is white, dense, and fibrous, and after anastomosing with the capillaries of the pulmonary artery and veins, form a minute delicate net-work on the outer surface of the pulmonary mucous membrane. According to Reisseissen, to whom we are indebted for a careful examination of these vessels, a successful injection of them from the bronchial arteries renders the whole mucous membrane of the bronchi entirely red to the unassisted eye. ( Ueber den Bau der Lungen, u. s. w. Berlin, 1822.) [7:2:754] The termination of arteries at the mucous surfaces has at all times occupied the attention of anatomists and physiologists; but it is not a matter of sensible demonstration. The thin serous or sero-mucous fluid with which they are moistened has led every author almost, and among the rest Haller and Bichat, to infer the existence of arteries with orifices, or what are termed exhalant vessels. It has been admitted, nevertheless, more on analogical than direct proofs. The injections of Blculand, the only experiments, after those of Kawe Boerhaave, which tend to confirm the conclusion, require nevertheless to be repeated and varied.^[89. Experimentum Anatomicum, quo Arteriolarum Lymphaticarum existentia probabiliter adstrιιitur, &c. a Jano Blculand, Μ. D. Lugd. Bat. 1784. Item, Jani Blculand, Μ. D. &c. Vasculorum Intestinorum tenuium Tunicis subtilioris Anatomes Opera Detegendorum Descriptio Iconibus illustrata. Trajecti, 1797· ]

That lymphatics are distributed to mucous membranes, is a point well established. Cruikshank saw the lymphatics proceeding from the pulmonic mucous membrane loaded with blood in persons and animals dying of hae-moptoe. Their existence in the gastro-enteric mucous membrane has been long established.

The mucous surfaces arc also freely supplied by nervous twigs and filaments, derived in general from the nerves of automatic life. It is a mistake, nevertheless, to ascribe to these filaments the sensibility and other properties of the mucous membranes, which possess intrinsically certain vital properties independently of the nervous filaments with which they are supplied; and the principal use of these filaments appears to be to regulate these properties, especially that of secretion.

The connection between the mucous membranes and the skin was first demonstrated by Bonn, who traces their mutual approximation and reciprocal transition into each other, and represents the former as an interior production of the latter, enveloping the internal as the skin incloses the external organs. This view has been adopted by Meckel and Beclard, to whom I refer for the proofs of its accuracy. I cannot conclude the subject, however, without observing that one of the most conclusive arguments in its favour is derived from the circumstances of the developement of the intestinal canal during the first months of uterine life. The history of this curious process, which has been investigated by Wolff, Oken, and Meckel, shows that at this period the gastro-enteric mucous membrane, which is previously formed by the vitellar membrane of the ovum, and the allantois or vesical membrane, which afterwards forms the genito-urinary mucous surface, are in direct communication on the median line, and afterwards at the navel, with the skin or exterior integument.

Serous Membrane, Transparent Membrane. (Membrana Pellucida, Μ. Serosa. —Tissu Séreux.)

The pleura and peritoneum are the best examples of the tissue which has been named serous, from the fluid with which it is moistened, and which may be termed transparent or diaphanous as its distinctive character.

The distribution or mechanical arrangement of these membranes is peculiar, and though not well understood by anatomists, till Douglas, by his description of the peritoneum, rendered it clearer, may now be said, by the labours of Hunter, Carmichael Smyth, and Bichat, to be quite intelligible. In this, nevertheless, there are certain peculiarities which may perplex the beginner, and prevent him from obtaining at first a clear idea of the distribution and configuration of the pellucid membranes. Thus they have neither beginning nor termination; they have neither orifice nor egredient canal; and they are not continuous with any other membrane or texture.

Every serous membrane consists of a hollow sac everywhere closed, and to the cavity or interior surface of which there is no natural entrance; a circumstance from which they have been denominated shut sacs (sacci occlusi ; sacs sans ouverture). In every serous membrane one part is inverted or inflected, or reflected, as is commonly said, within the other, so that the inner surface of the former part is applied with more or less accuracy to the inner or like surface of the latter. This mode of disposition has suggested the homely and trite, but not inappropriate comparison of a serous membrane to a night-cap, one half of which is folded or doubled within the other, so that while one half of the inner surface is applied to the remaining half, no communication exists between the inner and the outer surface. Every serous membrane, in short, is a single sac, one half of which is doubled within the other.

In every serous membrane the outer surface of the unreflected portion is applied over the walls of the region which the serous membrane lines, while the outer surface of the inflected portion is applied over the organ or organs contained in that region. From this arrangement it results that each organ covered by serous membrane is not contained in that membrane, but is on its exterior surface, and that of every organ so situate, one part at least, viz. that at which its vessels and nerves enter, is always uncovered. Thus the lungs are on the outer surface of the pleura; the heart is on the outside of the pericardium; the stomach, intestines, liver, spleen, and pancreas, arc on the outside of the peritoneum; and the testicles are on the outside of the perididymis. In the same manner the lungs, though invested by pleura before and behind, at their apex and their base, are uncovered at their roots, or the points where the bronchial tubes and great bloodvessels enter their substance; the heart is uncovered by pericardium at the upper part of the auricular cavities; and the intestinal canal is uncovered along the whole of that longitudinal but tortuous line by which the mesentery is attached, and at which its proper vessels and nerves are transmitted.

To comprehend more distinctly the arrangement of the pellucid membranes, it is expedient, by an effort of abstraction, to trace the course of any one of them, having previously thrown out of the question the means by which their interior free surface is exposed. In this mental process it is requisite to remember that there is no initial point save what is arbitrarily made. If, for example, the course of the pleura be traced, the membrane presents no natural boundary from which the anatomist is to commence his demonstration; and he must fix artificially on any point which he finds most convenient for the purpose. Commencing with this understanding, from the circumference of the spot termed root of the lungs, the membrane may be traced first along the internal surface of the chest formed by the ribs and intercostal muscles, forwards to the sternum, upwards to the first rib and apex of the thoracic cavity, downwards to the diaphragmatic insertions, and over the surface of that muscle, and the outer surface of the pericardium again to the circumference of the root or connection of the lungs. From this point again it may be traced over the surface and between the lobes of these organs, both of [7:2:755]which, as already stated, are thus situate on the outside of the pleura. The course first described is that of the unreflected or exterior division of the pleura. The second, or that over the organ covered, is the course of the inflected or doubled portion of the membrane, which is thus necessarily smaller, and less extensive, than the former.

The arrangement thus sketched, which may be easily shown to be applicable to all the serous membranes, demonstrates their twofold character of lining the walls of a cavity and covering the organs contained. From an idea of this property, the old anatomists applied to them the epithet of membranae succingentes.

In tracing the course of the serous membranes, the anatomist observes that they present productions which float with more or less freedom in the cavity formed by the free surface, and which may be generally shown to consist of two folds of the single membrane produced beyond the inclosed organ, but still maintaining the unity of the membrane. Of these prolongations, the most distinct examples are the epiploon and the appendices epiploicae of the peritoneum. Less manifest instances are the adipose folds of the pleura near the mediastinum, and the bladder-like appearance at the base of the heart, within the pericardium. The synovial fringes in the interior of the synovial membranes, which belong to a subsequent head, are nevertheless of the same general character. Between the folds of these productions there is invariably more or less adipose substance, which indeed is observed in some quantity in various parts of the filamentous tissue on the outer surface of the serous membranes in general.

Every serous membrane I have above represented as a hollow sac everywhere continuous, and the outer surface of which has no communication with the inner. To this character the only exception is the peritoneum in the female, which is perforated at two points, corresponding to the upper extremity or orifice of the Fallopian or oviferous tubes. This has been already mentioned as the only spot at which the mucous and serous surfaces communicate directly with each other.

Every serous membrane consists of a thin, colourless, transparent web or pellicle, through which the tissue of the subjacent organ or parts may be easily recognised; and every serous membrane presents two surfaces, an attached or adherent, and a free or unadherent.

The attached surface, which is also termed its outer one, is that by which it is connected to the tissue or organ which it covers; it is somewhat irregular, flocculent or tomentose, and is evidently connected by fine filamentous tissue. The degree of attachment is very variable in different membranes, and in different points of the same membrane. In general, serous membranes adhere much less firmly to the walls of cavities than to the surface of the contained organs. Thus, the abdominal peritoneum and the costal pleura are more easily removed than the intestinal peritoneum and the pulmonic pleura. The peritoneum adheres feebly to the bladder, to the liver, and to the pancreas—more intimately to the different regions of the intestinal tube, and seems to be almost identified with the substance of the female organs of generation. From the interior of the capsular pericardium, and from the vaginal coat, it is almost impossible to detach the serous pellicle. The former, however, is peculiar in having between the serous surface and the fibrous membrane no filamentous tissue, upon the abundance or deficiency of which the degree of adhesion depends.

The free or unadherent or inner surface is very smooth, polished, and uniform; moistened with a watery fluid, from which it derives its shining appearance; and destitute of fibres or any other trace of organic structure. From this smooth, polished aspect, which is a peculiar attribute of the free surface of serous membrane, all the organs covered by it derive their glistening appearance. Thus the exterior surface of the lungs derives its appearance from the pleura, the heart from the pericardium, and the liver and intestinal canal from the peritoneum. A successful injection of size or turpentine, coloured with vermilion, brings into view so many capillary blood-vessels in this membrane, that it might be supposed at first sight to consist entirely of minute arteries and veins. Further, by proper management, lymphatics may be injected in it with quicksilver to a degree equally minute and delicate. From these experiments, therefore, it may be concluded that serous membrane is chiefly composed of minute arteries and veins conveying colourless fluids, and of vessels connected with the general trunks of the lymphatic system. Whether it contains any thing else but vessels of this kind, or has a proper, substance or tissue, remains to be ascertained. Though nerves are often seen passing along their outer or attached surface to the neighbouring tissues, none have hitherto been traced either into the pleura or peritoneum.

By most of the older anatomists, and among others by Haller, serous membrane is considered as of the nature of filamentous tissue or cellular membrane, more or less closely condensed (tela cellulosa stipata) ; and this view is adopted and maintained by Bordeu, Bichat, Meckel, and Beclard, the last of whom, however, thinks they partake of ligamentous characters. Macerated, they become soft, thick, and pulpy; and are finally resolved into flocculent filamentous matter. In the course of decomposition in the dead subject they first lose their glistening aspect, then become covered by a foul, dirty coating of viscid matter, which appears to exude from their surface; and eventually they are dissolved into shreds. Immersion in boiling water renders them thick, firm, and somewhat crisp. When dried they become thin, clear, and transparent, and, if preserved from humidity or the attacks of animals, may remain long unchanged. The experiments of Hatchett, Fourcroy, and Vauquelin, show that they contain gelatine and a little albumen; but no precise information on their chemical composition has yet been given.

The principal character of the serous membranes is that of isolating the organs which they cover, and to the structure of which they are adventitious, and forming shut cavities, in which there is incessant exhalation and absorption. In some instances they evidently contribute to facilitate the mutual motions of contiguous and corresponding surfaces. From their free surfaces is secreted a fluid containing a small portion of albumen (Hewson, Experimental Inquiries, vol. ii. chap. vii.; Bostock, Nicholson’s Journal, vol. xiv. p. 147, and Medico Chirurgical Transactions, vol. iv.), which is greatly augmented during the state of disease.

The mode of developement of the pellucid membranes is not well ascertained. The investigations regarding organogenesy by Oken, Meckel, and Tiedemann, disclose facts which induce Meckel to hazard the opinion that some of them are not at all times shut sacs. I doubt, however, whether the fact which he adduces for this purpose implies the open condition of the pericardium and the peritoneum. In the case of the former the developement of the heart proceeds from the basis generally, without affecting the integrity of the investing membrane. In the case of the latter there is more reason to believe that, at the navel, at least, the peritoneum is either open, or is continuous with the vitellar membrane.

In the foetus the serous membranes are so thin, that [7:2:756]they are much more transparent than in the adult. In small animals also, they are more transparent than in large, and in cold-blooded animals than in the mammiferous. Of some also the disposition varies at different periods. Thus the descent of the testicle,—a process which has been well explained by Albinus, Haller, Wrisberg, and Langenbeck,—is attended with a remarkable change in the arrangement of that portion of peritoneum which the gland impels before it.

Synovial Membrane. (Membrana Synovialis ; Eursoe Mucosoe.)

Bichat enumerates several circumstances in which he conceives that serous and synovial membranes differ from each other. Gordon, who doubts how far the distinctions are well founded as the basis of anatomical arrangement, admits, however, the following peculiarities.

Synovial membrane resembles serous membrane in being a thin, transparent substance, having one smooth free surface turned towards certain cavities of the body, and another connected by delicate cellular tissue to the sides of these cavities, or to the parts contained in them. But it differs from serous membrane in the following circumstances. Is?, It possesses little vascularity in the healthy state; no blood-vessels are almost ever seen in it after death, nor can they be made to receive the finest injection. 2d , Its lymphatics are quite incapable of demonstration. 3d, Very delicate fibres, like those of cellular substance, or like the finest filaments of tendon, are distinctly seen in it after slight maceration. 4tΛ, It is considerably less strong than serous membrane. On these grounds, therefore, synovial membrane is to be anatomically distinguished from serous membrane.

The synovial membrane, as described above, is found not only in each of the movable articulations, but in those sheaths in which tendons are lodged, and in which they undergo considerable extent of motion, and in certain situations in the subcutaneous filamentous tissue.

The distribution of the synovial membranes is much the same in all these situations. They are known to line the ligamentous apparatus of each joint, capsular and funicular; and they are also continued over the cartilaginous extremities of the bones of which the articulation consists. This continuation, which was originally maintained by Nesbitt, Bonn, and William Hunter, and was demonstrated by various facts by Bichat, has been lately questioned by Gordon and Magendie, the former of whom especially thinks it unsusceptible of anatomical proof. The cartilaginous synovial membrane is certainly not so easily demonstrable as the capsular, for the same reason which I have already assigned regarding the difficulty of isolating the capsular pericardium, the ovarian peritoneum, and the serous covering of the tunica albuginea, — the want of filamentous tissue.

The presence of synovial membrane in the articular cartilages is nevertheless established by sundry facts. 1$?, If a portion of articular cartilage be divided obliquely, and examined by a good glass, it is not difficult to recognise at one extremity of the section a thin pellicle, differing widely in aspect, colour, anchstructure, from the bluish-white appearance of the cartilage. 2d , If the free surface of the cartilage be scraped gently, it is possible to detach thin shavings, which are also distinct from cartilage in their appearance. 3d , The free surface of the cartilage is totally different from the attached surface, or from a section of its substance, and derives its peculiar smooth polished appearance from a very thin transparent pellicle uniformly spread over it. 4th , If articular cartilage be immersed in boiling water, this thin pellicle becomes opaque, while the cartilage is little changed. 5th, Immersion in nitric or muriatic acid, which detaches the cartilage from the bone, gives this surface a cracked appearance, which is not seen in the attached surface, and which is probably to be ascribed to irregular contraction of two different animal substances. 6th , The existence of this cartilaginous synovial membrane is demonstrated by the morbid process with which the tissue is liable to be affected. On the whole, therefore, little doubt can be entertained that the representation of their course, as given originally by Nesbitt, Bonn, and Hunter, is well founded.

The same views may be applied to the synovial linings of the tendinous sheaths, which are equally to be regarded as shut sacs.

Attached to the free surface of each synovial membrane is a peculiar fringe-like substance, which was long supposed to be an apparatus of glands (glands of Havers) for secreting synovial fluid. It is now known that these fringes are merely puckered folds of synovial membrane, and that, although synovia is abundantly secreted by them, this depends merely on the great extent of surface which is the necessary consequence of their puckered arrangement This arrangement is easily demonstrated by immersing an articulation containing the fringed processes in clear water, when they are unfolded and made to float, and show their connections, figure, and terminations. They are analogous to the free processes of serous membranes, and like them are double, and contain adipose matter.

The synovial sheaths (bursae mucosoe) are very numerous, and are generally found in every tendon which is exposed to frequent or extensive motion.

Though the fluid prepared by these membranes has been examined by Margueron, Fourcroy, John Davy, Orfila, and other chemists, it cannot be said that its chemical composition is accurately determined. It is said to contain water, albumen, incoagulable matter regarded as mucilaginous gelatine, a ropy matter, and salts of soda, lime, and some uric acid. On the presence of the incoagulable gelatine depends its utility in diminishing friction in the finer kinds of metallic machinery employed in watches and chronometers.

BOOK II .

DESCRIPTIVE, PARTICULAR, OR SPECIAL ANATOMY. Special Anatomy may be defined to be that science, the province of which is to determine the shape, situation, and component parts of the several textures and organs of which the human body consists. In the course of this, however, it is requisite to premise some observations on the external shape of the. body, and the different regions into which it has, for the sake of greater precision, been divided.

The external shape of the human body is so well known, that it is superfluous to describe it. Besides its division into right and left halves, anterior and posterior surfaces, it.is divided into head, trunk, and extremities. The trunk is subdivided into neck (collum), chest (thorax, pectus), and belly (abdomen). The extremities are subdivided .into thoracic or upper, and pelvic, abdominal, or lower.
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The shape of the head is ellipsoidal, or oblong spheroidal; the greater diameter being antero-posterior, and the transverse smallest. The neck is cylindrical, spreading out above and below. The shape of the trunk is that of an irregular cylinder, flattened before and behind, broad above, and tapering below the chest, but expanding again at the pelvis. The extremities affect the cylindrical form, inclining to the conical.

These several parts may be still further subdivided. The head is distinguished into two great divisions, the head proper, and the face. The former corresponds to the scalp, and may be divided into coronal, temporal, parietal, and occipital regions. The coronal or syncipital may be reckoned from the anterior margin of the scalp to the site of the anterior fontanelle, or the line named the coronal suture. Behind this to the crown (vertex), and downwards on each side, are the parietal or lateral regions; from the parietal and frontal is the temporal; from the crown to the flexure of the neck is the hind-head or occipital (occiput); from the last point to the level of the shoulders is the cervix ; on each side are the lateral regions of the neck; and before is the laryngeal, jugular, or anterior (jugulum). The face consists of the brow, front or forehead (frons), with the glabella or mesophryon at its base, in the middle, and the eyebrows (supercilia) on each side; the nose (ηαsus), the upper lip (supralabium), the lower lip (infralabium), the chin (mentum), the cheeks (genoe), the chops (buccae), and the upper jaw (malae), and lower jaw (maxilla).

The chest, besides its distinction into right and left halves, anterior and posterior surfaces, and upper and lower boundaries, may be distinguished into a sternal region in the middle (sternum), a mammary region on each side, an axillary region, a costal region, a hypochondriac region, a scapular region, and a vertebral region.

The abdomen may be distinguished into regions in the following manner. The triangular space between the false ribs and navel, commonly named the pit of the stomach, is the epigastric region (scrobiculus cordis, epigastrium). Below this, in the centre, is the umbilical (umbilicus), with the iliac region or flanks (ilia) on each side, and the hypogastric (hypogastrium) below. Behind, on each side of the vertebral column, are the loins (lumbi).

Next to the abdomen is the pelvis, the posterior lateral parts of which are the buttocks (nates), the anterior the pubes, and the inferior the hips or ischiatic regions (ischia), with the perinaeum in the middle between them.

In each pectoral extremity are recognised the following divisions; the shoulder (humerus), the armpit (axilla), the arm (brachium), the elbow (cubitus), the fore-arm (antebrachium), the wrist (carpus), and the hand (manus). The latter is subdivided into the fore-wrist (metacarpus), the fingers (digiti), the palm (vola), and the back-hand (thenar).

Each abdominal extremity presents the following separate regions; the haunch (coxa), the thigh (femur), the knee (genu), the ham (poples), the leg (tibia), of which there is the muscular part or calf (sura), the ankle external and internal (malleolus externus et internus), the foot (pes), subdivided into the ankle-joint (tarsus), the foot-joint (metatarsus), the toes (digiti pedis), with dorsal or upper surface, and palmar surface or sole (solea).

These divisions, though not so numerous as they have been made by some, are sufficiently so for the purpose of general anatomical description. Where more minute distinction is requisite, it shall be introduced as we proceed.

The stature of the body varies in the two sexes, in individuals, in families, in tribes, and in nations. The Romans, when they first visited Gaul, remarked the gigantic stature of the ancient inhabitants of that country compared with themselves; and, generally speaking, the modern Italians, though by no means a pure or unmixed breed from the ancient stock, are a diminutive race. The Germans, and most of the English and Irish, are rather tall. The inhabitants of Finland are distinguished for their great stature, amidst the dwarfish tribes by which they are surrounded. In general, the Europeans are taller than the Asiatics.

The average height of the adult male varies from 5 feet 8 inches to 5 feet 10 or 11 inches, or even to 6 feet. The dimensions of different parts vary according to those of the whole body; but the following measurements of a male of 5 feet 8 inches, and one of 5 feet 11 inches, may communicate some idea of the length of different regions of the body.
[table]

The average height of the female varies from 5 feet 3 inches to 5 feet 5 inches and 5 feet 7 or 8 inches. A woman of 5 feet 10 inches is unusually tall. The length of the different regions is proportionally less than in the male.

The length of the body previous to adult age varies with the period of life. The length of an embryo of three weeks, represented by Soemmering, is about ⅛ of an inch; one of eight weeks is about 1 inch; and one at the end of the fifth month is about 10 inches. According to Burns, however, the length of the foetus in the fifth month does not exceed 6 or 7 inches; in the sixth it is about 8 or 9, in the seventh about 12, and in the eighth about 15 inches. At the period of birth, the average length, according to Roederer, is about 201/2 inches.

The only part of the foetus of which it is important to determine the average dimensions at the period of birth is the head. Its largest diameter, which is that from the crown to the chin, is in general about 5 inches. The transverse diameter between the parietal protuberances is at the same time about 3 inches. Of 60 male and 60 female infants born at the full time, whose heads were measured by Dr Clarke, the circumference passing through the occipital process and the middle of the brow was at an average 13∙8 inches, while the arch from ear to ear over the crown was 7∙32 inches. One measured 15 inches in circumference, and one 8 1 / 2 inches from ear to car; but.
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none were under 12 inches in the one direction, or 6į inches in the other.

It is well established that there is a difference in the average dimensions of the male and female, even in the foetal state. Roederer found the mean length of 16 male children born at the full time to be 20Ļ§- inches, and of 8 females only 20 1 ÷-; and of the 60 male and 60 female infants measured by Dr Clarke, the average circumference was 14 inches in the former, and only 13⅛ in the latter; and the parietal arch was 71- inches in the former, and 7j- in the latter. Of 120 infants, in 6 only, which were males, did the circumference of the head exceed 14⅛ inches.

The weight of the adult male varies from 9 stone to 11 or 12. Ten stones, or 140 lbs., may be stated as the average. The female weighs about 8 stone, and rarely more than 10. After the age of 35 or 40, when fat begins to be deposited, the weight rises considerably; and the average weight at this age is from 13 to 14 stones. In some extraordinary examples of corpulence, combined with large stature, the weight of the body amounts to 20 and 25 stones.

The average weight of the foetus in the early months is uncertain. According to Mr Burns, it weighs about 2 oz. in the 12th week; about 1 lb. in the 6th month; and about 4 or 5 lbs. troy in the 8th month. At the period of birth the mean weight is about 7 lbs. avoirdupois. Dr William Hunter states, that of .several thousand new-born perfect infants weighed at the British Hospital in London by Dr Macaulay, the smallest was about 4 lbs., the largest about 11 lbs. 2 qz., and the greater number varied from 5 to 8 lbs. avoirdupois. He knew no instance of a newborn infant weighing 12 lbs. Of 60 male and 60 female infants weighed by Clarke, the lightest was 4 lbs., the heaviest 10 lbs., and the average 7 lbs. 13 dr. avoirdupois. The average weight of 26 children at the natural period, weighed by Roederer, was about 6∣ lbs.; the lightest about 5⅜ lbs., and the heaviest about 8 lbs.

The difference between the weight of the male and female infant at birth is estimated by Dr Clarke at about 9 oz. avoirdupois, which agrees with the results obtained by Roe derer.

In the case of twins, the average weight of each twin is in general less than that of children born at single births; but the combined weight of both is greater. Dr Clarke found the average weight of 12 twins to be 11 lbs. avoirdupois each pair; the heaviest being 13 lbs., and the lightest 8ļ lbs. Mr Burns, however, states that he has known instances in which each twin was rather above than below the usual weight of a single-birth child.

Special Anatomy has been divided, according to the classes of textures of which the human body is composed, into different parts, with appropriate denominations. Thus the anatomy of the bones has been named osteology, osteography, and skeletology ; while that of the soft parts in general has been denominated sarcology. Where more minuteness is attempted, the anatomy of the soft parts has been still further subdivided into that of the ligaments, syndesmology ; the muscles, myology ; the vessels, angiology; the nerves, neurography and neurology ; the membranes, hyrnenology ; the glands, adenography and adenol^ogy ; and the internal organs, splanchnology.

Though these are convenient terms to designate the several divisions of Special Anatomy, they afford little assistance in the general arrangement of the subject. It is justly observed by Bichat, that this arrangement, if such it can be named, is objectionable, by separating different organs which ought to be united. It is indeed remarkable only for connecting organs by arbitrary, and often unnatural principles; and though it may answer in a subordinate manner, it is unfit to furnish the principles of a general and natural mode of arrangement.

The most eligible method is that which arranges the organs according to their physiological purposes,—a method adopted by Haller and Soemmering, but which required the hand of Bichat to give it its full and perfect developement, and which has since been adopted from this author by Cloquet.

According to this method, the organs of the human body may be arranged in three great classes: first, those pertaining to the animal functions, or which establish the connection between the individual and the objects of the external world—the organs of relation ; secondly, those pertaining to the organic functions, or which tend to the continuance of the individual—the organs of nutrition; and, thirdly, the organs relating to the continuance of the species—the organs of reproduction. The first class contains the organs of locomotion, speech, and sensation; the second those of digestion, circulation and absorption, respiration, and secretion; and to the third are referred the organs of generation.

This method may not be altogether free from objections; several of which are anticipated by Bichat. It is sufficient, however, to observe that it is less objectionable than any other; and one of its advantages is, that it furnishes a clearer and more precise idea of the connection of the different classes of organs of the animal body than any other yet proposed.

This method of arrangement may be conveniently exhibited in the following table.
[table]
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PART I.

ANATOMY OF THE ORGANS OF THE ANIMAL, VOLUNTARY, OR RELATIVE FUNCTIONS.

The organs belonging to the functions of animal life are those of locomotion, sensation, voice, and innervation. These organs are distinguished by two general characters, symmetry of form and harmony of action. By the first is meant that each organ possesses similar parts on each side of the mesial plane. By the second is meant that the action of that part which is on the right side of the mesial plane corresponds with that on the left.

CHAP. I. THE ORGANS OF LOCOMOTION.

The organs of locomotion maybe arranged in two orders, active and passive. The first are the agents of motion, or the organic substances which produce motion: the second are the bodies moved, or the instruments of motion. The muscles, strictly speaking, are the former, though to these are added certain appendages. The bones and their appendages constitute the second.

With the latter order of parts it is usual to begin the business of special anatomy, for obvious reasons. The bones are at once the most durable and regular in shape of all the organic solids; and as an intimate relation subsists between their mechanical figure and the soft parts connected with them, the knowledge of the former constitutes the best introduction to that of the latter species of organs.

SECT. I. OSTEOLOGY, SKELETOLOGY.

The assemblage of bones composing the human body constitutes the skeleton, which, like the body, is divided into head, trunk, and extremities. The length of the skeleton is about an inch less than that of the body; that is, the skeleton of an individual 5 feet 8 inches in height is about 5 feet 7 inches long, and of one 6 feet, about 5 feet 11 inches long. The weight of the skeleton varies at different periods of life. That of a middle-sized adult ranges between 160 and 200 ounces. A male skeleton, measuring 5 feet 6 inches long, I found to weigh 168 ounces, or 101 lbs., avoirdupois.

The number of separate pieces amounts to 254, of which 56 belong to the trunk, 60 to the head, 72 to the pectoral extremities, and 66 to the pelvic. Of these several parts, the trunk is the most important, because, Isŕ, it is developed before the head or extremities; and, 2dly, because if we look to its place in the animal kingdom generally, it is the most essential and constant, and presents the general modulus or type according to which the osseous pieces composing the head are constructed.

The Trunk.

The trunk of the skeleton consists of three parts, the spine or vertebral column, the chest or thorax, and the pelvis.

§. 1. The Spinal or Vertebral Column. (Spina Dorsi ; Vertebrae.)

The vertebral column, situate in the posterior part of the trunk, the length of which it determines, unites the head to the pelvis, supports the former, and is supported by the latter. When completely developed, it consists of 29, and rarely of 30 pieces, named vertebrae (spondyli, βπονόυλοι), from the circumstance that each admits of a slight*degree of rotatory motion. Twenty-four of these bones, which are in the healthy adult separate, are denominated true vertebrae (vertebrae veree). The 25th, named the sacrum, though in adult life forming a single bone, consists in early life of four separate pieces, which become consolidated, and are therefore named false vertebrae, (vertebrae spuriae). The four last constitute what is named the coccyx. The column thus formed, though straight at birth, assumes afterwards several curvatures in the antero-posterior direction, giving it the aspect of the Italian f. It may be divided into four regions, the cervical, dorsal, lumbar, and sacral. In the first it is almost straight, but begins to bend backward in the second, so as to form a considerable curvature with the convex surface posteriorly. A little below the middle of the dorsal portion it bends forward, and continues to do so to the lower part of the lumbar region, where it once more bends backward, and forms the sacrum into a concave hollow. At the lower end of the sacrum it again inclines forward, and the coccyx is in general considerably incurvated anteriorly. (Plate XXVI. fig. 1.)

Besides the antero-posterior curvatures, there is in general a lateral one near the lower part of the dorsal region, on the left side, to which its concavity is directed. This has been observed by anatomists, from Cheselden, who first represented it, to Soemmering, Bichat, and Meckel.

In length the vertebral column does not vary much; and differences in stature depend more on the dimensions of the members than of it. In thickness it augments progressively from the cervical to the sacral portions, after which it once more tapers to a point. It may be compared to two cones united by their base, the superior of which is truncated.

The vertebrae, true and false, possess certain common characters. Of these the most general is the annular shape, or a ring of bone, the opening of which, in continuity with those of the whole column, constitutes a longitudinal cylindrical cavity for lodging the spinal chord and its envelopes. It is therefore denominated the hole of the spinal marrow (foramen medullae spinalis, Soem.), or simply the vertebral hole (Bichat). Anterior to this is a mass of bone, generally the largest of the vertebra, and therefore named its body (corpus vertebrae). The anterior surface is flat, sometimes slightly convex; the posterior is always concave; the upper and lower surfaces are slightly concave, and correspond with the intervertebral fibro-cartilages.

Behind the hole the vertebra is moulded into an arch or annular segment, the outer surface of which forms seven processes. The first at the back of the vertebra on the median line is the spinous process, which may be said to be formed by the union of the spinal plates in the middle. On each sidesare two, which, from their situation with respect to the column, are named transverse processes. Other four, two on the upper and two on the lower surface of each vertebra, near the base of each transverse process, are named oblique, from their direction, and articular (processus articulares), because the inferior ones of the superior vertebra are articulated with the superior ones of the lower vertebra. These processes are easily distinguished by being covered with cartilage and synovial membrane. They constitute true capsular joints.

Each vertebra presents four notches or depressions, two at the upper and two at the lower surface, between the body and the oblique processes. Each of these, with corresponding notches on the vertebra above and below, forms a hole (foramen conjunctionis, vel intervertebrale), for the exit of the spinal nerves and the entrance of blood-vessels.
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All the vertebrae, excepting the atlas and vertebra dentata, are united in the same manner, and at the same points. The bodies are united by the intervertebral fibro-cartilages, which consist of white concentric annular layers of fibrous matter, placed in juxtaposition, and containing internally semifluid jelly. In adults this substance becomes firm and consolidated; but in the young subject it is so soft and compressible, that young persons are found to be one or two inches taller in the morning, or after they have been some time in the recumbent position, than in the evening, or after the spinal column has sustained for some hours the weight of the person. In advanced life these fibro-cartilages become still more solid and shrivelled; and in some instances they are converted into bone, so as to unite two or more vertebrae in a single mass. This change is one reason of the greater stiffness and incurvation of the spine in the old and decrepid, than in those in early life.

Besides the connection by the intervertebral cartilages, the vertebrae are united at their articular processes by means of capsular ligaments, so as to allow slight flexion and extension on each other; and at the basis of the spinous processes, by means of short, firm, and inelastic yellow chords (ligamenta flava), named yellow ligaments. These, with a thick fibrous fascia extending along the anterior surface of the bodies (ligamentum anterius, fascia longitudinalis anterior), a similar fibrous fascia behind, lining the vertebral canal, a ligament connecting mutually the apices of the spinous processes, and the incumbent muscles, retain the vertebrae firmly in their places, and prevent them from being dislodged, unless by a force adequate to break the bones and rend the ligaments.

The vertebrae vary in structure. The bodies consist chiefly of loose cancellated tissue, without solid bone. The spinal rings and the processes are much more firm and dense.

In the foetus and infant each vertebra consists of three portions, a thick, loose mass, corresponding to the body, and two lateral arches corresponding to the spinal rings, without spinous process, and scarcely meeting. In the foetus, indeed, the posterior wall of the vertebral canal may be said to be incomplete. Soon after birth, however, the spinal plates enlarging, mutually coalesce on the median line; and from this point of union, by successive accretion, the spinous processes arc gradually formed. These facts may serve in some degree to explain the facility with which tumblers and rope-dancers may be habituated in infancy to the most extraordinary inflexions of the trunk.

The vertebrae, agreeing in the characters now enumerated, differ from each other according to the regions which they occupy, and the parts with which they are connected. On this principle the twenty-four true vertebrae are arranged in three classes; the cervical (v. cervicis), the dorsal (v. dorsi), and the lumbar (v. lumborum).

The cervical vertebrae are in number generally seven, rarely six or eight; the dorsal are twelve; and the lumbar are five. (Plate XXIV. and XXV. fig. 1.)

The cervical vertebrae arc distinguished by their bodies being small, with flat anterior surfaces; by the articular processes being short and flat, as well as less oblique than those of the others; by their transverse processes being short, of a triangular shape, hollowed above, and perforated at the base by a hole for the transit of the vertebral artery; by the spinous processes being short, nearly horizontal, and generally biful; and by the vertebral hole being large and of an oval shape.

The first and second of these vertebrae are still further distinguished by peculiarities of configuration. The first, which is named atlas, consists of a large bony ring, inclosing an irregular hole, approaching to the shape of the ancient lyre. Instead of the body, which is wanting, is a mere arch of dense bone, with an obtuse tubercle before for the longus colli muscle, and behind an articular facette which applies to a corresponding one of the tooth-like process of the second vertebra. From the extremities of this arch the vertebral hoop acquires considerable thickness, for the formation of the oblique and transverse processes. The superior oblique process is seen above on each side in the form of an elliptical cartilaginous surface, slightly concave, consisting of two parts, the anterior large, the posterior small, and terminating in a point which overhangs the sinuosity of the vertebral artery. The cavity of this superior oblique process receives the condyloid process of the occipital bone, with which it is connected by a capsular ligament, lined by synovial membrane. Below is seen the articular facette of the inferior oblique process, rounder, shorter, less concave, but covered also by cartilage and synovial membrane, and articulated with the superior processes of the second vertebra. Between these two, on the lateral regions of the vertebral ring, is the transverse process, in the shape of a triangle, the base of which is formed by the bone of the oblique processes, and the sides by the production of the anterior and posterior arch. The latter, being the segment of a smaller circle, is more distinctly circular than the former, and may be described as a strong, dense, semiannular piece of bone, with a tubercle on its posterior margin at the median line, to which the rectus capitis posticus minor is attached. On the inside of the atlas, at the lower margin of the superior oblique process, is a rough surface with a depressed cavity, which marks the insertion of the transverse ligament. The space anterior to this is occupied by the tooth-like process of the second vertebra; that pos« terior to it, which is the proper vertebral hole, by the beginning of the spinal chord.

The atlas is connected above to the occipital bone by the capsular ligament, which surrounds the margins of the superior oblique processes; below, to the vertebra dentata in the same manner; and behind its anterior arch to the tooth-like process. To its anterior tubercle are attached the longus colli and rectus capitis internus minor ; to the transverse process the rectus lateralis, the superior and inferior oblique muscles, the levator anguli scapula, the transversi, the scalenus anticus, and the transversus cold. To its posterior arch the rectus posticus is attached.

By the condyloid processes of the occipital bone moving on the superior oblique processes, the head is bent and extended, or moved backwards and forwards on the atlas.

The atlas ossifies by two points.

The second vertebra, named axis and epistropheus, from its motions, is distinguished by a large prominent body like a tooth (processus odontoides) issuing vertically from its body, a circumstance from which it is also named vertebra dentata. This process, which is a four-sided prism, with the top obliquely acuminated,' presents on its anterior surface an articular facette, corresponding to that of the atlas. The posterior surface is rough, and corresponds to the transverse ligament. From the odontoid process the body descends somewhat below the level of the vertebral hoop, and presents at its lower margin, on the median line, a tubercle, with excavations on each side. Above, on each side of the odontoid process, are the superior oblique processes, in the shape of oval facettes, covered by cartilage and synovial membrane, and articulated with the inferior oblique processes of the atlas. Below, and a little behind, is the inferior articular process, more oblique in direction, and articulating with that of the third vertebra. Between the two is the transverse pro[7:2:761]cess, with the vertebral hole in its base; and from the same point the spinal plates converge backwards so as to form the spinous process, which is distinct and biful in this vertebra. Between the superior oblique process is the upper notch, which is rather a rounding of the spinal plates thana distinct depression; and between the inferior oblique process and the transverse process is the lower notch, which, with the upper one of the third vertebra, forms a complete hole for the exit of the fifth pair of spinal nerves.

The vertebral hole in this vertebra is heart-shaped, the basis before and the apex behind.

By the odontoid process it is articulated with the occipital bone and the atlas; by the upper oblique process with the atlas; and by the lower oblique process with the third cervical vertebra.

To the transverse process are attached the splenius capitis, levator anguli scapuloe, scalenus, transversus cervicis, longus colli, intertransversalis secundus anterior et posterior. To the spinous process are attached the rectus capitis posticus major, obliquus inferior, spinalis cervicis, interspinalis cervicis, and multifidus spinoe.

The axis ossifies from four points, one for each side, one for die body, and one for the odontoid process.

The third, fourth, fifth, and sixth cervical vertebrae are very similar. The bodies gradually increase in size to the seventh, which is generally the largest. The articular processes are also more oblique in the lower ones than in those above. The spinous processes also increase in size in the lower cervical vertebrae, and in the sixth and seventh are particularly large and prominent; and in the last are not biful, but merely tubercular. The vertebral holes in the second and third are heart-shaped, and the lower ones triangular, with the apex towards the spinous processes. The body of the seventh also presents at its lower margin a depression, which, with a corresponding one in the first dorsal, receives the head of the first rib. The seventh, in short, may be regarded as indicating the transition from the cervical to the dorsal vertebrae.

Besides the muscles already mentioned as attached to the axis, to the cervical vertebrae are attached the lumbocostalis, the serratus posticus superior, the rlwmboideus minor, the cucullaris, the splenius capitis, the upper part of the large complexus, and part of the rhomboideus major.

The dorsal or thoracic vertebrae (v. dorsi vel thoracis), which are twelve in number, are distinguished by articular notches on their superior and inferior margins, which, with die intervertebral cartilage and the contiguous vertebrae, form depressions for lodging the heads of the ribs, and cartilaginous facettes on their transverse processes for articulating with similar facettes on the tubercles of the ribs. The tenth dorsal vertebra has often only one facette above, and the eleventh and twelfth have only a single facette for each of the two last ribs.

The bodies of the dorsal vertebrae are more convex and somewhat rounder before than those of the cervical and lumbar. The hole, which is smaller, is also rounder, approaching to the oval shape.

The spinal plates are broad and strong, and meet behind in long prismatic spinous processes, which are directed obliquely downwards, so that they are imbricated over each other, especially in the middle of the back. The three last are less pblique. The oblique direction and imbricated arrangement of the spinous processes are connected with the peculiar flexuous bend which the column undergoes from the lower part of the cervical to the upper end of the lumbar region.

The twelfth dorsal vertebra approaches the first lumbar in the large size of its body, in the shortness of its transverse processes, in the straight direction and smaller extent of the spinous process, and in the articular processes becoming almost vertical.

To the dorsal vertebrae the following muscles are attached: the splenius capitis et colli, trachelo-mastoideus, the part of the complexus called biventer cervicis, the complexus, longus colli, transversus colli, spinalis colli, semispinalis dorsi, multifidus spinae, the inner part of the lumbocostalis, the levatores costarum, the inner layer of the tendon of the internal oblique and transverse muscles of the belly, the latissimus dorsi, rlwmboideus major, cucullaris, and serratus posticus superior et inferior.

The five lumbar vertebrae are distinguished by the size of their bodies and their processes, and by the direction of the spinous and articular processes. Each body is both broader and thicker, but less convex, than those of the dorsal vertebrae. The vertebral hole also is larger, and it resumes the triangular shape as in the neck. The transverse processes are broad, flat, and large, without articular facette like the dorsal, or arterial hole like the cervical, and are rough by the attachment of the sacro-lumbalis. Of the articular processes, which are large and have a vertical direction, the upper is concave, oval, and turned towards the median plane; the lower is convex, oval, and directed towards the lateral regions. The spinous processes are large, flattened, almost square, with thick obtuse margins, and directed straight backwards. The vertebral notches are large, and form holes much larger than at any other part of the spine.

The attached muscles are the spinalis dorsi, multifidus spinoe, quadratus lumborum, the inner layer of the internal oblique and transverse, and the outer layer of the latter, the external and internal parts of the lumbo-costalis, the latissimus dorsi, serratus posticus inferior, the diaphragm, and the psooe.

The sacrum, composed in early life of five pieces, which are afterwards consolidated into one, may be regarded as a series of imperfect vertebrae conjoined into a single mass. It is a symmetrical bone, of a triangular shape, with the base attached to the last lumbar vertebra, the apex, which is obtuse, adhering to the os coccygis, and the sides wedged between the bones of the pelvis.

The anterior or pelvic surface is concave, with the base, sometimes named theyww«o«ton/, prominent andoverhang-ing, the apex and the lateral margins incurvated forwards, and corresponds to the rectum. It presents in general four, sometimes five pairs of oval holes, which communicate with the spinal cavity, and between each of which may be seen a transverse ridge marking the lines of junction of the several bones; and in some instances the inner is so imperfect that a deep line is left. These holes, therefore, through which the nerves pass from the spinal chord, are quite analogous to those formed by the union of the vertebral notches. The posterior surface of the sacrum is much more irregular. At the top are two articular processes, concave and cartilaginous, for receiving the convex surface of the inferior articular processes of the last lumbar vertebra. Outside of these is a deep notch, which, with that of the same vertebra, forms the posterior vertebral hole; and outside of this is a tubercle, which corresponds to the transverse processes of the true vertebrae. Below the notch on each side is a series of four holes, which, like those of the anterior surface, communicate with the cavity of the bone, and allow the posterior nerves to issue from the chord. On the median line, between, there is an irregular bony ridge, or rather a series of three spinous processes, short, obtuse, and separated, by shallow depressions. The third of these diminishes gradually in the longitudinal direction till it is entirely lost [7:2:762]opposite the fourth pair of sacral holes, leaving between two ridges a triangular opening, which often communicates with the interior of the spinal cavity, and, when it does not, marks the lower termination of that cavity. In the former case it is closed by the posterior sacro-coccygeal ligament.

The sides of the sacrum, which are rough, and of an irregular cuneiform shape, present two surfaces,—one anterior, something cartilaginous, for articulating with the ilia'c bones,—the other posterior, marked by two deep sinuosities, in which are lodged the sacro-iliac ligaments. The inferior termination of the sides tapers towards the apex or coccygeal end. The surface is rough for the insertion of the sacro-ischiadic ligament, and it is terminated by a notch for the exit of the fifth pair of posterior sacral nerves.

The structure of the sacrum, like that of the vertebrae, is cancellated, and most loose in the site of the spinal plates and processes. Its mode of ossification is analogous to that of the vertebrae generally. On the middle plane appear five points, which correspond to the bodies of the false vertebrae, or the individual bodies of the sacrum; and on each side of these are formed two others, which become eventually the ridges of bone between the anterior and posterior sacral holes and the spinal plates. As these enlarge, they coalesce; and consolidating, leave only on the pelvic and dorsal surfaces the rows of holes through which issue the sacral nerves. It hence results that the sacrum is ossified from fifteen separate portions of bone.

Besides the muscles connected with the lumbar vertebra?, the sacrum gives attachment to part of the glutaeus maximus and the pyriforrnis.

The sacrum is attached above to the last lumbar vertebra by the intervertebral fibro-cartilage, the capsule of the two articular processes, and the yellow ligament of the spinous processes; to the iliac bones by the sacroiliac synchondrosis, and to the coccyx by a similar fibro-cartilage. (Plate XXIV. fig. 1, S.)

The coccyx is a symmetrical bone, triangular, occupying the posterior and inferior parts of the pelvis, attached by its base to the sacrum, and with the apex free and slightly incurvated forwards, so as to terminate in a hooked point, which has been supposed to resemble the bill of the cuckoo, (κoκκuξ, cuculus.)

The anterior or pelvic surface is concave, marked with transverse grooves covered by periosteum, and supporting the lower extremity of the rectum. The posterior or outer surface is convex, gibbous, and unequal, for the insertion of the sacro-coccygeal ligament and some fibres of the large glutaeus, and, like the anterior, is also marked by transverse grooves.

The base or upper end of the coccyx is concave before for articulation with the sacrum, and presents behind two tubercles continuous with those of the spinal region, and on the sides two notches, which, with those of the sacrum, form holes for the fifth pair of sacral nerves. The margins of the bone are rough, for the attachment of the small sciatic ligament, and meet below at an angle, which is sometimes biful, sometimes obtuse, and to which the levator ani is attached.

The coccyx is generally cellular, with little density. The transverse grooves by which it is marked indicate its original separation into five portions, two of which becoming united, leave four and occasionally three portions, an upper, a middle, and a lower. These portions, indeed, are so long in consolidating, that they are often separate in the adult. The first is the largest, and resembles a diminutive vertebra without hole, and with truncated or undeveloped processes. A lateral portion on each side projects like a wing, the rudiments of the transverse processes; and the two tubercles above noticed, rising like horns, are imperfect articular processes, meeting those of the os sacrum. The bony ridge which descends from these are imperfect spinal plates; and as these do not meet, they leave between them a groove corresponding to the anterior half of the vertebral hole; and the spinous processes are wanting. In the second coccygeal bone, which is rounder than the first, the aliform portions corresponding to the transverse processes are also smaller than in the first; and in the third and fourth they are diminished so much that they are scarcely cognizable.

The series of bones now described form by their union what is called the backbone, chine, spine (spina dorsi), or vertebral column. Viewed in connection, it may be distinguished into an anterior and a posterior region, two lateral surfaces, a base, and an apex.

The anterior region is large in the neck, narrow in the back, and broad in the loins and pelvis. A series of transverse grooves of variable depth marks the bodies of the vertebrae; and a series of transverse elevated ridges distinguishes in like manner their upper and lower margins. These grooves, which in the cervical vertebrae are confined to the front, extend in the dorsal and lumbar to the sides. This anterior region is covered by the anterior vertebral ligament. On the sides it answers in the neck to the anterior or great recti, and the longi colli muscles; in the chest to the latter, to the vena azygos on the right, and the thoracic aorta on the left; in the abdomen to the abdominal aorta and the inferior cava; and in the pelvis to the rectum.

In the posterior region are seen, on the mesial plane, the row of spinous processes, horizontal above and below, and imbricated in the middle. The intervals, which are considerable in the neck and loins, are much contracted in the back, in which extension brings the processes in contact. The apices of all are in general in the same straight line; but this may be disturbed, either from the wrong direction of a process, or an unnatural position of a vertebra.

On each side are seen the intervertebral grooves (fissura interspinales), which commence at the occipital bone, and are continued with those of the sacrum. Broad and horizontal above, smaller and more oblique in the middle, very narrow below, these grooves are formed by the series of spinal plates, between which are left spaces varying in size according to the obliquity of the plates. These spaces are occupied within by the yellow ligaments, which being inserted at their inner surface, are something broader than the spaces, and without by the transversus spinoe muscle.

On each side also is recognised a longitudinal hollow, extending from the atlas to the lower end of the sacrum. This hollow, which is formed by the spinous processes and the transverse processes with the spinal plates below, is superficial at the neck, narrow and deep in the back, and narrow and superficial at the loins and sacrum. In this longitudinal groove is lodged the muscle named multifidus spinae. (Plate XXV. fig. 1.)

The lateral regions present first the row of transverse processes, which vary in direction in different regions, chiefly in consequence of the spinal curvatures. Thus, if a vertical plane pass down along the sides of the column, the transverse processes of the neck and loins will be anterior to it, while those of the back will be behind it. In the first region these processes are distinguished for forming, by the series of holes in the base of each, a bony canal traversed by the vertebral artery, and which is com[7:2:763]pleted in the intertransverse spaces by the intertransversales colU. To these transverse processes numerous muscles are attached. Between them in the neck, and anterior to them in the back and loins, is a series of holes formed by the union of the vertebral notches. Through these, which are the intervertebral holes (foramina intervertebralia), and which increase in size from the neck to the loins, where they are considerable, the anterior branches of the spinal nerves pass. Their shape is elliptical and their transit short. Anterior to these processes in the dorsal vertebrae are the depressed facettes, in which, with those of the fibro-cartilages, the heads of the ribs are lodged.

The base of this column, which is supposed to be the last lumbar vertebra, is articulated with the sacrum in such a manner as to form an anterior convexity and a cavity behind. The base, however, may with greater justice be placed in the upper half of the sacrum, which, being firmly wedged between the thick posterior margins of the iliac boncs, transmits to them, and thereby to the bones of the pelvic extremities, the weight of the trunk. The mechanism of this is similar to that of the keystone of an arch, which the sacrum truly represents. The perpendicular pressure on this bone is counteracted and balanced by the lateral pressure of the iliac bones; and this lateral pressure is sustained, partly by their mutual pressure on each other before at the pubis, but chiefly by the oblique pressure of the neck of the thigh-bone, and the perpendicular pressure of the cylinder of the latter and those of the leg-bones.

The upper extremity of the column, which is formed by flic atlas and axis, receives the weight of the scull and its contents, which are exactly balanced on the articular cavities of the former bone. On this also the head is bent or extended by its proper muscles. Rotation is performed by the motion of the atlas with the head on the articular cavities of the second vertebra, and round its odontoid process.

The holes of each vertebra form, by union, the vertebral canal, in which are lodged the spinal chord, the origins of its nerves, and its membranous coverings. This canal, which is continuous with the cavity of the scull by means of the occipital hole above, and is completed by the sacral canal below, is not in the centre of the spine, nor is everywhere of the same dimensions. Situate behind the vertebral bodies, and before the spinal plates, it is nearer the posterior than the anterior region of the column. Large at the neck and upper part of the back, it diminishes below, and again enlarges in the loins. Its area is triangular in the cervical region, oval in the dorsal, and triangular again in the lumbar and sacral regions. It follows the different curvatures of the spinal column. In the recent state, it is formed not by the bones only, but before by the intervertebral cartilages, and behind by the yellow ligaments and the interspinales and intertransversales muscles. Lined by periosteum, by the posterior vertebral ligament, and by a quantity of loose cellular tissue, it is further covered by a cylindrical fibrous membrane, similar to the dura mater, the outer investment of the spinal chord; and within this are contained the ligamentum denticulatum, the spinal arachnoid, and the spinal chord itself, with its anterior and posterior nervous roots on each side, and its appropriate blood-vessels. In early life the soft parts predominate; and the canal and its component bones are then susceptible of much freer and more extensive motion than afterwards, when ossification is complete, and the fibro-cartilages acquire firmness.

In the human subject it may be viewed as a firm but flexible bony cylinder, which performs several functions at once. Resting on the sacrum, which is wedged immovably between the iliac bones, it supports the trunk in the erect position, and transfers to the sacrum, on which it rests, the weight of the head, the chest, and great part of the abdomen. In the vertebrated animals in general it incloses the spinal chord, one of the most essential and constant parts of the nervous system. In the several regions it forms a sort of posterior protecting wall to several important vital organs.- Thus, in the neck it forms a posterior barrier to the oesophagus, the windpipe, and the great sympathetic. In the back it constitutes the posterior wall of the chest; and in the loins and pelvis it is the posterior wall of the abdominal viscera and the large vessels.

In answering these ends, it is important to remark, that the firmness and mechanical arrangement of the spinous processes are of essential service. Their imbricated arrangement renders it impossible for any foreign body to enter the vertebral cavity and injure the spinal chord, unless between the occipital bone and atlas, or between the atlas and axis; and even at these points much precision is requisite to enter the cavity. Between the axis and the third vertebra it is more difficult, and below this next to impossible, without breaking the spinous processes.

With this character of security and support, the vertebral column unites a high degree of flexibility. Though the degree of motion between each vertebra is trifling, yet between several it is considerable, and between the whole twenty-four it is multiplied to a great amount. The motions of which the vertebral articulations admit are those of flexion and extension, rotation, and lateral flexion. Of these, flexion is that which is most extensive; for in the anterior direction there is less impediment to the motion of the vertebrae than behind, where the spinous processes allow no great extent of motion, unless where the habit has been acquired in early life, before ossification is completed. The rotatory motion of one vertebra on another is small; but by combining the motion of several or of the whole column, it becomes so extensive that some individuals can turn the head and neck more than half round. That these motions arc the passive result chiefly of the intervertebral cartilages and the articulations of the oblique processes, may be inferred from the fact, that when the former are ossified, or the latter ankylosed, the motions are much impaired generally, and wholly destroyed in the vertebrae affected.

The motions of the head on the atlas have been already shortly noticed. Those of the atlas and occipital bone on the axis arc, though simple in effect, complex in mechanism. The motion, indeed, is limited to that of rotation; but this rotation is extensive. This is favoured by the horizontal position, and the large extent of the inferior articular processes of the atlas, and the superior ones of the axis, the looseness of the articular capsule, and the absence of spinous process in the atlas. The axis and its odontoid process becoming the fixed point, the atlas, and with it the occipital bone and scull, turn on the elliptical flat articular surfaces, and on the odontoid process. On the first they glide extensively, and in opposite directions, while the capsular ligaments are stretched. On the odontoid process the motion is more limited, and from, right to left, and conversely; and in the latter variety of motion, the arch of the atlas before, and the transverse ligament behind, move on the anterior and posterior facettes of the odontoid process.

The anatomical construction of this articulation, however, which is so favourable to extensive motion, is attended with the disadvantage of facilitating the luxation of the atlas on the axis. Luxation, indeed, may be regarded[7:2:764] as produced by too extensive motion of these bones, in which the articular processes of the former vertebra abandon those of the latter, and instead of resting on them, are placed on the same plane, while the spinous processes are separated at least half an inch. It may be further observed, that the want of fibro-cartilages between these bones before, and of yellow ligaments behind, is favourable to displacement. The effect of this change of position on the spinal chord is-obvious. While the one side of the atlas is thrust off the axis, the other is forced so near its body and articular process, that it compresses the spinal chord, and may occasion palsy or immediate death, by injuring the chord above the origins of the phrenic and intercostal nerves. The vertebral arteries at the same time undergo so much stretching, that the blood cannot move through them with the natural facility.

It is nevertheless probable that displacement rarely occurs without such injury to the ligaments as to allow more extensive luxation than that now noticed. The odontoid ligaments, or the transverse, may be ruptured; and in either case the odontoid process is allowed to slip backwards, and plunges into the chord, and destroys its texture almost instantly. These ligaments may be ruptured either immediately by sudden violence, or in consequence of previous disease. In such circumstances, the injury done to the spinal chord is followed by almost immediate death, in consequence of the influence of the phrenic and intercostal nerves being suddenly suspended. In the same manner, the insertion of a cutting instrument between the occipital bone and atlas, or between the latter and the axis, so as to divide partially or completely the spinal chord above the origin of these nerves, an operation known by the name of pithing, is followed by immediate death.

§ 2. The Chest. (Pectus, '∑.rr l 0ος, Thorax.)

The chest may be defined as an osteo-cartilaginous inclosure, of an irregular conoidal shape, flattened before, concave behind, and convex on the sides. Its upper extremity is truncated. Its basis is irregularly oblique. It consists of the sternum before, the twelve dorsal vertebra. behind, twelve ribs on each side, and twelve cartilages connecting the ribs and sternum.

The sternum (sternum, <rrεgνον, os pectoris) is a symmetrical, oblong, flattened bone, broad above, narrow in the middle, broad below, and terminating in a point placed perpendicularly on the anterior of the chest. It presents two surfaces, an anterior and posterior, two extremities, an upper and lower, and two margins. (Plate XXIV. fig. 1.)

The anterior or cutaneous surface, covered by skin, the aponeurosis of the sterno-mastoid and large pectoral muscles, and periosteum, is marked by four transverse ridges at intervals of an inch, indicating the lines at which the separate portions of the bone were united. The posterior, internal, or mediastinal surface, is a little concave, occasionally marked by a longitudinal depression in its middle; also presents transverse lines, but rather indistinct; is covered in the middle by the mediastinal cellular tissue, above by the sterno-hyoid and sterno-thyroid muscles, and on the sides by the triangulares sterni.

The superior or clavicular extremity of the sternum presents three crescentic sinuosities; one on the middle, bounded on each side by an elevated peak, hollowed before and behind, and one on each side, incrusted with cartilage and synovial membrane. The first of these corresponds with the trachea on the inside, and has the sterno-mastoid muscle inserted on each outside. With the two lateral cartilaginous surfaces the sternal extremities of the clavicles are articulated. Between the two is the inter clavicular ligament, and all round are the ligamentous fibres of the sterno-clavicular articulation. This upper extremity is about double the breadth of the bone at its middle. Below, the bone becomes narrow, and below the fourth ridge it seldom exceeds half an inch in breadth. Here it terminates in an appendage, which is generally named the pointed or ensiform cartilage (cartilago mucronata, c. ensiformis). The shape of this is by no means always the same. In some subjects it is a flat, thin, and pointed process, not always very firm, but more solid than cartilage; in others it is a flat thin bone, terminating in two thin hooked, points. In some it is obtuse and perforated. In some it is thrust forwards, in others it is bent inwards, or towards the one side. * To this process the aponeuroses of the recti abdominis are attached.

The margins of the sternum, which are generally about half an inch thick,presentseven articular depressions crusted by cartilage. The first of these, in which the sternal extremity of the first rib is lodged, is, immediately below the clavicular depression, superficial and rounded. The others, which are situate at the ends of the transverse ridges, and receive the cartilages of the next six ribs, are deeper, angular, and surrounded by elevated margins, to which, in the recent state, the circumference of a capsular ligament is attached. In general, the seventh depression is formed partly on the sternum, partly on the ensiform cartilage; and the intervals between the depressions are smaller below than above.

The sternum is chiefly cancellated, light, and loose, with little density, and a thin crust of compact bone. In the foetus and infant it consists of eight or nine square pieces, separated by transverse furrows, which, by the union of two, are easily reduced to seven, and afterwards to five. By the further union of two of these portions they are afterwards reduced to three; and in this state they remain so long in some subjects that Soemmering describes the sternum not as one bone, but as three. The first of these portions, which is uppermost, is irregularly heart-shaped, or rather octagonal, with the tracheal depression and the clavicular articulations above, the depression for the cartilage of the first rib on the side, and half of that for the second at its lower margin, where it unites with the second. The latteris merely the middle andlongest portion of the bone, and is occasionally in three portions, separated at the costal depressions. The third or lower portion is the ensiform cartilage, the ossification of which renders the bone complete.

The ribs may be defined to be long, flat, irregular bones, with an irregular semicircular curvature, placed on each side of the chest, at intervals of an inch or less, between the dorsal vertebrae and the sternum. In general their number is twelve on each side, rarely eleven or thirteen. Of these, seven are connected with the sternum before by individual cartilages, and five are connected indirectly to the cartilage of the seventh, without attachment to the sternum. The former are denominated true or sterno-vertebral ribs (costoe verae) ; the latter are styled false or vertebral (costae spuriae, vel nothoe).

Each rib varies in length, breadth, and the direction of its curvature. The upper ribs are' the shortest, and most incurvated in proportion to their length. The middle ribs, or the fourth, fifth, sixth, and seventh, are the longest, and form curves of the largest circle. The false ribs, which diminish in length from the eighth to the twelfth, are the least incurvated, or form curves of the largest circle. It is chiefly from the middle set that the common characters of these bones should be derived.

Proceeding on this principle, we find that each rib may be defined as a broad, flat, longitudinal bone, not only incurvated, [7:2:765]but twisted from the direction of its original curvature. Each rib has a vertebral extremity, a cartilaginous extremity, and a body. The vertebral extremity consists of a tuberculated angular head (caput), with two cartilaginous facettes united at an angular line for insertion in the intervertebral depressions with which they are articulated. In the first and twelfth, and sometimes in the eleventh, there is one facette only corresponding to the single vertebra with which these bones are connected. Immediately before the head the rib is contracted and rounded, so as to form a neck (collum), which varies from five to six or seven lines in length; and before the neck is a tubercle or process (tuberculum) divided into two portions, one internal, smooth, cartilaginous, and uneven, articulated with the transverse processes of the dorsal vertebrae; the other external, rough, giving attachment to the middle costo-transverse ligament. Anterior to the tubercle the rib is straight for about one inch, and rough by the insertion of the sacrolumbalis and longissimus dorsi muscles. Beyond this point, which is therefore named the angle (angulus), the rib begins to be incurvated circularly, and bent downwards, so that the surfaces, which were external and internal, become obliquely superior and inferior. To prevent confusion, however, they must still be .distinguished in the same manner.

The outer surface of the rib, therefore, is convex, and forms the outer bend of the circle. Behind, it is covered by the latissimus dorsi muscle. The internal, which forms the inner bend of the circle, is convex above, and forms a concave hollow below, bounded by two sharp margins; one proceeding straight from the head forwards, till it is lost about three inches from the cartilaginous extremity; the other, more acute, from the tubercle, and following the curvature of the rib to about two inches from the same point. In this groove are lodged the intercostal artery, vein, and nerve. The internal intercostale are attached to the inner lip of the margin; the external to the outer. The upper margin of the rib is obtuse behind, where the external intercostals are inserted; but becomes acute and rough before, where the internal intercostals are inserted. The anterior or sternal extremity of the rib is broad and large, and terminates in an oval hollow, in which the cartilage is inserted. In advanced life, when the union between the rib and cartilage is intimate, this hollow becomes less distinct.

Besides these common characters of the ribs, several present peculiarities deserving notice.

The first rib is short, almost semicircular, and its direction is such that its broad surfaces are superior and inferior, not external and internal, as in the others. The head of this rib possesses only one large articular facette, corresponding with the first dorsal vertebra, sometimes one large one, and a minute one corresponding with a small space of the last cervical vertebra. Its neck is short and round, and its tubercle is identified with the angle which is wanting. The superior surface of this rib is highly important. From the head and tubercle extends a rough surface, in which are inserted part of the scalenus posticus, part of the serratus magnus, and the scalenus medius. Next to this is a smooth, deep depression, over which the subclavian artery passes; then is an eminence, to which the scalenus anticus is attached; afterwards a superficial hollow, in which the subclavian vein is lodged; and, lastly, a rough surface at the sternal or anterior end, for the subclavian muscle. The lower surface of the first rib is uneven and slightly rough, but without groove at its outer margin.

The second rib resembles the first in direction, having rather an upper and lower, than an external and internal surface. The head is angular and acuminated, and the neck contracted; and the upper surface is rough by the serratus magnus ; but the lower surface, from the tubercle, begins to present an angle in the shape of an oblique surface, bounded below by a rough ridge, within which is the groove for the intercostal vessels and nerves. Anterior to this flat oblique surface the rib is twisted, and undergoes a change in direction. In the third the angle is not more distinct, and it is only in the fourth that this part is well marked. This character continues to the eleventh, when it becomes indistinct, and in which the tuberosity disappears, or at least is identified with the head, which has only one facette. The groove also is so short as scarcely to be observed. Lastly, the twelfth rib, which is often unconnected with the others by cartilage, is without tuberosity, groove, or angle, and has, like the first, only one facette at the head.

The true ribs are connected to the sternum by means of broad rounded pieces of cartilage, variable in length and direction in different ribs. That of the first rib is very short, rather broad, and its direction, though oblique from above downwards, is more horizontal than that of the inferior ones. The angle at which it unites with the sternum is acute above, and obtuse below. It is often ossified in the adult. The second is nearly horizontal, and follows the direction of the rib to which it is attached. The next five are more oblique from above downwards, as the lower end of the sternum inclines forwards, and the corresponding ribs bulge towards the base of the chest.

Each of these cartilages, invested by perichondrium, is attached by a rough surface to the anterior end of the rib; while the other extremity, which is rounded and covered by synovial membrane, is lodged in one of the articular depressions of the lateral margin of the sternum, and secured in this situation by a capsular ligament, strengthened by anterior and posterior fibrous bands.

The anterior or outer surface of the thoracic cartilages is slightly convex, the internal or posterior surface flat, inclining to concave, lined by pleura and covered by the triangularis sterni muscle. The upper margin is concave, the lower convex, giving attachment to the internal intercostal muscles, which in this region fill the intercartilagi-ņous spaces.

The cartilages of the five false ribs differ from those of the true, in not being articulated directly with the sternum. The cartilage of the eighth rib, after bending forwards and upwards, is attached to the seventh by a tapering point with a minute articular surface. The ninth cartilage is attached in a similar manner to the eighth, the tenth to the ninth, the eleventh to the tenth, and the twelfth is either attached in the same manner to the eleventh, or hangs free, though attached to muscles connected with the others. Hence the twelfth, and not unfrequently the eleventh, are denominated floating ribs. The whole of them are mutually connected by ligamentous fibres inserted into their perichondrial covering. The outer surface of these cartilages is covered by the recti and external oblique, the inner surface by the diaphragm and transversus.

Connected with the ribs in the same manner in which those of the true ribs are, these cartilages differ, however, in taking a direction, first of descent, then of ascent or of curvature. The spaces which they leave between them, instead of being rhomboidal, as those of the true ribs, are irregularly triangular.

In structure the costal cartilages belong to those of the cavities. Analogous to those of the larynx, they are dense, firm, elastic, whitish substances, without distinct traces of organization, and seem to consist chiefly of modified gelatine, to which they are with difficulty reduced by [7:2:766]long boiling. Their tendency to ossification is considerable. In few persons above 45 or 50 are they quite free from bony points; and in many they are at this period converted into firm bone. The cartilage of the first rib, especially, is often firmly ossified before 35. When they undergo this change, certain points in their substance are observed to assume an orange or tawny colour, and to exhibit a porous arrangement, with great hardness, turning the edge of the knife.

By long maceration the costal cartilages become soft and gelatinous, and are finally resolved into oval patches, separated by circular or spiral lines, with numerous perforations. It was perhaps on this account that Hérissant described them as consisting of spiral fibres.

The bones and cartilages now described, with the twelve dorsal vertebrae behind, constitute the bony skeleton of the chest, bearing a remote resemblance to a cone, with truncated apex and oblique base, or, more accurately, to the frustum of a cone. To form a just idea of this assemblage of parts, it is necessary to consider its surface external and internal, its circumference above and below, its transverse diameter, and its longitudinal extent.

The anterior region of the external surface, consisting of the sternum in the middle, and the cartilages on each side, is flattened, contracted above, wider and more prominent below. The intercostal spaces arc filled between the sternum and the ribs by the internal intercostale, behind this by the external and internal, and covered by the anterior part of the large pectoral muscle. Behind, the chest presents the vertebrae with their processes, the transverse processes articulated with the tubercles, the angles forming a line obliquely receding from the spine, the transverse grooves, the longitudinal groove on each side filled by the multifidus spinoe, and the space between the processes and the angles of the ribs occupied by the spinalis dorsi, the longissimus dorsi, and the sacrolumbalis. The intercostal spaces, from the spine to the angles, are filled by the external intercostals; and anterior to this are the two layers of muscles.

The lateral regions of the chest are convex, making a larger sweep below than above. They present on each side eleven intercostal spaces, the superior of which are shorter and broader than the inferior. These spaces, which follow the curved direction of the ribs, cannot be accurately defined in shape. Between the angles and the cartilages, where the curvature is greatest, they are occupied by the double layer of the external and internal intercostal muscles, which, lying inclined in opposite directions, mutually decussate in this tract. The lateral region of the chest is covered above by the serratus magnus behind, and the two pectorals before; below by the external oblique on the side, and the recti before. The inferior lateral region, which is formed by the cartilages of the ribs, is therefore named the hypochondres (hypochondria).

The inner surface of the chest is, before, correspondent to the outer surface, unless below, where the anterior inclination of the sternum makes the antero-posterior diameter greater. The posterior region is marked by the row of vertebral bodies, the prominence of which forms an imperfect partition, which separates the right and left halves of the thorax; and which, notwithstanding the posterior bend which the spine undergoes between the second and eighth vertebrae, diminishes the antero-posterior diameter of the chest. On each side is a large concave hollow, narrow above, wide below, and swelling most capaciously in the middle, the walls of which, formed by the ribs and intercostal muscles, are lined by the pleura, and the cavity of which contains the lungs.

The upper circumference of the chest, or its apex, is small, oval, transversely oblique from above downwards, and from behind forwards. Bounded before by the sternum, behind by the first dorsal vertebra, and on the side by the first rib, it is diminished by the clavicles; and while its antero-posterior diameter is occupied by the windpipe, oesophagus, and the large vessels connected with the heart, its lateral portions are so much contracted, that each thoracic half (demithorax) has here almost a conical termination. Its dimensions in the male skeleton of average size are about 16 inches. As the first rib has little or no motion, the upper circumference remains unchanged.

The lower circumference of the chest, which is much more extensive, is said to be nearly four times larger than the upper. This, However, is exaggerated; and I find its greatest dimensions in the male to be 32 inches, exactly double the small circumference. It is susceptible of enlargement from the revolving motion of the ribs. The first rib remains fixed, while the lower ones are capable of being rolled outwards on their heads, tubercles and cartilages, so that the transverse diameter of the chest is enlarged. The lower circumference of the chest presents anteriorly a large triangular notch (incisura trigona), with the apex at the ensiform cartilage, the sides at the margins of the cartilage, and the base represented by a transverse line uniting the tips of the twelfth rib on each side. This notch, which, in the recent state, is occupied by the heads of the recti muscles, with their fasciae in the middle, and the anterior margins of the external oblique at the sides, constitutes what is called the pit of the stomach (scrobiculus cordis), or the epigastric region (epigastrium).

The transverse diameter of the chest is small above, but gradually enlarges to the ninth or tenth rib. The average diameter measured between the inner margins of the first ribs on each side in the male skeleton is four and a half inches; the average diameter measured between the tips of the eleventh rib on each side is nine inches, which is also nearly the diameter between the inner margins of the fifth ribs; and the average diameter measured across the upper margin of the niňth rib, which is about the widest part, amounts to eleven inches. These diameters, it has been already said, are susceptible of slight enlargement, by reason of the lateral revolution of the ribs; and this motion is most extensive between the sixth and tenth ribs. Above the sixth and below the tenth it is trifling.

The longitudinal extent or altitude of the chest varies; but in the same male skeleton it amounts to twelve inches measured between the lower margin of the first rib and the upper margin of the eleventh, which may be regarded as the inferior limit of the osseous part of the chest. From the top of the sternum to the plane of the ensiform cartilage the distance is five inches and a half. If from the lower margin of a mesial plane representing the mediastinum, another plane be drawn on each side to the margins of the false ribs, the space inclosed on each side above this oblique plane will give some idea of the capacity of the thoracic cavities.

The dimensions above stated apply chiefly to the adult male, from about thirty to thirty-five years, and of average size. In the female the chest is generally smaller in every direction, rounder, and more taper towards its inferior region. Above, as far as to the fourth rib, it is said to be larger and more uneven before, so that it has less of the conoidal shape than the male chest. - It is also shorter.

The pectoral cavity is in general symmetrical, that is, [7:2:767]of similar shape and dimensions on each side of the mesial plane. Sometimes, however, without the interven- ' tion of disease, the greater convexity of two or three ribs on one side gives it a more ample appearance than on the other.

§ 3. The Pelvis.

This is the name given to the irregular-shaped bony cincture which terminates the lower extremity of the trunk, and which is connected to the spinal column by means of the sacrum. It consists in the adult of four bones, two lateral portions (ossa coxarum), and two on the mesial plane, the sacrum and os coccygis. The latter two have been already described. The lateral and anterior divisions now come under examination.

These consist of two bones, ι bne on each side, united with each other before by means of fibro-cartilage, and receiving between them behind, the sacrum, to which they are in like manner united by fibro-cartilage. These bones, which are denominated ossa innominata, coxal or haunch-bones (ossa coxarum), are of a very irregular shape, and may be divided into three regions, the superior or iliac, the anterior or pubal, and the inferior or ischial. These regions it is not easy to define accurately; but they will appear in the course of description, and they correspond to the original divisions of the bone in the foetal state.

The coxal bone presents two surfaces, an external or femoral, and an internal or pelvic; and a circumference, divided into superior margin, anterior margin, inferior margin, and posterior margin.

The external or femoral surface (dorsum), which is alternately concave and convex, presents behind a rough surface, to which the glutaeus maximus is attached; between this and a semicircular rough linea lunated hollow, in which the origin of the glutaeus medius is lodged; and between the upper semicircular line and the lower a convex and concave area, for the attachment of the ghttaeus minimus, and one or two inequalities, to which one of the tendons of the rectus femoris is attached. About an inch below is a large hemi-spherical cavity, with elevated circular margins, interrupted at the anterior and inferior comer, named the acetabulum, or cotyloid cavity, for receiving the head of the thigh-bone. Its inner surface is covered by cartilage, unless at the centre, where is a depression for the attachment of the triangular ligament of the thigh-bone. The lower part of the margin is marked by a deep notch, over which, in the recent state, is stretched a ligament, thus forming a hole for the transit of the vessels and nerves of the articular cavity. The surface behind the acetabulum is slightly convex, indicating its union with the upper edge of apart of the coxal bone, distinguished by the name of hipbone (os ischii), and may be denominated the post-acetabular or ilio-ischial eminence ; below, it is concave and sinuous, for the tendon of the obturator externus, and terminating in a sharp spine (spina ischii), to which the small sacro-sciatic ligament is attached. Anterior to the acetabulum is a large opening, named the thyroid or obturator hole, oval in the male, and triangular in the female, closed by a ligament attached to its circumference, unless at the upper part, where there is an oblique groove for the obturator vessels and nerve. The outer surface of the thyroid ligament supports the obturator externus muscle, the inner surface the obturator internus. The upper margin of the thyroid hole is overhung by a convex ridge of bone, which is named the pubal or the horizontal branch of the pubal bone (os pubis, pecten, os pectinis) from supporting the parts of generation, and which terminates at its inner or mesial margin in a spine or tubercle, to which the outer portion of the tendon of the external oblique muscle is attached. The inner or anterior margin of the thyroid hole is bounded by a broad flat bone, irregularly rough on the surface, broad above, where it is connected with the os pubis, narrow at the middle and lower part,' where it joins the ischial bone. To the upper part of this, which is named the descending branch (ramus) of the pubis are fixed the gracilis, the head of the adductores longus et brevis, part of the adductor magnus, and part of the obturator externus. The lower part, which is named the ascending branch (ramus) of the ischium, gives origin to the adductor magnus.

The inner or pelvic surface (venter) of the coxal bone may be divided into three parts. The first is posterior, rough, and irregular, for articulation by fibro-cartilage with the lateral margin of the sacrum. The second, which is abdominal, concave, and is named the iliac pit (fossa iliaca), contains the belly of the iliacus internus, bounded above by the circumference or crest of the bone; behind by a rough line which separates it from the sacral surface; before by a concave irregular bend formed above by the iliac, below by the pubal bone; and below by a sharp line (linea iliopectinea), which is insensibly lost on the spine of the pubis, and to the inner end of which is attached a reflected portion of Poupart’s ligament, named the ligament of Gimbernat. The third or pelvic surface, which is below, presents behind a flat, irregular-shaped, concave space, occupied by the levator ani and part of the obturator internus, the inner opening of the thyroid hole, the inner surface of the rami of the pubal and ischial bones, with inequalities for the origin of the obturator internus, and a sinuosity below the ischial spine for the motion of its tendon.

The circumference of the coxal bone is very irregular. The upper or iliac portion, which is semicircular, and is named thecrest (crista ilium ossis), is rough for muscular and tendinous attachments, varying in breadth from half an inch to a whole one, and is distinguished into an external aŋd internal lip, and an intermediate space. To the former are attached the external oblique, the latissimus dorsi, and the tensor vagince femoris ; to the latter are attached the transversus and the quadratus lumborum ; and in the middle space between the two is the internal oblique. The posterior end of the crest terminates in the posterior superior spinous process, to which part of the glutaeus maximus and the ilio-lumbar ligament are attached, and below the posterior inferior spinous process forming the upper extremity of the ischiatic notch. The crest terminates before in the anterior superior spinous process, to which are attached the fascia lata, the sartorius, and the upper end of the tendon of the external oblique, or ligament of Poupart, or what is named the crural arch. The anterior portion presents, first a small sinuosity, which separates the superior from the inferior spinous process, to which is attached the upper tendon of the rectus cruris. Between this and an eminence in the upper or horizontal portion of the os pubis, marking its junction with the iliac bone, and which may be denominated the ilio-pubal, is a large sinuosity, in which are lodged the tapering ends of the iliacus internus and psoas magnus. To the ilio-pubal eminence the psoas parvus is attached; and within thepubal eminence, and anterior to the linea ilio-pectinea, is a triangular space, to which the origin of the pectineus is fixed. This part of the circumference is terminated by the spine of the pubal bone, to which the first insertion of Poupart’s ligament, or the outer pillar of the inguinal ring, is fixed, On the mesial side of this is a rough tubercular surface, which by means of fibro*cartilage is united with a similar surface on the opposite side. To this, which is named the symphysis pubis, the second insertion of the ligament of Poupart, the pyramidales and the recti, are fixed.
[7:2:768]

The posterior-inferior margin is most irregular. Commencing with the posterior spinous processes, which are parted by a small notch, the margin is, immediately anterior to the lower process, formed into a large hollow, named the ischiadic notch (incisura ischii), bounded before by the spine of the ischium, to which is attached the anterior sacro-ischiadic ligament, with the superior head of the gemellus without, and the coccygeus within. A pretty large hollow, in which play the belly and tendon of the obturator externus, separates the spine from the tuberosity of the ischium, a large broad rough surface, the external surface of which gives support to the quadratus and adductor magnus, the inner surface to the lower head of the gemellus and the external or inferior sacro-ischiadic ligament, while in the middle are fixed the long head of the biceps flexor, the semitendinosus, and the semimembranosus. From the tuberosity the margin of the bone along the ascending branch of the ischium, and the descending branch of the pubis, becoiiιes narrow till it reaches the symphysis, when it again becomes broad and more irregular. To the former margin are attached the gracilis, the transversus perinoei, the erector, and the corpus cavernosum. The latter uniting with the Opposite bone by means of the interpubal fibro-cartilage, constitutes the symphysis pubis.

The iliac or coxal bones consist of cancellated matter, covered by a thin layer of compact bone. In early life, and in delicate subjects, this cellular matter is loose, abundant, and rather thick. At a more advanced period, when ossification is completed, and in strong muscular subjects, the proportion of this cancellated matter diminishes and sometimes disappears, so that the bone consists of two layers of dense, compact bone; and in some, even this, in the iliac fossa, is destroyed entirely, so that the bone appears perforated.

The coxal bone is formed originally of three pieces, one for the large upper portion (os ilium), a second for the anterior or pubal (os pubis), and a third for the inferior or ischial (os ischium). In the foetus, infant, and young subject, these three bones are seen quite distinctly separate, but adhering, by means of fibrous or fibro-cartilaginous tissue, along a line drawn by the ilio-pubal eminence through the acetabulum, and over its posterior convexity into the ischial notch. At the same time the crest and margins of the ilium are covered by a cartilaginous epi- physis ; the pubal bones are mutually attached by the same substance; the branches (rami) of the pubal and ischial bones are soft and membranous; the thyroid hole is merely a ligamentous notch; and the acetabulum is a broad, irregular, superficial depression, with fibro-cartilaginous margin. The connections of these three bones continue soft and cartilaginous for several years after birth, generally to the tenth, twelfth, or fourteenth, sometimes later; and this is the reason why the os innominatum has been described as consisting of three bones, the os ilium, os pubis, and ischium. After the last-mentioned period, however, these bones are firmly consolidated into one piece, in which, nevertheless, the original marks of separation may be recognised in the ilio-pubal and post-acetabular eminences above, and the meeting of the pubal and ischial rami below. The coxal bone, therefore, which thus becomes a single solid piece in the adult, ought to be always described as such; and the distinction into three component parts, which is confined to the foetal and early period of life, belongs to the history of its ossification.

The coxal bone is united to its fellow of the opposite side by the symphysis pubis, and behind to the sacrum by the sacro-iliac fibro-cartilage (synchondrosis). Both of these junctions are occasionally ossified in advanced life. By the cotyloid cavity it is articulated with the head of the thigh-bone.

The coxal bones on each side, with the sacrum wedged between them behind, and the os coccygis attached to its extremity, constitute an irregular-shaped osseous cincture, something conical, with the base above, and the truncated apex below. This shape, with the manner in which it supports the abdominal viscera and several of the urinary and genital organs, has given it the name of basin (le bassin, das becken, pelvis) or pelvis. In this it is requisite to consider the external and internal surface, the upper and lower circumference, the transverse diameters, the direction, the outlets and their dimensions.

The external surface comprehends four regions, the anterior or pubal, the posterior or sacral, and two lateral.

The anterior region presents the pubal articulation (symphysis) on the median line, and on each side the pubo-ischial rami, the thyroid hole and its margins, and the acetabulum or articular cavity. The posterior region presents on the median line the sacral spinous processes or spinous ridge, the triangular depression which terminates the spinal canal, the suture uniting the sacrum to the coccyx and the posterior convex surface of the latter; and on each side are the sacral grooves and posterior holes; the processes by which they are bounded without; a deep depression corresponding to the sacro-iliac synchondrosis, and which is filled by a thick bundle of ligamentous fibres; and lastly, the posterior tuberosity of the ilium, which projects much behind. The lateral regions are formed by the dorsa or external fossoe of the iliac bones, bounded below by the ischiadic notches.

The internal surface of the pelvis consists of two portions,—the one above, wide, capacious, and tapering downwards, forming the large pelvis; the other narrower, with walls nearly cylindrical, and forming a canal named the small pelvis.

The large pelvis presents, behind, the sacro-vertebral articulation and the sacral promontory, and on the sides the internal iliac fossae. Before, where osseous parietes are wanting, the space is occupied by the abdominal muscles. This constitutes the abdominal division of the pelvis, and supports in the erect position part of the ileum and colon. Its transverse diameter, measured between the crests of each iliac bone, amounts to nine inches in the male, and eleven in the female.

The large or abdominal division of the pelvis is bounded below by the ilio-pubal line on the sides and front, and behind by a line drawn between the posterior extremities of each side, but following the surface of the sacrum. The outline of this, which is elliptical, with the transverse diameter longest, and its plane inclined obliquely forwards, is named the superior outlet or aperture (ambitus superior) of the pelvis, and it constitutes at once the lower termination of the great and the upper boundary of the small pelvis. Its importance in the practice of midwifery renders it necessary to distinguish its calibre, which is larger in the female than in the male, into four diameters. The first, antero-posterior, from the pubal symphysis to the sacral promontory, is from four to five inches in the male, and four inches nine lines in the female. The second, transverse, measured between the iliac bones, is four inches six lines, sometimes five inches, in the male, and five inches six lines in the female. Two others, drawn obliquely from the sacro-iliac synchondrosis to the ileo-pubal eminence, are about four and a half inches in the male, and five inches in the female.

The small or proper pelvis, which is below this aperture, forms a sort of cylindrical osseous canal, more capacious, [7:2:769]however, at its middle than at the extremities, the lower outlet of which is diminished by the anterior incurvation of the sacrum and coccyx, while the sides are bounded by ’ the ischio-pubal branches. Before are the inner surfaces of the pubal symphysis and branches, corresponding to the urinary bladder; behind, the pelvic surface of the sacrum, corresponding to the rectum; laterally, the thyroid holes, the inner surface of the ischial-bone and ilio-ischial junction, and the isehiatic notch, completed by the anterior and posterior sacro-isehiatic ligaments.

The upper circumference is very irregular, with its plane slightly inclined forwards; larger in the female than in the male. It presents, behind, the sacro-vertebral articulation, bounded by a depression indicating the upper edge of the sacro-iliac synchondrosis; laterally, the two iliac crests terminating before in the anterior superior spinous processes; before, the hollow of the iliacus internus and psoas magnus, the ilio-pubal eminence, the horizontal branch of the pubal bone, its spine, and lastly its symphysis.

The lower circumference, which corresponds with the inferior aperture or ano-perineal outlet of the pelvis (ambitus inferior), is directed downwards and backwards. Bounded behind by the coccygeal bone, and on the sides by the ischial tuberosities, this outlet is thus distinguished for three eminences, separated by an equal number of notches. The situation of these eminences indicates the limits of the lower pelvic aperture. The size and disposition of the notches is inversely to that of the eminences; and their arrangement is such that an eminence is opposite to a notch, and conversely. Thus the anterior notch, which is formed by the pubal arch, is opposite to the sacro-eoceygeal eminence behind; and though the ischial tuberosities appear opposite to each other in one sense, strictly speaking their plane is each accurately opposed to the opposite sacro-ischial notch. The anterior notch is terminated above by an acute angle in the male, in consequence of the proximity of the pubo-ischial branches which form its sides, but by a rounded arch in the female, by reason of the separation of these branches on each side. In this notch are situate the generative organs of both sexes. The lateral notches, which are bounded behind by the sacrum and coccyx, before by the spine and tuberosity of the ischium, arc irregular in shape, and are each subdivided into three portions by the sacro-sciatic ligaments, which secure the articulation of the sacrum and coxal bones. The first of these ligaments, the posterior or external, arising from the posterior extremity of the iliae crest, from the sides and transverse processes of the sacrum and coccyx by a broad, firm web of fibres, becoming small and thick at the middle, again expands, and is inserted into the ischial tuberosity. This ligament corresponds behind to the glutaeus maximus, which is partly attached to it, before and mesially to the small or anterior ligament to which it is united. The small or anterior sacro-sciatic ligament rises, in common with the large one, from the transverse processes of the sacrum and coccyx, and adhering to it for half an inch, passes more horizontally outwards to the isehial spine, in which it is implanted by a broad, thick, fibrous web. Behind, it corresponds at its sacral end, and for an inch from this to the posterior ligament, and laterally to the pudic vessels and nerve; before, it serves with the posterior to complete the lower circumference of the pelvis.

By these two ligaments the ischiadic notch is in this manner converted into two apertures and a notch. The first of these is superior, and is bounded above by the ilio-ĩschial arch, and below by the small ligament and part of the posterior or large ligament. Through this hole pass the pyriformis, the sciatic nerve and artery, the gluteal artery, and the internal pudic artery. The second is an irregular triangular hole, smaller than the upper one, bounded above by the anterior ligament, below by the posterior one, and laterally by the sinuous hollow between the ischial spine and tuberosity. Through this aperture the tendon of the obturator internus passes out of the pelvis; and the external pudic artery and nerve, after bending round the upper ligament, re-enter the pelvis. The third space is a superficial notch, bounded on the outer or lateral side by the posterior ligament, and on the mesial side by the sacro-coecygeal bone. It is chiefly occupied by cellular tissue.

The dimensions of this inferior aperture are nearly the following. The antero-posterior diameter, from the coc-eygeal apex to the lower margin of the pubal symphysis, is 3 inches in the male, and 4 inches 6 lines in the female. The transverse diameter between the ischial tuberosities of each side is 3 inches 2 lines in the male, and 4 inches in the female. The oblique diameter, measured from the middle of one of the great sacro-sciatic ligaments to the opposite ischial tuberosity, is about 4 inches in the male, and from 4⅜ to 5 in the female. Of these diameters the antero-posterior is most liable to vary, by reason of the mobility of the os coccygis; but independent of this, it is always larger in the female than in the male, in consequence of the sacrum being less incurvated, and descending more in a straight line. It further appears, that in females who have born children the incurvation of the sacrum is much less than in those who have not.

The direction of the pelvis is not horizontal, nor does it correspond with that of the trunk. Articulated behind with the lumbar portion of the spinal column, the axis of which is inclined considerably forward from the vertical plane, the pelvis partakes of the same inclination. A horizontal line drawn from the pubis towards the sacrum passes in general an inch below the tip of the coccyx; and with this a line drawn from the pelvis to the upper margin of the sacrum, representing the plane of the pelvis, makes an angle of between 80° and 85°. The sacrum inclines from the vertical plane about 35°; but the inclination of the superior and inferior pelvic apertures varies. An imaginary line drawn from the tip of the coccyx to the centre of the small pelvis, to represent the axis, cuts the line of inclination at an angle of 75°. The most accurate axis of the pelvis is a line drawn at right angles to the plane of the pelvis as above found.

The dimensions given above are sufficient to show that the female pelvis is much more capacious and ample laterally than the male. In the female, indeed, it is important to remark that the upper region of the coxal bones is more prominent laterally, and hence renders the haunches prominent and rounded, and the outline of the abdominal aperture more extensive; the sacro-vertebral angle is less prominent, and the sacrum is broader and less incurvated; the arch of the pubis is wider and less angular; the ischial tuberosities are more apart, and the cotyloid cavities even are at more distance from each other,—a circumstance which determines the peculiar gatt of the female. The male pelvis, on the contrary, is deeper than the female.

In the infant the pelvis is small compared with the size of other bones, and of the parts which it is to contain. The dimensions of this part, in early life, are indeed so limited, that not even the urinary bladder can be said to be contained within it. As puberty approaches, the distinctive characters of the male and female pelvis begin to appear. While in both sexes the bones become larger and the cavity more capacious, in the female the additional[7:2:770] amplitude appears in the width of the haunches, and their remarkable projection beyond the flanks.

The Head.

The upper or atlantal extremity of the vertebral column supports the head, a complicated assemblage of bones, the general shape of which is spheroidal above and behind, and irregularly cubical before and below. It is naturally divided into two parts, which are distinguished by their mechanism, their use, and the mode of their developement. The first of these, the scull or cranium (κgawov, calvaria), forms a spheroidal bony case, occupying the superior and posterior region chiefly of the head. The second, which is the face, is formed above by an irregular pile of bones, articulated immovably to the anterior inferior part of the scull, and below by a single symmetrical bone, articulated movably to the middle of the lower part of the scull.

§ 4. The Scull. ( Cranium, Calvaria.)

The scull consists of eight bones, four of which are symmetrical and arranged on the mesial plane, and four arranged in pairs on each side. The four symmetrical bones are the frontal, the ethmoid, the sphenoid, and the occipital; the four lateral are the two parietal and two temporal bones.

The frontal bone (os frontis, os coroncs, synciput) is a symmetrical bone occupying the anterior part of the scull, and forming the anterior part of the scalp and the part of the face distinguished as the brow (frons). It may be divided into three surfaces, the external or frontal, the inferior or orbito-ethmoidal, and the internal or the cerebral, and a circumference. The external surface is frontal and temporal.

The frontal surface, which is convex and regularly arched, presents on the median line a ridge, indicating the original separation of the bone in two halves, the nasal protuberance, more convex in age than in youth, and corresponding to the smooth interval between the eyebrows (glabella), a serrated margin articulated in the middle with the nasal bones, on the sides with the ascending processes of the superior maxillary bones, and, lastly, the nasal spine, which supports the nasal bones. (Plate XXV. fig. 2. n.)

On each side of the median line are the large smooth surface of the upper part of the frontal bone, the frontal protuberances (tubera frontis), large in youth, small in advanced age; the superciliary arch (supercilium), an irregular convexity extending transversely about an inch on each side of the mesial line, most prominent within, where the corrugator supercilii is fixed; and, lastly, the orbitar arch, large and prominent at its temporal angle, smaller and more rounded at its nasal, and presenting either a hole, or a notch covered by a ligament (c. c.), and through which pass the frontal artery and nerve. The nasal end of the orbitar arch, sometimes named the internal angular process, is insensibly lost in the serrated surface, where it joins the superior maxillary bone. The temporal process, which is prominent, terminates in a serrated surface, which is articulated with the malar bone. Exterior to the frontal protuberance is a curvilinear ridge (d.), which gives attachment to the fascia of the temporal muscle, denotes the anterior boundary of the space in which that muscle is lodged, and separates the proper frontal from the temporal surface of the frontal bone. This ridge, descending in a circular direction, terminates in the temporal process at the opposite side to that of the orbital arch (a. á.) The triangular segment cut off by it is convex above and concave below.

The orbito-ethmoid surface is irregular. It presents first on the median line a quadrilateral notch with serrated margins, in which the ethmoid bone is articulated. These margins consist in adult subjects of two plates, between which are seen segments of the frontal and ethmoidal sinuses. In the outer of these tables are generally one or two holes, or notches, which, with the ethmoid bone, form holes (foramen orbitarium internum anterius et posterius). Through the former pass the ethmoidal twig of the nasal branch of the ophthalmic nerve; through the latter the posterior ethmoidal artery and vein. On each side of the ethmoidal groove is a triangular concave surface, which forms the vault of the orbit, near the outer margin of which, and within the external angular process, is a superficial pit for the lacrymal gland, and towards the nasal side a depression for the reflected tendon of the superior oblique muscle.

The internal or cerebral surface, which is concave, covered by the dura mater, presents on the median line a groove, the beginning of the sagittal, in which the superior longitudinal sinus is lodged, and the margins of which, converging below, form a crest corresponding to the upper margin of the falx. Below this is the foramen ccecurn, which in the bone communicates with the two canals belonging to the nasal bones, but in the recent state allows some veins to pass from the nose to the longitudinal sinus. It is sometimes common to the frontal and ethmoid bones. (Plate XXV. fig. 3. c.)

On each side the frontal bone presents the large cavities, in which are contained the anterior extremities of the hemispheres of the brain; and above these the bones rise in the manner of a vaulted arch. The whole inner surface is moulded into alternate pits and eminences, called digital and mammillary respectively, and which correspond to the eminences and depressions of the cerebral convolutions. These are most conspicuous at the lower part, where the surface is traversed by minute vascular grooves.

The circumference of the bone is serrated all round, for articulation with the contiguous bones. The posterior margin is nearly of an elliptical outline, straight, and interrupted below by the quadrilateral notch. Above, where the frontal is articulated with the parietal bones, the serrated processes proceeding from the outer table are largest and longest. Below, where the frontal is articulated with the lower angle of the parietal and wing of the sphenoid bone, the internal table is most prominent, so that the spheno-parietal suture is imbricated. Between the temporal and orbitar fossae this separation of the tables forms a triangular rough surface, which is articulated with a similar one, the triarcual surface of the sphenoid bone; and between this and the quadrilateral notch the margin is articulated in the same manner with the anterior margin of the sphenoid bone. Lastly, the serrated and cellular margins of the quadrilateral notch are connected with the ethmoid bone.

Besides these cranial bones, the frontal is articulated with the following bones of the face,—the nasal bones by the middle of the nasal suture, the superior maxillary bones by its sides, the lacrymal bones by the anterior end of the ethmoidal groove, and with the malar bones by the external angular processes.

The frontal bone, which is thick at the nasal protuberance and the external processes, and thin at the orbitar regions, is ossified by two points, which, appearing at the frontal protuberances, proceed by radiation as from a centre towards the circumference of the bone. In the foetus and early infancy the bone thus consists of two lateral portions placed between the pericranium and dura mater, [7:2:771] with a longitudinal interval on the mesial plane, e transverse one on the site of the coronal suture, and a triangular chasm at the angle between the two. This chasm, with a similar one between the frontal bones, forms a quadrilateral lozenge-shaped space, at which the motion of the brain is distinctly felt both at birth and for months after, and which is therefore named the fontanelle, or the anterior fontanelle (fans pulsatilis ; bregma), or the open of the head. As the ossifie process advances, the lateral margins of the bone extend, and the mesial margins extending mutually, at length coalesce, first at the nasal protuberance and along the forehead, afterwards above, until the fontanelle is progressively diminished and at length obliterated. This junction is effected by the formation of serrated processes, which are mutually dove-tailed into each other; and for some years after birth the frontal bone consists of two similar halves articulated by a middle suture. In some few instances, especially in the female, this continues for many years; and the individual is found after death to have the frontal bone in two halves, with a middle suture. More frequently, however, the suture is obliterated by the consolidation of its serrated margins, and the frontal bone consists of one piece. The points of ossification remain long distinct in the form of the frontal protuberances. But eventually, from the uniform elevation of the margins of the bone, they become less conspicuous; and in old age they disappear more or less completely, leaving a surface uniformly uneven.

The ethmoid or sieve-like bone (os cribriform^), which is symmetrical, and occupies the quadrilateral notch of the frontal bone, consists of several bony plates arranged at right angles, and parallel with each other, so as to give the whole a cubical shape. It consists of four parts, a horizontal plate, occupying both sides of the mesial plane; a vertical plate at right angles to it, and corresponding with the mesial plane; and a lateral plate on each side, also vertical and parallel to the middle plate. In the bone thus formed the following circumstances deserve attention. (Fig. 5.)

The superior surface, cerebral, covered by dura mater, is formed by the horizontal plate, perforated by numerous holes (lamina cribrosa), through which pass the fibrils of the olfacient or first pair of nerves depressed longitudinally on each side, but surmounted in the middle towards its anterior half by a strong process of a triangular shape, named the cock’s comb (crista galli), and to which is attached the anterior inferior extremity of the falx, or dichotomous membrane. The anterior margin of this process is generally marked by a groove which, with that of the frontal bone, forms a passage for the nasal vein into the longitudinal sinus. The posterior margin of the perforated plate is marked by an angular notch between two horns, for articulation with a salient angle of the sphenoid bone. The crista galli may be regarded as the upper division of the vertical plate, which occupies the mesial plane, and which is thick and sometimes biful before, but thin and rough behind, where it acts as a partition to the lateral halves of the ethmoidal cavities. The sides of this middle vertical plate are furrowed by minute canals (canaliculi), traced from the foramina above, in which the nervous fibres are lodged. This plate, and indeed the lower surface of the perforated plate, are covered by a fibro-mucous membrane, which has been named the pituitary or the Schneiderian. The vertical ethmoid plate is articulated at its lower margin with the vomer and the triangular cartilage of the nose, before with the nasal spine of the frontal bone, and behind with the median crest (processus azygos) of the sphenoid bone.

The lateral portions of the ethmoid bone consist externally of a smooth flat bone (os planum of the ancients), which forms the inner or nasal wall of the orbit, internally of two bones convoluted on themselves, and which are distinguished as the superior and middle turbinated bones (conchae, ossa turbinata superiora et media, ossa spongiosa). These bones are seen most distinctly behind; but to form a correct notion of their figure, it is requisite to detach the lateral portions and examine them separately, when the following peculiarities may be recognised. The ossa plana on each side terminate in concave oblong quadrilateral plates, diverging outwards from the vertical plane. A t the internal edge of these quadrilateral plates is seen above a convex bone, with numerous minute perforations, the orifices of short canals. This is the superior turbinated or spongy bone. Below, and a little to the external side, is a small groove, separated by a thin plate from a larger cavity, which is the superior meatus, leading into the posterior ethmoid cells. Below this, again, is the osseous plate, with perforated edges turned on itself from within outwards, so that its convex side is towards its fellow, and its concavity is below and laterally, and separated by another thin plate from the lower margin of the ossa plana. This is the middle turbinated bone, the longitudinal cavity of which communicates with the lower or nasal surface of the bone, and is bounded on its outer margin by the lower margins of the ossa plana, where they are articulated with the inner margin of the orbitar plate of the maxillary bone. The anterior deficiency of the ossa plana is occupied by the lacrymal bones.

The internal surface of these bones generally is covered by a thin fibro-mucous membrane, partaking of the characters of periosteum at its attached, and of mucous membrane at its free surface.

The ethmoid is articulated with the frontal bone, the sphenoid, the superior maxillary bones, the nasal, the lacrymal, the palate bones, the inferior turbinated bones, and the vomer, at the parts already indicated.

In structure the component plates are compact, unless at the crista galli, which contains some cancellated tissue, and the middle and superior turbinated bones, which seem less dense than the horizontal plate.

The ethmoid bone consists in the foetus of loose, soft, brown-coloured substance, contained in a thick vascular membrane, and disposed in the cubical shape, but without the complicated arrangement of convoluted plates by which it is afterwards distinguished. Into this the nervous fibrils penetrate, and are observed to be ramified. This continues at least four or five months after birth, when these fibrils become surrounded with compact bone deposited in their interstices, and in this manner the perforated plate is formed by deposition round the nerves. About the same time, on the mesial plane is observed a vertical plate, which gradually becomes condensed into solid bone, in the shape of the crista galli and middle partition. Soon after, as the bone increases in size, excavations are formed, and the soft uniform substance is removed, while plates of thin but solid bone interposed between thick vascular membranes are observed to be formed. The plates, which are slightly convoluted, become’thinner and more solid, and are at length moulded into the superior and middle turbinated bones. The ethmoid is generally complete about eighteen months after birth; and about the second year its different component parts may be recognised. The holes of the perforated plate are, however, larger and more numerous at this age than afterwards. The minutegrooves (canaliculi,) described by Scarpa, in the lateral portions, are also more distinct and larger than subsequently. It ossifies therefore in four points; [7:2:772]one for the horizontal plate, one for the vertical, and one for each lateral mass.

The sphenoid, wedge-like or cuneiform bone (os cuneiforme, os sphenoides, ∑φnvosibtζ) —a symmetrical bone, of a very irregular and complicated shape, wedged as it were between the bones of the scull, may be distinguished into cerebral or superior, and anterior-inferior or external surfaces. By the ancient anatomists it was compared to a bat with the wings expanded, and is by them distinguished into a body and wings, great and small. (Fig. 4.)

The cerebral surface, covered by the dura mater, is superior, and forms part of the internal base of the scull. It may be distinguished into four parts; the middle, the tipper anterior, and two lateral. The middle consists of a smooth surface, on which lie the olfacient or first pair; a transverse groove for the commissure of the optic nerves; a transverse eminence named the olivary (processus olivaris) ; a deep quadrilateral pit in which is contained the pituitary gland, named the Turkish saddle (sella Turcica, ephippium, fossa pituitaria), with a slight groove on each side for the transit of the sixth pair of nerves, and. bounded behind by an elevated eminence, with two processes, named the posterior clinoid or couch-like processes. The sides of the sella Turcica, especially before and behind, present generally a pit, in which is lodged part of the carotid artery. The anterior serrated margin of this surface is articulated with the ethmoid bone; the posterior with the cuneiform process of the occipital bone.

The upper anterior portions consist of two triangular spaces, united to the middle by their base. This surface, which corresponds to the anterior lobes, is bounded before by a serrated margin articulated with the frontal bone, behind by a smooth curved margin, which corresponds to the Sylvian fissure, and marks the separation of the anterior and posterior cerebral lobes. This arch, which may be named the sphenoidal, terminates before in a sharp process, named the ensiform, articulated with the frontal bone, and behind in a similar though smooth process named the anterior clinoid. Anterior to this, and between it and the olivary process, is the optic hole (foramen opticum), for the transmission of the optic nerves on each side. Behind this hole, and on each side of the olivary process, is the groove in which the internal carotid is lodged. The triangular surfaces now described are commonly named the small wings (alce minores sive superiores), or the wings of Ingrassias. (Fig. 4, a, a.)

The lateral surfaces are concave, marked with cerebral depressions and vascular grooves, four-sided, low behind, but rising to an angular peak before, and are commonly-named the large wings (alce majores, aloe mediae, Soemm.) (A, A.) From the small wing of Ingrassias it is separated by a longitudinal fissure, extending obliquely from the sides of the sella Turcica upwards and laterally. Through this opening, which is large below and narrow above, and is variously named the superior orbitar fissure, the sphenoidal fissure (foramen lacerum superius et anterius, 1,1), pass the third pair or oculo-muscular nerves, the fourth or pathetic, the first or ophthalmic branch of the fifth, and the sixth or abductor nerves, the optic vein, and a branch of the lacrymal artery. Behind, and a little to the outside of the sphenoidal fissure, is the round or superior maxillary hole (foramen rotundum, r, r), for the transmission of the second or superior maxillary branch of the fifth pair; and still more posterior and laterally the elliptical hole (foramen ovale), for the transmission of the third or inferior maxillary branch of the fifth pair. This part of the large wing terminates behind in ân angular process named the spinous, articulated with the petrous portion of the temporal bone, and in which is seen the spinous hole (foramen spinoswn), through which a branch of the external carotid, the middle meningeal artery (arteria durce matris media, maxima), enters the cranium to be distributed on the dura mater.

The lateral surfaces terminate before in an elevated recurved peak, surmounted by a triangular surface mostly serrated, but smooth behind, articulated with a similar surface of the frontal bone; laterally in a concave serrated margin articulated with the convex serrated margin of the temporal bone; and behind in a smooth margin, which, with a similar one of the pyramidal portion of the temporal bone, forms the anterior fissure of the base of the cranium (foramen lacerum anterius in basi cranH.)

The anterior inferior surface presents several distinct regions. On the mesial plane, at right angles to the serrated margin, is a vertical crest or spine, which terminates below in a process denominated therefore the azygos or rostrum, (a.) The upper crest is articulated with the vertical plate of the ethmoid bone, the lower with the fissure of the vomer. On each side the bone is convex, from the swelling of the sphenoidal sinuses, into which may be seen a small opening, which, however, is nearly closed by an osseous plate, variable in shape, named by Bertin the sphenoidal turbinated bone. The interior of the sinuses is parted into two halves by a middle plate, corresponding to the external crest. On each side of this middle portion is the outer surface of the small wings, forming part of the orbit penetrated by the optic hole, to the circumference of which are attached the levator palpebrae superioris and levator oculi above, the depressor oculi below, the adductor within, the abductor without, and the superior oblique (trochlearis) between the two last. Between the margins of the small and great wings is the outer orifice of the sphenoidal fissure; and on the other side of this is the orbitar surface, hollow, bounded above by the serrated margin of the triangular area, without by that of the malar process, and below by a smooth ridge, which, with the posterior one of the superior maxillary bone, forms the spheno-maxillary fissure. Immediately between this is the external orifice of the superior maxillary hole. External to the malar serrated edge is the zygomato-temporal surface, hollow, inclosed within three curvilinear serrated margins and two rounded ones, and parted into two portions, the temporal and zygomatic, by an elevated ridge, to which are attached aponeurotic slips of the temporal muscle. Below this transverse crest is a concave surface, lost in the external pterygoid process, and forming part of the zygomatic fossa, terminating, like the similar part of the large wing, in the spinous process, and presenting first the elliptical, and then the spinous hole.

The rest of the outer surface of the sphenoid bone terminates in two prominent bony plates, the one external, thin, and flat, the other internal, thicker, and more pointed, named the pterygoid Or wing-like. These processes rise almost at right angles to the plane of the posterior part of the lateral wings by a thick prismatic piece of bone, common at first to both. Soon, however, they become distinct, especially behind. The external plate, which is thin, broad, and sharp, rises from the lateral portion between the round and oval hole, and, with its plane turned obliquely outwards, terminates in an end round below and before, sharp behind, (b, b.) To the outside of this plate, which is irregularly rough, with part of the zygomatic fossa, is attached the external pterygoid muscle. The inside of the external plate is concave, and forms, with the internal, part of the pterygoid fossa, in which are lodged the internal pterygoid muscle and the external peristaphy-linus. The internal pterygoid process, rising on the inside, narrower and more curved, terminates in a bent point named the unciform or hook-like process (c, c), over which in a [7:2:773]peculiar groove moves the tendon of the external peristaphylinus. The base of the external process generally presents 'a longitudinal superficial depression named the navicular. Between the external and internal is left a triangular space, which is completed by the pyramidal portion of the palate bone. The base of the internal pterygoid process is penetrated by the Vidian canal (canalis Vidianus), larger before than behind, through which is reflected the posterior twig of the spheno-palatine ganglion, sometimes named the Vidian nerve (Plate X. fig. 2), to join the sixth at its connection with the great sympathetic, with some bloodvessels.

The posterior part of the body of the sphenoid bone presents a quadrilateral surface of some extent, rough, cartilaginous, and sometimes excavated into small cells, for articulations with the cuneiform or basilar process of the occipital bone. In the young subject this surface is soft and cartilaginous; but as age advances it becomes more solid, and is at length inseparably ossified with the occipital bone. From this circumstance Soemmering describes the sphenoid and occipital as one bone, under the name of spheno-occipital; a method in which he has been followed by Meckel. The bone, however, is so complicated in shape and the arrangement of its parts, that it is perhaps more intelligible to describe it separately.

The sphenoid bone is articulated with all the bones of the scull at the points already indicated, and with the following bones of the face—the malar, the palate bones, and the vomer, sometimes with the superior maxillary.

It consists, when fully formed, chiefly of compact bone; for the plates even of its cells, though thin, are compact and firm bone, and its general density is considerable.

In the foetus the sphenoid bone, after remaining cartilaginous till the third month, begins to ossify in the lateral portion, near the roots o f the pterygoid processes. Two other points of ossification appear on the large wings, and, coalescing with those already formed, constitute a single mass on each side for each lateral portion. About the same time the body in the sella Turcica begins to be formed; and shortly after the small wings are formed separately, and coalesce, first with each other, and then with the body. In the fifth month the bone has the same figure which it retains through life, but the extremities of the wings are soft and cartilaginous; the body of the bone is uniform, loose, bony matter; the holes are large and imperfect; the optic hole is triangular; the inferior maxillary hole and the spinous are incomplete behind—sometimes the latter is not formed; and the Vidian canal is a mere fissure between the base of the external and internal pterygoid processes. The bone at this time consists of five portions, one for each small wing, one for each large wing, and one for the body of the bone. At the period of birth, though these parts are still separable, in general the small wings become united with the body, and the bone thus consists of three pieces. Eventually, by the union of the two large wings with the sides of the body, the bone is consolidated into one portion, the optic foramen is rounded, the oval hole completed, and the Vidian fissure is at the same time converted into a canal. In this state the sphenoid continues for several years, growing in every direction, and diminishing the size of its several apertures; till, about the age of puberty, the body becomes excavated into two lateral cavities with compact walls, separated by middle partitions. These are the sphenoidal sinuses, the formation of which is generally simultaneous with the completion of the bone in all its parts.

The occipital bone (os occipitis, os proroe), symmetrical, of a rhomboidal or trapezoidal shape, placed on the median line, occupying the posterior inferior region of the scull, may be distinguished into three parts, the occipital bone proper, the condyloid processes, and its cuneiform or basilar process. It presents two surfaces, an external or occipital, and an internal or cerebral.

The external surface is convex and smooth above the middle, where it is covered by pericranium and the tendinous fascia of the occipito-frontal muscle. Nearly in the middle the bone is elevated into an irregularly triangular eminence named the occipital protuberance (tuber occipitis), the size and shape of which vary according to the energy of the muscles connected with the strong fibrous fascia named the cervical ligament. When most strongly marked, the apex of the protuberance to which the trapezius, by means of the ligament now mentioned, is fixed, is prominent downwards, and occasionally incurvated or unciform. From this prominence a line may be traced, obscurely at first, distinctly below, descending to the great aperture (foramen magnum), for the transmission of the spinal chord. To this ridge or crest (crista occipitis), which is not always exactly in the middle, a fibrous fascia of great strength is attached, from the protuberance to the aperture, giving support and attachment to the muscles on each side, and named the posterior cervical ligament (ligamentum cervicis, ligamentum nuchce). On each side of this ridge the surface is marked by various irregularities, the effect of muscular impressions.

A semicircular ridge, extending from the protuberance on each side to the margins, where it joins a similar ridge on the temporal bone, and named the superior semicircular, gives attachment above to the occipital part of the epicranius, the lateral parts of the trapezius below, and at its marginal end to that of the sterno-mastoid. When the crest begins to be distinct, a similar ridge proceeds in a semicircular direction to the margins of the bone, where it becomes more elevated, and occasionally changes its direction by a slight bend downwards and forwards. To the space between these two lines, which is rough and irregular, the complexus, and part of the rectus capitis posticus major, are attached within, and the splenius capitis without; while the rectus capitis posticus major and minor, and the obliquus capitis superior, are inserted by a strong fascia into the superior semicircular line. (Plate XXIV. fig. 6.)

The lower region of the bone presents the vertebral aperture, generally oval, with the large diameter antero-posterior, sometimes circular, occasionally rhomboidal or lozenge-shaped. At its anterior half are the condyloid processes, tipped with cartilage and synovial membrane, elliptical in shape, converging forwards, and parted by a sinuosity in the posterior part of the cuneiform process. By this opening the spinal chord with its membranes, and the spinal nerves, pass outwards, and the vertebral arteries enter the cranium. The posterior extremity of the condyloid processes is bounded by a depression, containing generally a small hole, sometimes two, for the transit of vessels not constant; externally is a rough surface, for the attachment of the rectus capitis lateralis ; and above is the anterior condyloid hole, for the transmission of the twelfth cerebral or hypoglossal nerve.

The portion of bone anterior to the great aperture is the cuneiform process, the outer surface of which is depressed behind for the insertion of the recti capitis interni majores and minares ; but smooth before, where it is covered by the mucous membrane of the pharynx.

The internal or cerebral surface, which is concave, is divided more or less regularly into four compartments, in the following manner. From the apex descends a groove nearly in the median line, though generally inclining a little to the right, to near the middle between the apex [7:2:774]and upper margin of the great aperture, where it makes a rectangular turn to the right, leaving in the middle an elevated eminence, on the other side of which a similar groove, though always smaller, proceeds to the opposite margin of the bone, while from the same point descends an elevated ridge, more or less acuminated, to within half an inch of the great aperture. This arrangement produces in the inner surface of the occipital bone a cruciform appearance, which is occasionally named the spina cruciata, while the compartments are distinguished as superior and inferior right and left occipital fossae. The rectangular groove, which is the continuation of the sagittal, formed in the inner surface of the parietal bones, contains first the lower part of the superior longitudinal sinus, then the lateral sinus, the plates of the dura mater being fixed to the lateral ridges on each side. The groove on the left side contains the left lateral sinus; and to the central tubercle and ridge the falx of the cerebellum is attached. In the two upper compartments, which are much marked by cerebral eminences and depressions, the posterior cerebral lobes are lodged, while the cerebellic lobes are contained in the inferior compartments. (Fig. 7.)

On each side of the large aperture is seen a short segment of a broad circular furrow, which terminates on the margin of the bone in a smooth sinuous depression. The first part is the termination of the lateral groove, containing the end of the lateral sinus; the second, the sigmoid notch, forms, with a similar one on the temporal bone, the jugular hole (foramen lacerum posterius in basi cranii, foramen jugulare, incisura jugularis), for the commencement of the jugular vein, the glosso-pharyngeal nerve, the nervus vagus, and the accessory nerve. Occasionally there is a proper notch for the nervus vagus in the anterior part, and occasionally one for the glosso-pharyngeal.

. Anterior to the large aperture is the inner surface of the cuneiform process, concave transversely for lodging the medulla oblongata before it quits the cavity of the cranium (fossa basilaris), marked by a groove at the sides for the inferior petrous sinuses, and terminating abruptly in a broad quadrilateral surface incrusted with cartilage, for articulation with the posterior part of the sphenoid bone.

The margins of the occipital bone posterior to the inferior lateral groove are serrated for articulation by suture with the parietal and temporal bones. The upper margins form a salient angle, nearly rectangular, for articulation with the re-entrant angle formed by the two parietal bones. The sides of this angle, however, vary in direction from the presence or absence of Wormian bones (ossa Wormiana, triquetra). Another salient angle, but always obtuse, is formed opposite the superior lateral grooves, for articulation with the re-entrant angle formed by the parietal and temporal bones of each side. A third angle is formed by the jugular eminence, an elevated process placed between the inferior lateral groove and the jugular notch, and which is tipped with cartilage for articulation with a corresponding surface of the pyramidal portion of the temporal bone. Anterior to the jugular notch the margin of the bone is smooth, but articulates by fibro-cartilage with the posterior surface of the temporal pyramid, leaving a small space unarticulated between the anterior extremities of both bones, which form a common aperture.

The occipital bone is thick along the crucial spine, the tubercles, and at the condyloid process; but thin in the centre of the four occipital fossae, at which the external and internal tables are united with little or no diploe, and are not unfrequently translucent. The cuneiform process is cancellated.

In the foetus it consists of four pieces, one for the occipital bone proper, one for each condyloid portion, and one for the basilar process. The ossification of the occipital portion commences near its middle, corresponding to a point above the occipital protuberance, and extends by radiating fibres all round to the margins of the bone. At this time the occipital portion has the shape of a cardium; and the apex not being formed, a space is left through which the brain is felt pulsating, named the posterior fontanelle. About the same time ossification appears in two quadrilateral portions on each side of the large aperture, and in an oblong parallelogram anterior to it. Though these enlarge and approach each other, at the period of birth the apex is still incomplete, and the posterior fontanelle is open; and even at the inferior angles of the occipital portion, where it joins the condyloid portions, a space of the same kind is left on each side. After birth, as ossification advances rapidly, the apex of the occipital portion is gradually enlarged, the Wormian bones on each side are formed, and the condyloid and basilar portions uniting with the occipital, the bone is consolidated about the third or fourth year. The traces of the lines of union may sometimes be recognised so late as the seventh year.

The occipital bone is articulated immovably by its margins with the sphenoid bone, the two parietal, and the two temporal bones; movably by its condyles with the atlas.

It is also connected with the second vertebra by means of a ligament, which passes from the odontoid process to the inner margins of the condyloid processes.

The parietal bones (ossa verticis, ossa bregmatis, ossa parietalia), two bones united with each other on the mesial line, are quadrilateral, quadrangular, convex externally, concave internally, occupying the upper, middle, and lateral parts of the cranium. (Plate XXVI. fig. 4 and 5.)

The external convex surface, which is covered by the epicranius above and temporal muscle below, presents above and behind a hole for an artery and vein, variable however in position and existence; in the middle the parietal eminence, prominent in youth, indistinct in advanced age; and somewhere between its middle and lower margin a curvilinear ridge, the continuation of that on the frontal bone, and terminating near the lower augle of the parietal for the attachment of the temporal fascia, below which the bone is covered by the temporal muscle.

The internal concave surface, lined by the dura mater, is marked by digital eminences and depressions corresponding to those of the cerebral convolutions. The superior edge is marked by a half-groove, which, with that of the opposite bone, constitutes the sagittal for lodging the superior longitudinal sinus; within this, depressions more or less deep, corresponding to the granules of Pacchioni; towards the centre the parietal pit, corresponding to the eminence of the external surface; and ascending from the inferior anterior angle arborescent grooves, in which the large meningeal artery is lodged, (m, m.) Parts of these grooves are occasionally converted into canals by the growth of bone over their margins.

The parietal bone is bounded by four margins. By the superior, which is serrated, it unites on the mesial plane with the opposite bone, forming the sagittal suture; by the anterior or coronal, also serrated, it is articulated firmly with the frontal bone, forming the coronal suture ; and the posterior, also serrated, forms with the posterior margin of the corresponding bone a re-entrant angle, in which the occipital, occasionally with Wormian bones, is articulated. The lower margin alone, which is a concave curvature, is obliquely acuminated before, acuminated and serrated in the middle for imbrication with the temporal [7:2:775]bone, and serrated behind for articulation with the upper margin of the mastoid process.

These margins form by union four angles, an anterior and posterior superior, and an anterior and posterior inferior, of which the most important is the anterior inferior, by reason of its presenting the origin of the meningeal groove on its internal surface. The parietal bone, consisting of an external and internal table, with interposed diploe, is thin, especially below its middle; and the diploe is small, and in some points obliterated. It is ossified from one point, commencing at the protuberance, and radiating all round to the margins. Previous, and some time subsequent to birth, its mesial margin and anterior and superior angle are not formed; and the brain is here covered by dura mater, pericranium, and integuments only, forming, as already mentioned, the bregma, or anterior fontanelle. By the completion of the bones, however, the margins and angles meet, and the fontanelle is closed. This is generally effected in the course of the second year.

The temporal bones (ossa temporum), rather irregular •in shape, are placed on each side at the lateral and inferior parts of the cranium.

Each bone presents an external or auricular surface, an internal or cerebral, and a circumference.

The external or auricular surface presents, above and before, a large convex surface, part of the temporal fossa lodging part of the temporal muscle; before, the zygomatic process, long, pointed, and terminating in a serrated extremity, where it is united with the malar bone to form the zygoma (fig. 2, z), to the upper surface of which the temporal fascia is attached, to the lower the masseter muscle; behind, a flat surface of an irregularly rounded shape, terminating before in the mastoid process (processus mammillaris, mastoideus, m), and behind in a serrated margin, which unites with the occipital bone. Between the mastoid process and the serrated margin behind is a rough surface for the splenius, small complexus, and sterno-mastoid; and below is a pit, in which the origin of the digastric muscle (biventer maxilloe) is lodged.

The zygomatic process is connected to the temporal bone by two roots, one of which, anterior, inferior, and transverse (processus transversus), forms the anterior brim of the glenoid or articular cavity, in which the condyle of the inferior jaw is lodged; the other, superior and posterior, forms first the external and then the posterior brim of the same cavity. Behind this posterior brim is an irregular fissure termed the glenoid (fissura Glasseri), which indicates the original line of separation between the superior or squamous and the inferior or pyramidal portion of the bone, and through which pass the tendon of the anterior muscle of the malleus, some vessels, and a nervous twig named chorda tympani.

In the angle between the mastoid and zygomatic process is an elliptical opening from five to six lines in diameter, leading into a cylindrical cavity, the direction of which is obliquely forwards. This orifice, which is the external earhole (meatus externus, o), leads into the tympanal cavity, from which it is separated, in the recent subject, by a thin membrane only (membrana tympani). The three lower thirds of this orifice are formed by a distinct bony ring, which is rough, and perforated by holes for the insertion of the cartilages of the external ear. On the outside of the lower part of this bony ring is a strong process, varying from half an inch to 12 lines in length, nearly round, but terminating in a sharp point, and therefore, from its resemblance to the style of the ancients, named the styloid process. (tf.) Behind its base, and between it and the mastoid process, is a small hole, the stylo-mastoid, for the exit of the facial nerve. (Plate XXVI. fig. 2.)

The inner or cerebral surface, marked by cerebral impressions and arterial furrows, is distinguished particularly by a pyramidal eminence of bone rising obliquely from it, and a deep sinuous groove, making part of the lateral, in which is lodged part of the lateral sinus.

The pyramidal portion (pyramis, fig. 3, p), named also the petrous (pars petrosa), from its hardness in several of the lower animals, may be distinguished as a truneated pyramid, bounded by four planes, one of which, the external, has been already described. Of the other three, one superior, marked by cerebral impressions, presents a semilunar depression for the Gasserian or trigeminal ganglion, the upper orifice of the carotie canal, a slight furrow, the extremity of the opening through which a branch of the Vidian nerve passes, and an eminence which indicates the situation of the superior semicircular canal. Another posterior, separated from the last by a sharp margin, traversed anteriorly by the groove of the superior petrous sinus, presents, first, an eminence indicating the posterior semicircular canal; and, secondly, an orifice, the internal auditory hole (meatus internus), parted by a septum into an upper orifice communicating with the Fallopian aqueduct for the facial nerve, and a lower pit containing minute holes communicating with the labyrinth, and transmitting the filaments of the eighth or auditory nerve.

The lower or third plane surface of the pyramidal process, which is external and connected with the occipital bone, presents, first, at the lower end of the external depression a cartilaginous, rough surface, where it adheres to that bone; then a large sinuous cavity, the jugular notch, forming, with that on the occipital bone, the hole for the exit of the jugular vein, often separated by a bony process into two, the first of which is for the nervus vagus, the second for the jugular vein; a sharp ridge (proeessus vaginalis) at the base of the styloid process, separating the jugular notch from the glenoid cavity; a circular hole, the external orifice of the carotic canal (canalis caroticus), for the entrance of the internal carotid and the exit of the sixth nerve; a small hole terminating the aqueduct of the cochlea ; and, lastly, a rough surface for the attachment of the internal peristaphylinus, and the external muscle of the malleus. At the line of junction between this plane and the posterior is generally seen part of the groove for the inferior petrous sinus. (Plate XXVI. fig. 3.)

The circumference is united behind by a serrated margin with the occipital bone; above by a margin, partly serrated, partly imbricated, with the parietal bone and posterior part of the large wing of the sphenoid; and before and below by a serrated margin with the lower part of the same wing. This part, named generally the squamous, forms with' the pyramid a re-entrant angle, in which is received the spinous process of the sphenoid bone; and close beside which is the orifice of the Eustachian tube (iter a palato ad aurem), the canal which leads from the throat to the tympanal cavity. The truncated extremity of the pyramid, which is received by the re-entrant angle formed by the sphenoid and occipital bones, presents the upper opening of the carotie canal, which is imperfect above, and in the recent body is completed by the dura mater.

The temporal bone is thin before and above, where it consists of two tables with intermediate diploe. The mastoid process in the adult consists of numerous communicating cells, lined by very delicate periosteal mucous membrane, continued from the tympanal cavity, with which they communicate. The pyramidal portion is compact and hard, and contains with other parts the labyrinth or internal ear.

Nothing is more interesting than the developement of [7:2:776]the temporal bone. It is ossified in three portions,—the large, flat, or squamous; the tympanal ring; the pyramidal, with the mastoid, and the styloid process.

At an early period the pyramidal portion is perfectly formed round the several soft parts, and though porous and spongy, dense bone is seen in the site of the semicircular canals. The different orifices are large and distinct. The tympanal cavity, however, is quite incomplete; and though the carotic canal is formed, the Eustachian tube is in the shape of a mere groove. The size of the pyramid is greater than subsequently in proportion; and the part behind the open tympanal cavity, which is bulky, is to constitute the mastoid process, which however is still a shapeless mass. The squamous portion is thin and almost sealyat birth, with the zygomatic process well marked, and a ring of bone, incomplete at the upper margin, attached to its inferior and posterior part. By this, which afterwards constitutes the ring of the external .ear-hole, it is fixed to the pyramidal portion in such manner that the part behind the ring is rather larger and longer than the part before; and the pyramid, instead of projecting, as afterwards, is short and thick. At this period also the flat portion uniting with the occipital bone is not formed, and there is therefore an opening or fontanelle at this point of the cranium. Soon, however, the squamous becomes united with the pyramidal portion; the tympanal ring is fixed to both; the Eustachian tube is completed; and, at the posterior end of the pyramid, bone is deposited and extended in a tabular layer of some thickness. The mastoid process, however, cannot be recognised; and it is only some years after birth (about seven) that a small oblong elevation begins to be visible behind the posterior limb of the auditory ring. If at this time the process is divided, cells of the kind afterwards seen in this part are not distinct; but as its enlargement proceeds, cells begin to be formed about the same time, and at the same rate, as the frontal, ethmoidal, and sphenoidal cells are formed. The figure of the bone also is altered, in consequence of the change which the component parts undergo in relation to each other. The squamous portion expands, the anterior part of the pyramidal portion is elongated and tapers, the posterior and the mastoid parts enlarge, and at a later period the styloid process begins to appear amidst the muscles attached to it.

The temporal bone is united immovably with the sphenoid, parietal, occipital, and malar bones; and the inferior maxillary is connected to it by articulation. In the tympanal cavity, also, are contained the four tympanal bones, to be considered afterwards.

Besides these uniform bones of the cranium, there are occasionally found one or more supernumerary bones, which vary much in number, size, and situation. Most usually they are found in the line between the occipital and parietal bones, causing the lambdoidal suture to vary much in regularity; and occasionally, instead of the apex of the occipital bone, is found a single supernumerary bone. They are observed less frequently at the inferior anterior angle of these bones, and at the temporo-parietal sutures, and still more rarely at the base of the cranium. These bones, to which attention was originally drawn by Wormius, by whose name they are still distinguished (ossa Wormiana), may be regarded as effects of the aberration of the ossifie process. Though they have been also named triangular (ossa triquetra), their shape is extremely variable. They are similar in structure and mode of union to the parietal and occipital bones; and though they are not entitled to the epithet of cranial keys (claves cranii), often given them, they may be viewed as appendages to the cranial bones, which are then to be regarded as incomplete. The most important fact in their history is, that they are most frequent in young subjects, and in those in whom ossification is imperfect. As they are rarely found in advanced age, it may be inferred that they eventually become consolidated with one or other of the bones to which they adhere.

§ 5. The Face. (Ossa Faciei.)

The face, situate before and below the cranium, is bounded above by that cavity, on the sides by the zygomatic arches, and behind by a space corresponding to the upper region of the pharynx. Symmetrical in disposition, its anterior surface is trapezoidal, the largest side being above, its vertical section triangular, and each side irregular. The bones of which it consists are those of the upper jaw, comprehending thirteen separate pieces, two superior maxillary bones, two malar bones, two nasal bones, two lacrymal bones, two inferior turbinated bones, two palate bones, and one vomer; and the single lower jaw. (Plate XXVI. fig. 8.)

The superior maxillary bone (os make, maxilla superior) ' is the basis of those of the upper jaw, and forms a centre,J with which the others are connected. Though in shape irregular, it may be distinguished into zygomato-facial, orbitar, and naso-palatine surfaces. (Fig. 6.)

The zygomato-facial surface, irregularly convex and concave, consists of two divisions, the facial and zygomatic. The first presents the nasal or ascending process, terminating above in a serrated margin, articulated with the frontal bone; behind in a groove concurring with a similar one in the lacrymal bone to form the lacrymal canal; before by a similar margin joining with the nasal bone; and below, a pit for the insertion of the levator of the upper lip and nose (levator labii superioris aloeque nasi). The facial surface below this, bounded on the mesial side by a sinuous hollow, the nasal, and a spine forming with that of the opposite side the nasal spine, presents above, the superior maxillary hole for the exit of the second branch of the trigeminal nerve, the canine fossa for lodging the levator anguli oris, separated by an elevation from the incisive fossa for lodging the myrtiform muscle (depressor alee nasi). The facial region is separated from the zygomatic by a rounded margin, the upper extremity of which is rough and hollowed for articulation with the malar bone (os genae, os jugale) ; while the posterior forms part of the temporal fossa before, and a distinct protuberance behind corresponding to the posterior part of a large cavity denominated the maxillary (antrum maxillare, sinus maxillaris). This cavity, indeed, corresponds also to the canine fossa and the external protuberance.

The orbitar surface, which is flat, and slightly oblique in direction, forming the inner half of the lower wall of the orbit, is bounded within by a sharp line for articulation with the ethmoid bone, without by the rough malar surface, and traversed through its posterior half by a groove for the maxillary vessels and nerve, terminating partly in the sinus, partly in the superior maxillary hole. The posterior margin of this surface, which is obtusely rounded, forms with the sphenoid bone the spheno-maxillary fissure; and its internal or mesial angle is articulated with the ascending process of the palate bone.

The naso-palatine or mesial surface of the bone is complicated. Before and above is seen the inner surface of the nasal or ascending process, traversed by vascular and nervous grooves, and covered by the pituitary membrane. Behind this is the lacrymal groove, terminating in the nasal, which is converted into a canal by the inferior turbinated bone, below which it opens; and the open [7:2:777] ing into the maxillary sinus, large in the detached bone, but contracted below by the inferior turbinated, and behind ʹ by the palate-bone. This sinus, which is of an irregular tetrahedral shape, corresponds before to the canine fossa, behind to the zygomatic tuberosity, above to the orbitar plate, and below to the alveolar arch. Below this is the palatine plate (apophysis palatina), quadrilateral and horizontal, concave and smooth above, where it forms the lower wall of the nostrils, concave and marked by vascular orifices below, where it forms the anterior part of the hard palate. (Fig. 7.) The anterior part of the process is elevated into the nasal spine; its mesial margin, which is thick and marked by numerous grooves, one unusually large for the naso-palatine nerves and vessels (canalis incisivus vel Stenonianus), is joined to that of the opposite side, forming a groove in which the lower margin of the vomer is received; and the posterior, which is thin, is attached to the square plate of the palate-bone, which thus completes the palatine vault.

The palatine is separated from the zygomato-facial region by a semiparabolic arch, perforated in the adult by eight honeycomb-like pits (alveoli'), in which the roots of the teeth are implanted, and therefore named the alveolar arch. Of these pits the first two are the smallest, the next three larger, and the last three very large,—an arrangement which renders the alveolar arch narrow before, and broad on the sides and behind.

The superior maxillary bone is united, at the points indicated, to that of the opposite side, to the frontal bone, to the ethmoid, to the nasal, to the lacrymal, to the palatine, to the malar, to the inferior turbinated bone, and to the vomer.

It is ossified in one piece. In the foetus its divisions are completely formed, except the orbitar plate, the sinus, and the alveoU. In the former, the superior maxillary canal is a slit; and the latter is a mere depression on the nasal surface of the bone. This, however, becomes larger and more capacious, not by excavation, but by the extension of its walls by bony deposition. The alveolar arch in general consists of two parabolic plates united by transverse septa, so imperfect, that the whole intermediate groove communicates freely. These osseous plates are not uniform in number. In some maxillary bones there are four, and a fifth like a mere line at the bottom of the groove; in others six alveoli, viz. four temporary, and two permanent alveoli. These plates are formed by deposition round the dentiferous sacs.

The malar bone (os jugale, os genae) is a quadrilateral bone, approaching the rhomboidal shape, but bounded by curved lines. It presents three surfaces, a facial, an orbitar, and a zygomatic; and four angles, a frontal, a temporal, a zygomatic, a superior maxillary, and an inferior maxillary. (Fig. 7 and 8, g.)

The facial surface is convex and smooth, marked by one or two holes (foramen jugale) for vessels and nerves, and, with the zygomatic process gives attachment below to the zygomatic muscles.

The orbitar surface, which is concave, directed obliquely upwards, projects backwards from the facial plate, and forms the outer wall of the orbit between the frontal and sphenoid bone above, and the superior maxillary below. It presents the internal malar hole, or the inner orifice of that seen in the facial surface. The posterior edge is rough and serrated for conjunction with the sphenoid bone.

The zygomatic surface is a sort of angular concave recess between the orbitar plate above and the facial before, and is chiefly important in forming the anterior part of the temporal fossa. In the angle between the orbitar and facial plates is seen a small hole, which communicates with the internal malar above, and the external malar before. The anterior part of this surface is rough, and unites with the external or malar process of the superior maxillary bone.

The superior or frontal angle is serrated for uni tin g with the external angular process of the frontal bone. The temporal is long and pointed, and rough above, where it joins the temporal bone to form the zygoma, to which the temporal fascia above and the masseter below are attached. The superior maxillary or orbitar is also pointed, and joins the rounded ridge at the base of the ascending process of the superior maxillary bone. The inferior maxillary is obtuse-angled, and joins the lower angle of the malar process.

Wedged between the bones of the scull and face, the malar bone is connected to the frontal, the temporal, the sphenoid, and the superior maxillary. It is ossified from a single point.

Each nasal bone (os nasi) is quadrilateral and trapezoidal. Of its two surfaces, the external, smooth and slightly convex, is covered by the periosteum and the pyramidal muscle (compressor narium) and part of the frontal (epicranius). The inner, rather concave and somewhat irregular, with grooves for vessels and nerves, is covered with the pituitary membrane. (Fig. 8, n.)

The upper margin of the nasal bone, which is somewhat thick, is serrated for union with the frontal bone, on the nasal spine of which it is firmly supported. By the mesial margin, which also is thick, plain, and prolonged backwards, it is joined to that of the opposite side; while its thin external margin being imbricated beneath the mesial one of the maxillary, the central pressure is thus opposed on each side. In this manner the two nasal bones, supported above by the frontal spine, are firmly wedged between the superior maxillary, much on the same principle as the key-stone is wedged between the lateral parts of the arch. (Plate XXIV. 2 and 3, n.) To the lower margin the nasal cartilages are attached. Each nasal bone is formed from a single centre of ossification.

Each lacrymal bone (os lacrymale, os unguis) is about the size of a nail, situate at the inner wall of the orbit, occupying the space between the frontal bone above, the ethmoid behind, and the superior maxillary before. Its shape is irregularly quadrilateral, and it presents two surfaces, an orbitar and nasal, and four margins.

The orbitar surface consists of two regions, one orbitar proper, flat, and smooth, situate behind, and connected with the lateral smooth bone (os planum) of the ethmoid, with which it completes the inner wall of the orbit; the other, which is anterior, is at right angles to this, and is moulded into a cylindrical groove, which, with that of the superior maxillary bone, constitutes the lacrymal canal, in which is lodged the membranous tube which conveys the tears and mucus from the eye to the nose. These two surfaces are parted by a sharp longitudinal crest, to which is attached the aponeurosis of the orbicular muscle of the eyelids (orbicularis palpebrarum).

The nasal surface is irregular, covered by the fibro-mucous membrane of the ethmoid cells, and of which it makes part. It presents distinctly the angle of union between the orbitar and lacrymal portion of the bone.

This bone, which is compact, is developed from a single point, and is early formed in the foetus.

The inferior turbinated bones, which are irregular in' shape, are attached to the nasal surface of the superior ' maxillary by an oblique line near the lower margin of the ’ antrum, with the convex surfaces turned to each other.

Each turbinated bone presents a nasal surface, uneven and marked by rough lines, with intermediate cellular [7:2:778]grooves; and a maxillary one, concave, and constituting part of the inferior nasal passage. Both are invested by fibro-mueous membrane continued from the pituitary.

Each turbinated bone is bounded by two margins,—a superior, which is fixed,—an inferior, free. Of the former, the anterior part is a thin border, joining with the superior maxillary bone at the base of the ascending process, and with the laerymal bone by an angular slip. The middle is a short spinous part, uniting with the lateral mass of the ethmoid, and diminishing the opening of the maxillary sinus; and the posterior part, which is rounded and inclining, is attached to the crest of the palate-bone. The lower margin, which is free, is slightly convoluted on itself, so as to separate the middle from the inferior nasal passage.

The inferior spongy bone, which is formed in one piece, though perforated by vascular and nervous holes, and moulded into cells at its lower convoluted margin, consists, however, chiefly of compact bone. It is covered through its whole extent by the fibro-mucous membrane of the nasal passages.

Each palate-bone (ossa palati), attached to the posterior part of the superior maxillary bones, to which they may be regarded as appendages, consists of three parts, a base or palatine portion, a nasal ascending or vertical portion, and an orbitar part.

The base consists of a quadrangular and quadrilateral plate of bone, placed horizontally, and attached before to the posterior margin of the horizontal or palatine plate of the superior maxillary bone, and on the inner or mesial side to the corresponding margin of the opposite bone (Plate XXVI. fig. 7, p, p), with which it forms a groove, in which is lodged the posterior part of the lower margin of the vomer. The upper surface is concave, and, with that of the superior maxillary bone, completes the lower wall of the nasal passages. The lower is almost straight, but presents a slight concavity, bounded behind by a transverse crest of bone, to which the uvula or soft and movable palate is attached. Behind this is a surface bounded by the posterior margin, which is sinuous and lunated, and terminates within in a pointed eminence, which, with that of the opposite side, forms on the mesial plane the palatine spine. The external margin, which rises into the nasal or ascending portion, is rounded without into a sinuous depression, which forms, with the pterygoid process of the sphenoid bone, the pterygo-palatine canal, and which occasionally, at least at its lower extremity, is entirely formed in the palate-bone.

The nasal portion, which is irregular in shape, presents on the na∙sal surface a hollow, rising from the square plate, and forming the posterior part of the lower nasal passage; a transverse ridge (linea aspera) continuous with that of the superior maxillary bone, and to which the inferior turbinated bone is attached; and then another hollow, forming the posterior end of the middle nasal passage, and with the former contracting the orifice of the maxillary sinus. Immediately above this the vertical portion is parted by a notch into two unequal parts, a posterior articulated with the base of the external pterygoid process, and an anterior articulated before with the superior maxillary bone, and within presenting cells, which unite with those of the ethmoid bone. The outer part of this cellular portion is bounded by three surfaces, one external, forming part of the zygomatic fossa ; another anterior, resting on a corresponding surface of the superior maxillary bone; a third superior, forming part of the inner wall of the orbit. The notch between the anterior and posterior divisions forms with the sphenoid bone the spheno-palatine, for transmitting the spheno-palatine twig of the superior maxillary nerve, with some veins, and the internal branch of the spheno-palatine ganglion.

The posterior margin of this vertical portion is acute above, where it is simply conjoined with the base of the pterygoid processes; but below it is moulded into a thick, strong, triangular process, projecting backwards, and marked by three grooves, one in the middle, and one on each side. In the two latter the external and internal pterygoid processes are adapted; and the middle space, being prominent, and firmly wedged between the pterygoid processes, completes the pterygoid fossa.

Each palate-bone is connected with six bones, two of the cranium and four of the face; the ethmoid and sphenoid, the superior maxillary, the inferior turbinated bone, the palate-bone of the opposite side, and the vomer.

The palate-bone, so far as is hitherto observed, is formed in one portion. In the foetus, at the seventh month, it is completely formed; but the square or horizontal part is larger in proportion than the vertical, and remains so till the face begins to alter its shape.

The vomer or plough-share bone is symmetrical, placed on the mesial plane between the sphenoid and ethmoid bones above, and the palate and superior maxillary bones below, and forming the posterior part of the nasal partition.

In shape it is irregular, though it affects the rhomboidal. It consists of two thin plates of compact bone united at an angular line below, but separated above so as to form a deep longitudinal groove, in which the cartilaginous partition before, and the vertical plate of the ethmoid behind, are inserted. At the posterior end these plates spread out into lateral wings with intermediate grooves, in which the azygos process of the sphenoid bone is accurately fitted. These two parts form the upper and posterior margins. The lower consists of a single thin plate, which is received into the linear groove formed by the middlecrest of the palate and superior maxillary bones. The anterior part of this margin rises more directly, to fit the nasal spine of the latter bones.

The surfaces of the vomer are smooth, occasionally concave and convex in opposite directions, and, being covered by the fibro-mucous pituitary membrane, constitute the bony partition between the right and left nasal passages. The bone is formed in a single piece, and is generally completed in the seventh and eighth month.

The lower jaw-bone (mandibula, maxilla inferior), symmetrical, placed at the base of the face, is of a shape, nearly parabolic, with an elevated branch at each extremity. It consists of two parts, a maxillary arch, and a ramus at each end, each of which has two surfaces, an external or facial, and an internal or oral, an alveolar or upper margin, and a mental or lower margin. (Fig. 8 and 9.)

The external surface of the parabolic or arched portion of the lower jaw presents first on the mesial plane the symphysis or chin (mentum), indicating the original separation of the bone into two parts,—a vertical line diverging into two, so as to form a triangular eminence (tuber maxillare of Soemmering). (Fig. 8 and 9, x.) On each side of this is a depression for the tuft or levator of the chin, the anterior mental hole (foramen menti anterius, f), or inferior maxillary for the exit of the third branch of the fifth pair, and the external maxillary line (m) for the insertion of the platysma, depressor anguli oris, and depressor labii inferioris. Behind this the ascending ramus presents a quadrilateral surface, corresponding to the masseter (r), bounded before by a sharp line terminating in the coronoid process (b, b), behind by an obtuse one, the posterior margin terminating in the condyloid or articular process (e, c), and above by the sigmoid notch (incisura semilunaris vel sigmoidea) between them. .
[7:2:779]

The internal or oral surface of the lower jaw presents in the middle a spine or crest (spina menti interna), consisting in general of three eminences, the two superior of which give attachment to the genio ∙glossi, and the lower to the genio-hyoidei. On each side of this is a superficial hollow for the sublingual gland, and a pit for the digastric muscle; and extending outward on each side is the internal oblique line, to which the mylo-hyoideus and the superior constrictor of the pharynx are attached. Below this is a depression for the submaxillary gland; behind, at the margin of the ramus, the surface is rough for the insertion of the external pterygoid; between this and the top of the oblique line is the internal mental hole, or the inner orifice of the maxillary canal; and above and round the orifice the surface is rough for the insertion of the internal ligament of the lower jaw. By this orifice the inferior maxillary nerve, or third branch of the fifth pair, with its concomitant vessels, enters the canal; and after sending branches to the alveolar arch and membranes, reappears at the external mental hole.

The upper margin of the parabolic part of the bone is moulded into a series of alveolar or honeycomb-like cavities, bounded by external and internal plates, and separated by septa more or less complete. These cavities are in the adult 16 in number, but are sometimes imperfect, sometimes obliterated by the removal of the teeth. This margin, which, like the corresponding one of the superior jaw, is named the alve'olar arch, is, like it, narrow anteriorly, and wide on the sides and behind. At the posterior end of each alveolar arch the external and internal oblique lines form between them a superficial depression, in which part of the buccinator is lodged; and then converging as they ascend, terminate in the pointed coronoid process, to which the tendon of the temporal muscle is fixed, unless at its outer surface, which is covered by the masseter. The condyloid process, separated from this by the sigmoid notch, is broad transversely, and is contracted below so as to form a neck, which is concave within for the insertion of the external pterygoid muscle.

The inferior margin, which is obtusely rounded, and forms a more pointed curve than the upper, gives attachment only to the cutaneous muscle (platysma myoides). The posterior margin, also obtuse, is free, but corresponds to the parotid gland, and is therefore occasionally named the parotid margin. To this the stylo-maxillary ligament is attached.

The posterior part of the bone, named the ramus, forms with its body an obtuse angle of about 100°, which diminishes as life advances. (Fig. 8, a, r.)

The inferior maxillary bone is connected movably with the temporal bone by its condyloid process being lodged in the glenoid cavity of the latter. In this situation it is retained by means of three ligaments, while its motions are facilitated by an interarticular fibro-cartilage.

The external ligament, composed of parallel fibres attached to the tubercle at the bifurcation of the zygomatic process, descends obliquely backwards, and is fixed to the outside of the neck of the condyle of the lower jaw. It is covered by skin and the parotid gland, and is lined by synovial membrane, to part of which the interarticular cartilage is attached. The internal ligament, attached to the spinous process of the sphenoid bone and its vicinity, proceeds obliquely downwards and forwards, between the two pterygoid muscles, expanding, to the orifice of the internal maxillary hole, round which it is attached.

The stylo-maxillary ligament is an aponeurotic chord, belonging rather to the stylo-glossus muscle, stretching between the styloid process and the tip of the angle of the lower jaw, where it is inserted between the masseter muscle without, and the internal pterygoid within.

This articulation is so constructed that it possesses two synovial membranes, or at least a double one, the parts of which are separated by the interarticular cartilage. The latter body, which is of an oval shape, convex and concave above, to fit at once the glenoid cavity and the transverse process, but concave below for the maxillary condyle, adheres externally to the external ligament, while its inner margin is free. The upper division of the synovial membrane, therefore, adhering all round to the margins of the glenoid cavity and transverse process, after covering these parts, is reflected from the external lateral ligament over the upper surface of the interarticular fibro-cartilage. A minute slip may be then traced over the free margin of this fibro-carti]age, covering its lower surface, and thence continued over the inside of the external lateral ligament, and from it over the condyle of the lower jaw. In this manner the temporo∙maxillary synovial membrane is rather composed of two parts, a superior and inferior, than absolutely double.

The inferior maxillary bone is formed in two pieces; and perhaps no bone in the human body undergoes from first to last greater changes in shape and extent than it does. In the foetus, when first formed, it consists of two slightly incurvated portions, united on the mesial plane by cartilage, with the coronoid and condyloid process, and the intermediate sigmoid notch, rising from the posterior extremity of each. The ramus, however, cannot be said to be formed; and it is only some time after birth that the quadrilateral surface by which it is defined can be recognised. At birth, also, the alveolar arch consists only of two thin plates of bone, with scarcely perceptible traces of septa ; and the periosteal coverings of the dentiferous sacs are in immediate contact with each other. After birth, bone is deposited between them, so as to form the transverse partitions of the alveoli, which afterwards increase in size and thickness with the bone itself, which enlarges in all its dimensions chiefly by extending backwards. Coalescing by the progress of ossification on the mesial plane, it is a few weeks afterbirth consolidated into one bone; and after the process of primary dentition commences, it loses the angular and acquires the parabolic shape. About the age of seven, sometimes previously, the body becomes more incurvated, and the posterior extremities enlarge backwards still more rapidly. As the process of secondary dentition advances, these extremities enlarge still more rapidly; and the angle of the jaw acquires a more prominent situation by becoming more depressed. At the time at which the facial and maxillary sinuses are formed, and the superior maxillary bone extends backwards to form its tuberosity, the posterior extremity gradually rises in the form of the ramus, till this part a year or two after puberty is fully an inch above the plane of the alveolar arch. During adolescence and middle life this is the condition of the jaw-bone. Towards the decline, however, the teeth drop out, and the alveolar processes are absorbed; and in old age the lower jaw consists often of a single cylindrical arch of bone placed between its two rami, which, retaining their original breadth and height, necessarily throw the body of the bone forwards beyond the upper alveolar arch.

The lower jaw-bone consists of two plates of compact bone, with cancellated tissue interposed, and traversed by the inferior dental canal, the walls of which, like the surface of the bone, are compact. This canal is subdivided into two parts,—one inferior, which terminates in the anterior mental hole, transmitting the mental branch of the inferior maxillary nerve; the other superior, which is parted into numerous minute passages into the cancelli of the bone and alveolar processes. These, it must also [7:2:780]be observed, consist of a peculiar form of cancellated structure. Externally their bony walls are perforated by numerous minute well-defined holes, into which, in the recent state, the vessels and filaments of the alveolar periosteum penetrate. These orifices are so numerous in both maxillary bones, that a portion of alveolar process held between the eye and the light seems entirely perforated, and, if injected, becomes completely red. This character applies chiefly to the period of youth and adolescence. After this the alveolar processes become more solid, and eventually present much fewer orifices. This structure is the result of the manner in which the bony matter is deposited round the vessels and filaments of the periosteum, which may in this and similar bones be said to communicate in this manner with those of the medullary membrane.

The Teeth. (Dentes.)

The teeth, which are implanted in the alveolar cavities, though belonging properly to the digestive apparatus as organs of mastication, are nevertheless more conveniently considered in this place. (Plate XXVI. fig. 7, 8, and 9.)

In every tooth are recognised three parts,—the crown (corona), the neck or collar (collum), and the root (radix). The first is the portion which appears above the gum and alveolar process, and consists of a layer of enamel, thick above and round the top, but gradually extenuated below, inclosing a small portion of compact bone. The crown may be distinguished into the crown proper, or the summit or apex of the tooth, and the fillet or annular portion of enamel (annulus) by which the sides are surrounded. The root, which consists of compact bone, is the part which is implanted in the alveolar cavity, and the outer surface of which adheres to the inner or dental surface of the alveolar periosteum, and above that to the soft part of the gum. The neck is the narrow ring where the enamel ceases and the bone begins, and to which the gum adheres all round. This part, in short, belongs neither to the crown nor to the root, and perhaps is not justly entitled to any separate consideration, unless as the portion to which the gum adheres. The crown and root, on the contrary, are important, as furnishing the characters by which the teeth are distinguished into classes.

These are three,—the incisor or cutting teeth (dentes tomici, incisores, primores, risorii, acuti, adversi) ; the canine or tearing teeth (dentes canini, laniarii, cuspidati) ; and the molar or grinding teeth (dentes molares).

The incisors are in number eight, four in each jaw, and two on each side of the mesial plane. All of them agree in having the crown or apex wedge-shaped, or like a carpenter’s adze, convex before, and slightly concave behind, with the cutting edge crenated or notched. From the edge, also, which is broad, the fillet, which is quadrilateral, contracts much to the neck, and the root is bevelled in the opposite direction to that of the crown, so as to form a quadrilateral prism, and slightly acuminated. It is always simple and elongated. Its extremity presents an orifice communicating with the interior of the tooth, and admitting the vessels by which it is nourished. The crown is separated from the root by a narrow line, varying in position in the different kinds of incisors.

The incisors of the upper jaw are broader, thicker, longer, and in general more powerful, than those of the lower, and their axes are directed downwards and forwards so as to overlap in the motions of the lower jaw those of the inferior row, and leave a triangular interval with the base upwards. Their cutting edge also is oblique, so that its mesial angle is longer than its external; and their roots are larger and rounder. The central or middle incisors are larger, broader, and stronger, than the lateral ones.

The incisors of the lower jaw are smaller than those of the upper, and their axes are directed upwards and backwards, so that they are within the superior incisors. The central incisors also are larger than the lateral ones.

The canine or pointed teeth (dentes cuspidati) are four in number, one in each half of each alveolar arch, immediately next to the lateral incisors. These teeth are distinguished by prominent, thick crowns, with rounded convex fillets and pointed apices. The root also, which, like that of the incisors, is simple, is larger and thicker than in the latter. The upper canine teeth, which occasionally are named eye-teeth (ocularii dentes), are the longest and most prominent of all. During the elevation of the lower jaw, each inferior canine tooth is interior to the superior one, and is interposed between it and the lateral incisor.

Of die molar or grinders there are 20 altogether, being five in each half of each alveolar arch. They are subdivided into two orders, small molar or bicuspid teeth (dentes bicuspidati), and large molar or multicuspid teeth (dentes multicuspidati).

The molar teeth agree in having large, broad crowns, with tubercular summits, and roots, which, though occasionally single, are much more frequently two-fold, threefold, or four-fold. The coronal tubercles are generally parted by a deep furrow, which gradually becomes shallow as the summits wear in the progress of years. When the roots are single, which is most frequent in the bicuspid order, each lateral surface is marked by a longitudinal furrow. When two-fold or manifold, they are parted by a fissure of variable width; and sometimes they diverge considerably. The annular furrow between the crown and root is very distinct.

The axes of the upper molar teeth are directed outwards, while those of the lower order, especially the most posterior, are directed inwards. More anteriorly they are occasionally vertical.

The two molar teeth next to the canine, which have smaller crowns and roots, and are less in all their dimensions than the three posterior ones, are therefore distinguished as small molars. From the circumstance of their crowns being provided with two conical apices, one anterior, large, and the other posterior, parted by a transverse furrow, not dissimilar to the summits of two canine teeth conjoined in one, they were denominated by John Hunter bicuspid teeth (bicuspidati). These teeth are smaller than the canine, especially when their roots are single. The roots, however, are often biful, and sometimes triful. In the first case they are bevelled on the sides, and terminate in a point. In the second and third case they are conical. The internal surface of the bicuspid teeth is very generally narrower than the external, so that a transverse section would be trapezoidal, with the narrow margin posterior.

The third molar tooth, or the first large molar, is generally very large and strong, with the crown broad and quadrilateral, surmounted by four, five, or more tubercles, and: the root triful or quadriful and divergent in the upper tooth, more frequently biful only and divergent in the lower. The second large molar tooth, though rarely so large as the first, has the same general shape; the crown rhomboidal in the upper jaw, with four apices, and the root biful or triful and divergent.

The third large molar, named also wisdom-tooth (dens sapientice), from its late appearance, is smaller than the second, generally has a narrower crown, rounded, oblong, [7:2:781] quadrilateral, or rhomboidal, with two or three apices, and a narrow root generally single and conical, often in- ' complete. Its axis is strongly directed inwards, especially ‘in the upper jaw.

The orders of teeth now enumerated constitute arches of a parabolic or semielliptical shape, larger in general in the upper jaw than in the lower. In the upper arch especially, the curvature is more rounded or elliptical; in the lower it is more angular and parabolic,—a circumstance which, with the different directions of the axes of the incisor and molar teeth respectively, causes the upper incisors to overlap, and thereby cut upon the lower ones, while the molars are fitted to each other so as to move on mutual surfaces in the lateral motion of the jaw.

The teeth vary in number, shape, and position.

Though the general number of the adult or permanent teeth is 16 in each jaw, or 32 in all, it may happen that, in consequence of all the wisdom-teeth not coming through the gum, there are only 28 or 30. Occasionally also the lateral incisors are wanting. In some rare instances there is a supernumerary incisor or molar tooth; and Soemmering mentions an instance in which, by the addition of four molar teeth, the total number was augmented to 36. The union of two or more teeth into one is occasionally observed.

The most usual variations in shape are observed in the incisors being excessively large and broad, in the canine being very thick and long, ascending into the antrum, and in some rare instances extremely small. In females the canine teeth are occasionally so small and rounded, that they have the appearance rather of rudiments than of perfect teeth. The cleft roots of the molar teeth are liable to very great varieties in shape.

The most usual variety in position is when the incisors are placed obliquely, with their margins not lateral but antero-posterior. This is in general the result of the teeth being too much crowded in a small alveolar arch; and the malposition is always greatest as the jaw is narrow, or imperfectly formed. One or two incisors even in such circumstances may be entirely behind or before the rest, so as to give the appearance of a double row. The canine teeth are liable to the same change of position; but one greatly more frequent with them is, to be placed so much before the line of the arch as to project considerably forwards, like the tusks of some animals. Another form of this variety is, when teeth appear in unusual situations, for instance the palate or pharynx, or even in the orbit.

The teeth are not at all periods of life the same in number. Generally speaking, at birth, when the teeth have not appeared above the gum, the rudiments of five teeth are found in each half alveolar arch. These, which are to constitute the milk-teeth, the deciduous or temporary, appear above the gum nearly in the following order: the central incisors of the lower jaw about the end of the sixth or beginning of the seventh month; a few weeks after, the central incisors of the upper jaw; after these, the lateral incisors above or below, without determinate order; and between the 12th and 18th months the first pair of molars, either above or below. These are followed by the lower canine teeth, and about the second year by the upper Canine teeth. About the end of the second year, or in the course of the third, the second pair of molar teeth cut the gum; and about the fourth or fifth year in general, the third pair of molar teeth appear. The following table of the periods at which the different classes of temporary-teeth appear, given by Mr Thomas Bell, may communicate a general idea of the succession.

From 5 to 8 months, the 4 central incisors.

From 7 to 10 the 4 lateral incisors.

From 12 to 16 the 4 anterior molars.

From 14 to 20 the 4 canine.

From 18 to 36 the 4 posterior molars.

From these periods, however, there are extensive exceptions; and in no two individuals even of the same family does the same tooth appear at the same period.

About the seventh month the milk-teeth begin to appear above the gum; and about the seventh year they begin to be shed and succeeded by the permanent set. This process begins also in the lower jaw, and advances nearly in the same order: the lower central incisors; the upper, and the lateral above and below; the first pair of molar upper and lower; the second pair of molar above and below; the canine above and below; the third pair of molar; the fourth pair of molar in the eighteenth year; and the fifth pair, or wisdom-teeth, in the eighteenth, twentieth, or thirtieth years.

The average periods of eruption in the lower jaw are given in the tabular form by Mr Thomas Bell, in the following order.

The anterior larger molars 6 į years.

The central incisors 7

The lateral incisors 8

The anterior bicuspids 9

The posterior bicuspids 10

The canine or cuspidati 11—12

The second large molars 12—13

The third large molars, or wisdom-teeth 17—19

Those of the upper jaw are understood to follow these at an interval of two or three months.

In structure the teeth of the human subject belong to the order of simple teeth, that is, consist of bone, invested at the crown by enamel.

The hyoid bone (os hyoides, υ, ossa lingualia), though entirely unconnected with the skeleton, yet as a bone to which are attached various muscles of the throat, must be noticed in this place. It is a bone, or rather a bony apparatus, consisting of five separate pieces, arranged in the parabolic form, and articulated movably with each other. These five pieces are, one middle, two lateral, and two pisiform bones.

The middle (os medium linguce), named also the body, is large, broad, and square, with the anterior surface in general convex and rough, divided by a middle ridge into right and left halves, and by a horizontal line into upper and lower parts, and giving attachment on each side of the middle crest to the digastric, the stylo-hyoid, the mylo-hyoid, the genio-hyoid, and the hyoglossal muscles. The posterior surface is concave and smooth, and covered by cellular tissue, connecting it to the epiglottis. To its inferior margin, which is more extensive and irregular than the superior, are attached externally the sternohyoid, the omo-hyoid, and the thyro-hyoid muscles; and in the middle the thyro-hyoid membrane. To its upper margin the fibres of the hyoglossus are attached. Each of the lateral margins is moulded into a convex cartilaginous surface, articulated with the lateral bones.

The lateral bones (ossa lateralia, cornua), though longer, are less thick than the body. Broad and thick before, with the upper surface concave and the lower convex, narrow behind, they terminate in a round head, tipped with cartilage, to which the thyro-hyoid ligament is attached. At the anterior junction nearly of these with the middle portion, there is attached to the latter on each side a small elongated bone, somewhat hooked. These bones, which seldom exceed the size of a grain of wheat, or rye rather, and which they somewhat resemble in [7:2:782]shape, are articulated to the other two by a true capsular ligament. To their outer surface are attached some fibres of the genio-glossus, and to their upper is fixed the stylo-hyoid ligament.

The hyoid bone consists externally of compact, and internally of cancellated tissue, the latter being most abundant in the middle piece. Though composed in the infant and young subject of five portions, the articulations are invariably obliterated by ankylosis in adult life, and they are converted into a single bone. The junction of the middle and lateral portions is effected first, and that of the pisiform bones afterwards.

The bones now described, excepting the lower jaw and hyoid, are united immovably, or by synarthrosis. The external shape of the cranium is that of an oblong spheroid, or an ovoid, with the small diameter before. Convex in general, it is flattened laterally in the temporal regions, and below in the base. The external surface, smooth and regular above, is marked below by muscular impressions, and penetrated by numerous holes.

The first objects deserving attention are the serrated lines of junction, or what are named the sutures (suturoe), which are in general more conspicuous externally than internally, where indeed they are effaced at an earlier period of life than on the outer surface of the scull. The sutures may be most easily understood by tracing them from the sphenoid bone, which may be regarded as the central point of the cranium.

The first line is that which passes transversely across at the junction of the sphenoid with the ethmoid and superior turbinated bones in the middle, and the frontal bone on each side. Concave in the middle, this line bends backward at each extremity, where it follows the outline of the small wings of Ingrassias. It constitutes the transverse or sphenoidal suture.

The posterior margin of the body of the sphenoid bone is marked by another transverse suture, extremely short, and uniting it with the cuneiform process of the occipital bone. This, which is early obliterated by the indissoluble union of the sphenoid and occipital bones, is a cartilaginous junçtion, afterwards ossified, and, though scarcely entitled to the epithet, is named nevertheless the basilar suture.

A more distinct one is found in the line between the exterior concave margin of the large wing of Ingrassias and the squamous portion of the temporal bone in the spheno-temporal suture. It terminates below at the glenoid fissure, forming an acute angle with a short line between the pyramid and the posterior margin of the spinous process of the sphenoid, named the petrosphenoidal. Above, where it terminates on the parietal bone, a short line, between the outer margin of the large wing of Ingrassias and short spaces of the parietal and frontal bones, is distinguished as the lateral sphenoidal or the spheno-parietal suture.

This line, produced backwards between the upper margin of the temporal and the lower margin of the parietal bone, constitutes a peculiar form of junction, named the squamous suture (sutura squamosa), the temporal, or the temporo-parietal, in which the edge of the former bone is imbricated over that of the latter. In this mode of junction, which is confined to the superior part of the temporal bone, and in which the union of the bones is not secured by dove-tail ossification, but simple imposition, the lateral pressure is effected chiefly by the force propagated from the zygoma and the malar bone.

The posterior part, which is united to the posteriorinferior angle of the parietal, and the anterior-inferior margin of the occipital, presents a serrated line, with alternate indentations, which are well marked, but irregular in size. This, which occasionally presents Wormian bones, may be named the posterior-temporal suture. The descending portion has been distinguished by the name of mastoid suture. Anteriorly, in the base of the cranium, where it passes the jugular notch, the line of junction, which is cartilaginous, is termed the petro-occipital suture.

The sutures now enumerated agree in being found chiefly at the lower region of the cranium, and in securing the junctions of its base. The others to be yet enumerated belong to its superior region, and agree in consolidating and securing the several arches which constitute what may be named the vault of the cranium.

From the point at which the posterior, temporal, and mastoid sutures unite, a serrated line of junction ascends on each side to the common point at which the occipital and parietal bones meet. From the angular junction formed by the two limbs of this suture, it is known under the name of lambdoidal (∆, sutura lambdoidalis) ; and from its situation it is termed the occipital and occipito-parietal suture. By mutual indentations, which are always distinct, it joins firmly the parietal and occipital bones; and it is the most frequent seat of Wormian bones.

From the angle of the lambdoidal suture a similar serrated line proceeds, uniting the two parietal bones on the mesial plane, with equally distinct indentations. The mode in which this stretches between the lambdoidal and coronal sutures, bearing some remote resemblance to an arrow on the drawn bow-string, has procured it the name of the sagittal (sutura sagittalis). In youth and in early life these two sutures are distinct; but in advanced age they are more or less, sometimes entirely, obliterated.

In some craniums the sagittal suture is continued along the frontal bone to the nasal spine, thus parting the bone in two lateral halves. This, which constitutes the proper frontal or median suture, is the remains of the original separation of the bone.

Lastly, Between the frontal bone before, and the parietal bones behind, is seen a serrated line crossing the cranium transversely, the whole breadth between the two sphenoid bones. This, which is named the coronal suture, presents large indentations on each side and small ones in the middle, on the external table, and a converse arrangement on the internal.

By these sutures the bones forming the vault of the cranium are firmly secured; and each bone is made to press against the other so as to augment rather than diminish strength.

The external surface of the cranium may be distinguished into four regions, a superior, an inferior, and two lateral ones.

The superior region, or the vault, is bounded before and behind by the nasal and occipital protuberances, and on each side by the temporal arches. It presents, besides the coronal, sagittal, and lambdoidal sutures, the superciliary arches, the frontal, parietal, and occipital protuberances, and the parietal holes. It is covered by the epicranial muscle and its aponeurosis.

The inferior region or base, which maybe defined from the occipital protuberance behind to the nasal spine before, is free as far as the pterygoid processes of the sphenoid bone, anterior to which it is joined to the bones of the face.

In the posterior portion are seen the occipital spine and muscular impressions, the occipital hole (foramen magnum), the condyloid processes, the anterior and posterior condyloid holes, and the basilar process. Laterally are the digastric groove, the mastoid, styloid, and vaginal pro [7:2:783] cesses, and the stylo-mastoid hole, the glenoid cavity and fissure; the jugular hole (foramen lacerum in basi cranii), separated by a bony process into an internal part for the l nervus vagus and the accessory nerve, and an external for the jugular vein; the pyramid, with the carotic canal, and the anterior lacerated hole between its extremity, the basilar process, and the sphenoid bone, closed by fibro-cartilage in the recent subject. Before these objects, and nearly in the same transverse line, are seen the anterior half of the glenoid cavity of the temporal bone, the guttural orifice of the Eustachian tube, the spinous and elliptical holes of the sphenoid (Plate XXIV. fig. 5), and the pterygoid processes.

• The anterior portion presents the crest or azygos process united with the vomer and ethmoidal plate, the sphenoidal· sinuses, the ethmoidal bone itself, and the nasal spine of the frontal bone; laterally, the anterior surface of the pterygoid processes, the Vidian canal, the round or superior maxillary hole, the temporal and orbitar surfaces of the large wings of the sphenoid bone, the sphenoidal fissure (foramen laceruin), the optic holes, and the small wings of Ingrassias; and, lastly, the vault and internal wall of the orbit, the former by the frontal bone, the latter by the os planum and lacrymal bone.

The lateral regions of the cranium are nearly of an elliptical shape. Each region may be circumscribed by a line drawn from the mastoid process backwards to the union of the temporal and mastoid sutures, then following the semicircular arch of the parietal bone, and the angular arch of the frontal to the zygoma, ear-hole, and mastoid process. The objects inclosed in this region are the posterior mastoid hole, the mastoid process, the ear-hole, and the zygoma, with a large space, defined by the elevated line extending from the posterior extremity of the zygoma upwards to the semicircular arch of the parietal bone, where it is obtuse, and the external angular ridge of the frontal bone, where it becomes acute. To this line, the zygoma, and the malar bone, the fascia of the temporal muscle is firmly attached; the muscular fibres adhere to the bone below as far as the line of the sphenoid bone, and pass downwards under the zygoma. The whole region, though convex in early life, becomes less so in adolescence, and in manhood and advanced age it is flattened and even hollowed.

The internal surface of the cranium, lined by the dura mater, and marked by cerebral and vascular impressions, is distinguished into the superior region or vault, and the inferior or base.

In the former, which is a regular spheroidal concave, the chief peculiarities are, on the mesial plane, the frontal crest, the sagittal groove for the superior longitudinal sinus, pits for the granules of Pacchioni, and the inside of the sagittal suture,. more distinct than the outside; laterally, the upper cerebral regions of the frontal and parietal bones, with their fossae, the coronal suture, and the superior occipital fossae.

The base is more complicated, and is generally distinguished not only into lateral halves, but into anterior, middle, and posterior regions.

On the median line from before backwards, the objects are,—the blind hole (foramen caecum), for the naso-frontal vessels; the ethmoidal crest (crista galli), and vertical plate, with the perforated plate (e) ; the spheno-cthmoi-dal suture; the transverse groove and olivary process, and optic holes (1 1); the pituitary fossa (ephippium) (3); the posterior clinoid processes (4 4); the spheno-occipital junction; the basilar groove for the medulla oblongata (6); the occipital hole; and the internal occipital spine and protuberance. (Plate XXIV. fig. 6.)

Of the lateral halves, the anterior or frontal region is bounded before by an indistinct curved line, formed by the vertical with the horizontal table of the frontal bone, and behind by the sphenoidal arch. In this, which is named the frontal fossa, the anterior lobe of the brain is lodged; while the sphenoidal arch enters the fissure of Sylvius.

Between the sphenoidal arch before, and the posterior margin of the temporal pyramid behind, is contained a cavity shaped like a spherical segment. In this, which may be named the spheno-temporal hollow (fossa spheno-temporalis), the anterior part of the posterior lobe of the brain is lodged. In this cavity also are seen the sphenoidal fissure; the round or superior maxillary hole; the oval or inferior maxillary hole; the spinous or meningeal hole, with the meningeal groove; the anterior or spheno-temporal fissure ( foramen lacerum anterius basis cranii) ; the inner end of the carotic canal; the pyramidal groove; and the semilunar fossa for the Gasserian ganglion. (Plate XXIV. fig. 6.)

Between the temporal pyramid and the internal occipital spine is contained the posterior or temporo-occipital hollow (fossa temporo-occipitalis), which is further subdivided into two cavities, the cerebral above, and the cerebellic below. From the posterior margin of the pyramid to the transverse occipital ridge, a fold of the dura mater, stretched horizontally, separates the temporo-occipital cavity into a superior for lodging the posterior lobe of the brain, and an inferior or cerebellic for lodging the lobes of the cerebellum. In the anterior or cerebellic division is seen the posterior surface of the pyramid, with the internal auditory hole, the orifice of the cochlear aqueduct, the groove for the lateral sinus terminating in the jugular opening, the groove of the inferior petrous sinus, and the mastoid hole and suture. The only object behind is the posterior cerebral fossa, traversed by the lambdoidal suture.

In the foetus the cranial bones inclosed between the pericranium and dura mater, which are thick, soft, and vascular, are incomplete shells not in contact with each other, with prominent and rather thick ossifie centres, from which the osseous radii diverge, and terminate in thin, ciliated margins. At birth, and for some weeks after, though ossification is far advanced, the margins of the bones are incomplete, so as to form the open spaces denominated fontanelles. Of these there are six at the period of birth; the anterior or rhomboidal between the frontal and parietal bones; the posterior or triangular between the occipital and parietal bones; two lateral anterior between the parietal, sphenoidal, and temporal bones; and two posterior lateral between the parietal, temporal, and occipital bones, both of irregular shape. At these points the motions of the brain are distinctly felt.

At the same time the bones have not yet acquired their serrated margins, so that the places of the sutures, which are not yet formed, are occupied by narrow grooves between the cranial bones. As ossification advances, however, their fimbriated margins extend, and mutually meeting, are prolonged so as to be indented into each other by alternate notches and processes. At the same time the bones acquire thickness, so that a distinct space is perceived between the external and internal surface of each. The alternate processes and notches thus acquire firmness, and are immovably dovetailed into each other. In this manner the anterior angles of the parietal bones unite with the frontal, and between the posterior ones the apex of the occipital bone is gradually mortised.

In some instances, however, where the ossifie centre of the original bone appears deficient in energy, or tardy in progress, a new centre may be developed in the line of [7:2:784]junction, while the bones are still much apart. Thus, between the occipital and parietal bones, or between the occipital and temporal bones, may be developed new centres, from which ossification advances, as from the principal points, towards the circumference; and by the successive deposition of bony matter, the margins begin to meet those of the primary bones. The process of mutual indentation takes place exactly in the same manner as with the primary bones; and by this means secondary bones are formed in the lines of the sutures.

The period at which the cranium is entirely ossified varies in different individuals. In general the anterior or fronto-parietal fontanelle, which is the largest, is ossified at the end of the 18th or 20th month, while the anterior and posterior lateral are closed at an earlier period. In some instances, however, between the parietal and frontal bones a small space is left till the 6th or 7th year; and in many persons the part continues depressed and tender for the greater part of life. The sutures are completed at the same time, and are always distinctly formed by the 10th or 11th year. A few years after, they become more consolidated, and, as the bones acquire thickness and density by the compactness of the external and internal tables, are firmly wedged into each other. The spheno-basilar junction generally remains soft and separable till adult age, when by its union the sphenoid and occipital bones are converted into a single piece. Some time afterwards the sphenoid is united with the ethmoid, the two parietals are converted into one, and occasionally one or both are united to the frontal bone. In advanced age many of the sutures disappear entirely, at least in one surface of the cranium, generally the internal first; and the cranium would be converted into a single bone if life were continued sufficiently long.

In shape and dimensions the cranium varies at different periods of life. After ossification is completed in the child, the prominence of the ossifie points, which continue more or less conspicuous till manhood and the formation of the frontal sinuses, gives it a cubo-spheroidal shape. Its section is an oval or two hemispheroidal segments, the anterior being the smallest. At this period the parietal tuberosities and the occipital eminence are prominent, the frontal bone is vaulted, and the high open forehead communicates to the countenance an expression of beauty and simplicity which are always associated with the early and middle periods of life. In the progress of years, however, these prominences become less distinct, partly by the operation of muscular action, partly by the uniform rising and swelling of the margins of all the bones; and the anterior upper and posterior part acquires a uniform spheroidal or vaulted appearance, while the lateral regions are flattened by the action of the temporal muscle. The occipital region also below the spine is flattened, and occasionally excavated; so that while thespine isprominent and unciform, the base is excavated, and overhung by the mastoid processes and the semilunar ridges. The aged scull is thus distinguished by a general rotundity or ovoidal character, unless in the temples, which are flat and hollow; and the convex but occasionally depressed forehead indicates in some degree the transition from youth to age.

The dimensions of the cranium are estimated from its diameters, longitudinal, transverse, and vertical. The first, which extends from the foramen caecum of the frontal bone, is about five inches at an average. The largest transverse diameter, which extends between the bases of the temporal pyramids, is about 4⅜ inches; and a smaller one between the extremities of the two small sphenoidal wings is about 3 inches and 9 lines. The longest vertical diameter, which is between the anterior margin of the occipital hole and the middle of the sagittal suture, varies from 4 inches to 4 inches and 3 lines. From these measurements it results, that the most capacious part of the scull is nearly at the union of the two anterior thirds with the posterior, viz. the level of the occipital hole and basilar groove; and that the ovoidal or oblong-spheroidal is the most general shape. The variations from this shape are found chiefly in the vault, which may be flattened, oblong, cuboidal, or conical.

The Asio-European may be regarded as the best and most symmetrical shape, and to this most of the European crania belong. According to Soemmering, the Belgic scull is the most oblong-globular, the German and Italian spherical, and the Turkish the most spherical of the European. In this country the most usual shape is the oblong-spheroidal, especially among the inhabitants of England. Among an extensive collection of sculls preserved in the Museum of the University of Edinburgh, and believed to be chiefly Parisian, the prevalent shape is the oblong-spheroidal, and the globular, or the general spherical shape, with large transverse diameter approaching to the longitudinal. From the delineations given by Sandifort (Museum Anatomicum, tom. ii.), the English appears most prominent in the occipital region, the French the most vertical forehead, and the Italian most elevated in the vertical region, and most prominent between the parietal tuberosities. The scull of the Swede approaches the cubo-spheroidal, and that of the Russ is distinguished chiefly for the vertical front, considerable transverse width, and large cheekbones. The latter appear not to be peculiar to the Scotish cranium.

Of the Asiatic craniums, the Tartar has the forehead large, not much arched, the occipital region large, the nasal bones descending straight from the frontal, the upper maxillary bone slightly overhanging the lower, and the chin prominent. That of the Calmuc has the vertical, occipital, and parietal regions prominent, the frontal bone and face flattened, the cheek-bones large, and the alveolar arches and jaws broad and prominent. The Mongolian is distinguished by the narrow forehead, flattened and rather depressed glabellar and nasal regions, great facial width between the cheek-bones, and prominent upper jaw.

From the observations of Blumenbach and Soemmering it results, that the ancient Egyptian or Coptic head, as exemplified in mummies,belongs to the European class of craniums. The negro head, on the contrary, is distinguished for its oblique forehead, compressed sides, prominent jaws, general wedged shape, and large size compared with the rest of the skeleton. For more minute information on these varieties, the reader will consult with advantage the work of Soemmering (tom. i.), and the Decades Craniorum of Blumenbach.

In shape the face forms an irregular hexahedron, with a large excavation at its lower region for the mouth and pharynx. Its anterior surface is trapezoidal, with the short side below; its sides trapezoidal, with the short side formed by the posterior margin of the maxillary ramus ; and its upper surface is an oblique parallelogram.

The greatest transverse diameter is between the zygomatic angles of the cheek-bones, varying from 4∣ to 5 inches; its smallest at the symphysis of the lower jaw, from lį to 2 or 2∣ inches; and on the extent and prominence of which depends the general oval shape of the countenance. The height, measured from the glabella to the triangular process of the lower jaw, varies from 4∣ to 4 inches 9 lines.

The direction of the face varies according to the position of the lower jaw. When this is horizontal, the racial plane forms with it an angle of 60°, or deviates 30° from [7:2:785]the vertical plane; and in some tribes, as the negro, this deviation is still greater. A more important character, ' however, is believed to be found by determining the direction of the face in relation to that of the cranium, or ascertaining what Camper denominates the facial angle. This he proposes to fix by drawing one line from the frontonasal protuberance to the spine of the upper maxillary bone,— doe facial (linea facialis) ; another transversely between the external ear-holes; and from the latter a third line (linea horizontalis), drawn at right angles to meet the first. The angle thus formed by the facial and horizontal lines, which is termed the facial, indicates the comparative prominence of the cranium and face. In European heads generally it is about 80°; in the negro it is not above 70°; and in the Mongolian, which is intermediate, it is about 75°. The effect of this angle in giving the countenance intellectual expression, the nearer it approaches to the rectangle, was known to the ancients. In many of the busts of heroes it is almost 90°, and in those of divinities 100°; and as we know that this is much more rectangular than any specimen of the human scull furnishes, it may be inferred that it is imaginary.

It may be further observed, that in the infant the facial angle approaches to 90°, in consequence of the small relative developement of the face. Towards boyhood and puberty, when the face acquires greater size and prominence, it diminishes to 85° and 80° successively. (Cuvier, Bichat.)

The face is subdivided into cranial, facial, zygomatic, and palato-maxillary regions. It is unnecessary to enumerate again the objects found in these several regions; but it is requisite to consider shortly the cavities which are formed by the cranio-facial bones. They consist of the nasal cavities, the orbits, the tympanal cavity, and the palato-maxillary region. These cavities are distinguished by the following circumstances. All of them communicate mutually, and are covered by fibro-mucous membrane, also continuous. In each of them is lodged one of the organs of special sensation; and each communicates with the cranial cavity by openings, through which nerves always, and sometimes vessels, are transmitted. Lastly, these cavities may be regarded as the points by which the cutaneous surface communicates directly with the mucous membrane of the gastro-pulmonary organs.

The nasal cavities (cavum nasale, nares), of an irregular quadrilateral shape, consist of four regions; the upper, the lower, and two lateral. The first is bounded before by the nasal bones, behind by the sphenoidal cells, with which it communicates, and above by the cribriform plate; while its lower limit is a line uniting the inferior margins of the lateral portions of the ethmoid bone. This is parted by the vertical plate of the ethmoid bone into two halves, which are the two superior passages (meatus superior). The lower region is bounded below by the palato-maxillary plate; on the sides by the maxillary, palate, and inferior turbinated bones; above by a plane uniting the lower margins of these bones, and is parted into two by the vomer, which opens before at the nasal notch of the maxillary bones, and behind at the posterior margin of the palate bones. This constitutes the lower passage (meatus inferior), at the anterior extremity of which the nasal canal opens. The anterior part of the region presents on the mesial plane a vertical triangular notch between the middle ethmoid plate above and the vomer below, occupied in the recent subject by the cartilaginous septum of the nose. The middle and lateral regions, which communicate before by this notch, are separated behind by the ethmoid plate and vomer, and are bounded above by the ethmoidal turbinated bone, and below by the maxillary turbinated bone. This constitutes the middle canal (meatus medius), m which the frontal and maxillary sinuses open.

These cavities communicate freely with each other; and their parietes are covered by continuations of the same general fibro-mucous membrane. Their use appears to be to increase the extent without adding to the weight of die facial bones, to afford great superficial extent to the nasal membrane as an organ of smell, and to afford a sonorous vault to the organ of voice.

These cavities, and their appendages, do not exist in the foetus, nor for some time after birth. The ethmoidal and sphenoidal are early formed; and the maxillary sinus begins to be manifest some months after birth. After the primary dentition they enlarge, and rapidly after the second; and towards the approach of puberty, when the maxillary tuberosity is formed, they increase, and speedily attain their natural capacity.

The orbits are two cavities, one on each side of the mesial plane, of the shape of a quadrilateral pyramid, with the apex towards the cranial cavity, and the base anteriorly. Each orbit presents a vault formed by the frontal bone, a floor formed by the superior maxillary, an internal wall formed by the palate bone, ethmoid, and lacrymal, and an external wall formed by the malar and sphenoid bones. The two internal walls are nearly parallel,—an arrangement which renders the axes of the orbits convergent backwards, and indefinitely divergent before. The vault of the orbit is so thin, that a pointed instrument easily penetrates; and a thrust in the e^yeţ is invariably attended with severe, generally fatal, injury to the base of the brain. The base of the orbits is oblique, with the temporal margin behind the plane of the nasal, making the eye more exposed without than on the mesial side. The inner or nasal margin presents the upper orifice of the nasal canal. At the posterior extremity of the inner wall is the optic hole; at the apex is the sphenoidal fissure, which forms nearly a right angle with the spheno-maxillary fissure below; and the floor is traversed by the superior maxillary fissure and canal. The apex of the orbit is occupied by the optic nerve, the third and fourth pair, the ophthalmic branch of the fifth, and the sixth; and the origins of the six muscles of the eyeball, with interposed fat. The base is occupied by the eyeball, surrounded with the tendinous extremities of the muscles, the lacrymal gland at the external region of the vault, and the lacrymal sac in the anterior depression of the nasal margin. To its margins are attached the palpebral and the orbicular muscle. Each orbit communicates with the nasal cavities by means of the nasal duct.

The tympanal cavity, formed in the temporal bone, communicates by the Eustachian tube with the posterior part of the nasal and palato-maxillary cavities. Its further examination belongs to a subsequent head.

The palato-maxillary cavity is formed by the palatine vault above, the alveolar arches and teeth before, by the lower jaw before and laterally, and behind by the basilar process of the occipital bone and the pterygoid processes. It is very irregular in shape, and consists of two regions, the palato-maxillary proper and the pharyngeal. The principal objects deserving notice are the incisive duct in the palatine vault, for the naso-palatine nerves; the pterygo-palatine canal at its posterior angles, for the pterygopalatine branches; and the posterior opening of the nasal cavities. The vault is covered by periosteum and mucous membrane, with the uvula or soft palate suspended at its posterior margin; and the space inclosed by the lower jaw contains the tongue, attached to the hyoid bone, sublingual and submaxillary glands, and is completed by membrane, muscles, and integuments.
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§ 6. The Thoracic Extremities.

The superior or thoracic extremities consist of the shoulder, the arm, the fore-arm, the wrist, and the hand.

The shoulder consists of two bones,—the scapula or shoulder-blade, and the clavicle or collar-bone.

’ The scapula is a triangular bone occupying the posterior part of the chest, having a dorsal and a costal surface, and a superior, a vertebral, and an axillary margin.

The dorsal or posterior surface (dorsum) is divided by a transverse elevated spine into two parts, the fossa supraspinata for the supraspinatus muscle, and the fossa infraspinata for the infraspinatus muscle. The latter is concave above, convex in the middle, and concave towards the axillary or external margin (costa), from which it is separated by a round line or crest for the attachment of the fascia which separates the infraspinatus from the teres major and minor. Between this crest and the axillary margin above is a convex surface, of a triangular shape, with the apex above, for the attachment of the teres minor, and below a flat quadrilateral surface for the teres major.

The spine is a triangular-shaped eminence, rising obliquely from the upper fourth of the dorsal surface; low at the vertebral, elevated at the axillary margin, where it terminates in a broad, flat surface, also triangular, named the acromion or shoulder-top. In the posterior margin of the spine may generally be distinguished two surfaces separated by a ridge. Above the ridge the cucullaris is fixed; below, part of the deltoid is attached; and between is a common aponeurosis. The ridge is biparted towards the acromion, leaving an interval covered by periosteum and integuments only. The anterior part of the acromion presents a cartilaginous facette, for articulation with the acromial end of the clavicle. To its posterior and external margin the deltoid is attached, and to its tip the acromio-coracoid ligament is fixed.

The costal or anterior surface is of a triangular shape, with the apex below, generally concave, but subdivided into smaller spaces by two or more oblique ridges, to which intermuscular fasciae are attached. This surface, which is the subscapular fossa (venter), lodges the belly of the subscapular muscle, the fasciculi of which are interposed between the aponeurotic ridges. Near the vertebral margin is an irregular surface, to which, and also to the margin, the serratus magnus is attached.

The superior margin (costa superior) is thin and pointed behind, where the levator and omohyoid muscles arc attached, and becomes sinuous externally, with a notch converted by a ligament into a hole for the transit of the suprascapular vessels and nerves. The inner or axillary extremity terminates in an elevated hooked process, the coracoid, to the tip of which are fixed the coraco-clavicular ligament, and the united origin of the short head of the biceps flexor and the coraco-brachialis, to the anterior margin the small pectoral, and to the posterior the acromio-coracoid ligament.

The vertebral or posterior margin (costa posterior, basis of some authors) is thin, and ascends straight to the spine, giving attachment to the rhomboideus ; then bends forward, and forms with the superior an angle, to which, as also to the edge now mentioned, the levator is fixed.

The axillary margin (costa axillaris, sometimes inferior) is round and broad above, and narrow below. It presents above, first the glenoid cavity, round at its lower margin, angular above, hollow, covered by cartilage and synovial membrane for receiving the head of the humerus. At the angular point above is a surface for the attachment of the long head of the biceps flexor, and the lower margin presents two tubercular eminences for that of the long head of the triceps extensor. Below this are fixed the teres minor, the subscapularis, and the teres major. The latissimus dorsi, passing over its lower angle, binds it down.

The scapula consists chiefly of compact bone, with little cancellated matter interposed. In the subscapular fossa this becomes completely absorbed, rendering the bone thin and translucent, sometimes perforated. The spine, processes, and angles contain cancellated matter. It is formed from one part for the body of the bone, with epiphyses for the coracoid process and the margins. Nutritious holes are generally found in the angle formed by the spine with the body, and in the axillary margin.

The collar bone or clavicle is a cylindrical bone, alternately incurvated like an f placed at the upper part of the chest, between the sternum and acromion of the scapula. It has therefore two extremities, a sternal and acromial, with intermediate body.

The sternal end is triangular, cartilaginous, concave and convex in opposite directions, surrounded by ligamentous insertions. The acromial end is flattened and recurved, presenting a lunated surface for articulation with the acromion.

The body, with the shape of a triangular prism at the sternal end, is rounded above for the attachment of the clavicular portion of the sterno-mastoid muscle, and presents below a rough surface for the costo-clavicular ligament, and a sinuated line for the subclavian muscle. Towards the acromial end, where it is flattened above and below, it presents before, a surface for the attachment of the large pectoral and deltoid muscles; behind, another for the cucullaris; and below, a prominent oblique crest for the coraco-clavicular ligaments.

Compact in the middle, and cancellated at its extremities, the clavicle is developed from a single point.

The arm-bone or humerus (os brachii) is a long cylindrical bone, divided into head or scapular end, cubital or lower end, and shaft or body.

The head presents three eminences, the articulai· head, the anterior tuberosity, and the external tuberosity. The first, which is hemispherical, incrusted by cartilage and synovial membrane, with the axis oblique to that of the bone, and articulating with the glenoid cavity of the scapula, is separated from the bone by a narrow depressed line named the neck (collum), in which is fixed the margin of the scapulo-humeral capsular ligament. The second is a small, pointed, sometimes biful eminence, to which the tendon of the subscapularis is attached. In the external tuberosity arc distinguished three facettes, to the upper of which the tendon of the supraspinatus, to the middle that of the infraspinatus, and to the posterior the tendon of the teres minor, arc inserted. Between the anterior and the external tuberosity is a longitudinal groove named the bicipital, for the transit of the long head of the biceps flexor.

The cubital or lower extremity is flattened transversely, and moulded into different eminences and depressions. Internally is the inner or ulnar condyle, large and prominent, for the attachment of the internal lateral ligament, and a tendon common to the pronator teres, palmaris longus, flexor sublimis, radialis internus, and ulnaris internus. Externally is the outer or radial condyle, to which are attached the external lateral ligament, and the tendon common to the supinators and extensors, viz. supinator longus and brevis, anconeus, radialis externus, ubuιris externus, and extensor communis. Between these is an articular surface covered by cartilage, moulded into the small head which moves in the cavity of the radius, — a groove corresponding to the margin of the latter; the semicircular crestinterposed between theraíZí’w^andwZw«,—
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another groove rather larger, in which the prominence of the sigmoid cavity is lodged; and the trochlear or pulley-like eminence, which is received in the internal part of the sigmoid cavity, and the size of which renders the inner side of the humerus larger than the outer, and gives it the oblique direction when placed on the horizontal plane. Before is a superficial pit for the coronoid process of the ulna during flexion of the fore-arm, and behind is a deep one for receiving the olecranon during extension.

The shaft is not cylindrical, but prismatic, consisting of three surfaces, bounded by an equal number of lines. The first line, which descends from the anterior tuberosity, and, winding to the side, terminates on the ulnar condyle, is anterior above, where the tendons of the latissimus dorsi and teres major, and the short head of the triceps, are attached, but becomes internal-lateral below, where an intermuscular aponeurosis is fixed. The second, which descends from the fore-part of the large tuberosity to the anterior articular pit, is anterior throughout, and gives attachment above to the large pectoral muscle, at the middle to the deltoid, and below to the brachialis externus. The third line, which descends from the back of the great tuberosity to the external or radial condyle, is posterior above, where the triceps is fixed, but external below, where the intermuscular aponeurosis and the supinator longus are attached.

Of the three surfaces, the first, which is anterior and internal, presents above, the bicipital groove, covered by periosteum and synovial membrane for the long head of the biceps ; in the middle, the medullary hole and insertion of the coraco-brachialis ; and below, a surface covered by part of the brachialis internus. The second, which is external, is covered above by the deltoid, below by the rest of the brachialis, and in the middle presents the deltoid tuberosity for the insertion of its tendon, and below this an oblique sinuosity traversed by the radial nerve. The third, which is posterior, gives attachment above to the triceps, and below is merely covered by that muscle.

The humerus, cancellated at its extremities, and compact in the shaft, is ossified in three parts; one for the latter, and one for each of the former.

The ulna or cubit (cubitus) is a long bone placed at the inside of the fore-arm, articulated above with the humerus, below with the carpus or wrist, and laterally with the radius. Its superior or humeral extremity consists of two eminences, and an intermediate semilunar or crescentic cavity. The first is a large head named the olecranon (ωλίνης χeαvοι>, ulnae caput, or elbow; processus anconeus, αneon) ; irregular above, with a small space behind, where the tendon of the triceps extensor is fixed; concave and cartilaginous before, where it forms part of the sigmoid cavity. The second is a broad, thin-edged process, prominent before, about half an inch below the olecranon, the upper surface of which is cartilaginous, and completes the sigmoid cavity; the lower surface is rough for the braclùalis internus, some fibres of the pronator teres, the flexor sublimis, and the internal ligament of the humero-cubital articulation. At the outside, and continuous with the sigmoid cavity, is a small semicircular cartilaginous surface—the small semilunar — for articulating with the head of the radius.

The lower or carpal extremity presents a cartilaginous surface, shaped like a circular sector, the circular margin being bent upwards, so as to form a circular surface for the inner articular surface of the radius, while from the centre of its radii arises a pointed process named the styloid, to the tip of which the external ligament of the radio-carpal articulation is fixed. Between the styloid process and sectorial surface is a depression, to which is fixed the fibro-cartilage of the joint; and behind and without the styloid process is a longitudinal groove for the motion of the tendon of the ulnaris externus.

The shaft has the shape of a trilateral prism, except at the lower extremity, where it becomes cylindrical. Of the three lines by which the surfaces are bounded, the external or radial, which is strongly marked, and sharp at the middle, extends from the posterior tip of the small sigmoid cavity to about two inches above the lower end, and gives attachment to the interosseous ligament. The second, internal or ulnar, which is obtuse, descends from the inner edge of the coronoid process to the inside of the styloid, and gives attachment above and in the middle to the flexor profundus, and below to the pronator quadratus. The third, posterior, obtuse above and below, sharp in the middle, extends from the olecranon to the outside of the styloid process, and gives attachment to an aponeurosis.

Of the surfaces inclosed by these lines, to the anterior, which is concave, and contains the medullary hole, the flexor sublimis is attached above, and the pronator quadratus below. The inner is covered above, where it is broad, by the flexor profundus, and below by the integuments. The posterior or radial is parted by a line into two spaces, to the larger of which are fixed the anconeus and ulnaris externus, and to the smaller the supinator brevis, extensores pollicis longus et brevis, the abductor pollicis, and extensor indicis.

The radius is a long bone, rather shorter than the ulna, forming the outer bone of the fore-arm, articulated above with the humerus, below with the carpus, and at the inside with the ulna.

The upper extremity consists of a circular cartilaginous head, concave for receiving the small head of the humerus, with a cartilaginous surface on its inner or ulnar side for articulating with the small sigmoid cavity of the ulna, and a rough one for the annular ligament on the outside. Below this the bone is contracted and forms the neck of the radius, and again swells before into a large rough prominent tubercle, to which the tendon of the biceps flexor is fixed, and which is therefore named the bicipital tuberosity.

The lower extremity, which is double the size, forms an extensive surface for articulation with the scaphoid and semilunar bones of the carpus, continuous on the ulnar side with a small cartilaginous surface for articulation with that of the ulna, bounded without by the styloid process, a rough triangular eminence, to which is fixed the external ligament, and bounded elsewhere by a rough margin for ligamentous insertions. The posterior part of this end presents two eminences inclosing a wide hollow, separated by a small eminence into two grooves,—an inner or ulnar, large for the tendons of the extensor communis and the extensor proprius indicis, and an outer or radial for the extensor longus pollicis. Between the middle eminence and the styloid process are two other grooves,—the anterior for the abductor magnus and the extensor brevis of the thumb, and the posterior for those of the radiales exterm.

The shaft or body, which is thin and round above, prismatic in the middle and below, presents three surfaces inclosed by an equal number of lines. Of the latter, the inner or ulnar descends from the inner margin of the bicipital tuberosity, sharp and prominent, to the small inner articular surface, and gives attachment to the interosseous ligament. To the outer, which descends from the outer margin of the tuberosity, obtuse, to the base of the styloid process, the flexor sublimis, pronator quadratus, and supinator longus are attached. The third, also obtuse, is indistinct to the second third of the bone.
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whence it proceeds to the middle tubercle of the carpal extremity.

The anterior surface, which is hollow above, presents the medullary hole and the attachment of the flexor longus pollicis below that of the pronator quadratus. The posterior, hollowed in the middle, corresponds to the supinator brevis, the extensors, and abductor pollicis, which are attached to it; and the common extensors, extensor proprius indicis, and extensor pollicis, by which it is simply covered. The external surface, which is rounded, is covered above by the supinator brevis, in the middle by the pronator teres, which are attached to it; and below by the radial extensors (radiales externi), which merely glide over it.

The ulna and radius consist of cancellated structure in the epiphyses, and compact inclosing cancelli in the diaphyses, and are each ossified in three points.

These two bones are mutually connected by a broad web of periosteum continued from that of the bones, and named the interosseous ligament, the principal use of which is to enable the radius to roll laterally in the motions of pronation and supination on the ulna, and to give attachment to muscles without adding to the weight of the fore-arm by intermediate bone.

The bones of the hand consist of those of the carpus, the metacarpus, and the phalanges.

The carpus consists of eight short and irregular-shaped bones, arranged in two rows. Those of the first are the scaphoid or navicular (os scaphoides, os naviculare), the semilunar (os lunatum), the cuneiform or trilateral (os triquetrum), and the pisiform or lenticular (os orbiculare, os pisiforme). Those of the second row are the trapezal (trapezium), the trapezoidal (os trapezoides), the large bone (os magnum, os capitatum), and the unciform bone (os unciforme, os hamatum).

Of these bones, which it would be tedious to describe minutely, it is enough to say, that their names are intended to indicate their shape; that they are connected mutually by cartilaginous surfaces, so as to allow the gliding motion only; and that, besides periosteum, they are invested by ligaments which maintain them in their position, and tend to strengthen and consolidate the wrist, as the basis of support for the hand and fingers.

By the upper articular surface of the scaphoid and semilunar bones, the carpus is connected to the lower extremity of the radius ; while the upper surface of the trilateral bone is contiguous to the fibro-cartilage of the radio-carpal articulation, and the upper surface of which •is in contact with the lower articular surface of the ulna. The pisiform bone, which is attached to the anterior surface of the latter, and thus projects before the plane of the other bones into the hand, may be regarded as a sesamoid bone, which serves as a point of insertion to the tendons of the flexor carpi ulnaris above, the fibres of the adductor of the little finger below, and those of the anterior carpal ligament before.

The inferior surface of the navicular bone is articulated at once to the superior surfaces of the trapezium and trapezoides. The palmar or anterior surface of the former presents a small groove, in which moves the tendon of the flexor carpi radialis, bounded on the outside by the pyramidal process, to which the annular ligament is attached. The os magnum, which is articulated above with the semilunar bone, on the radial side with the scaphoid and trapezoidal, below with two metacarpal bones, and on the ulnar side with the unciform bone, is thus wedged firmly like a central base between the others, and contributes much to the solidity of the carpal articulations. The unciform, which is placed at the inside of the range, and is articulated above with the lunar and cuneiform, laterally with the scaphoid, and below with the two inner metacarpal bones, is distinguished by the unciform process rising from its palmar surface, to which part of the abductor and flexor brevis minimi digiti and the annular ligament are attached, and which, stretched between this and the pyramidal process of the trapezium, form a species of arch over the flexor tendons.

The carpal bones consist of cancellated tissue, invested by a thin pellicle of compact bone. In the foetus and infant they are composed chiefly of brown-coloured, callous substance, homogeneous, but without the smallest trace of bone. Their penetration with this substance takes place about eighteen months or two years after birth.

The metacarpus is usually said to consist of five bones. This is correct so far as situation goes; but one of these bears little resemblance either in shape, connection, or purpose with the other four. It appears, therefore, more natural to restrict the name of metacarpal to the four bones which support the digital phalanges, than to extend it to the thumb, the first bone of which is to be regarded as a phalanx only.

The four metacarpal bones agree in having trapezoidal heads, cylindrical bodies with an elevated longitudinal line before, and rounded convex lower ends for moving on the concave articular surfaces of the phalanges.

Besides the upper trapezoidal surfaces for articulating with the trapezoidal, large, and unciform bones, the lateral margins are provided with facettes, the first and fourth on one side only, the mutual, the second and third, on both, for articulation with each other. In this manner the metacarpal bone of the index finger is articulated above to the trapezoidal and large bone, and on the inside to the metacarpal bone of the middle finger; the latter is articulated above to the large bone, and on the one side to the index metacarpal bone, on the other to that of the ring finger; while the latter and the metacarpal bone of the little finger are articulated above to the unciform bone and to each other.

The bodies of the metacarpal bones are slightly ĩncur-vated before, and form a hollow which corresponds with the palm. In their intervals are contained the interossei muscles, the internal at the volar, the external at the dorsal surface. The anterior surface is covered by the flexor tendons, the lumbricales, and the palmar fascia. The dorsal surface, which is convex in general, is covered by the extensor tendons.

The index metacarpal bone has attached to its radial margin the first dorsal interosseus, to its ulnar, before, the first palmar interosseus, and behind the second dorsal interosseus; while to its upper anterior extremity the radialis internus is inserted, and to the same extremity behind the extensor radialis longior.

To the second or middle metacarpal bone, besides the palmar fascia and the second and third interossei, the adductor pollicis and flexor brevis are attached to the palmar surface; and the extensor radialis brevior is inserted into its dorsal surface.

The fourth or small metacarpal bone, besides the palmar fascia and the third palmar and fourth dorsal interosseus, gives insertion by its dorsal surface to the extensor carpi ulnaris. .

The phalanges or bones of the fingers are fifteen small longitudinal bones placed vertically on each other, three to each finger; or forming ranges distinguished into metacarpal, middle, and unguinal, the first row being the longest, the second shorter, and the third or unguinal the shortest.
[7:2:789]

The metacarpal phalanges agree in having the upper extremities shaped like rounded cubes, with concave cartilaginous surfaces for receiving the lower extremities of the metacarpal bones, and tubercular sides for the attachment of the lateral ligaments. The upper ends of the middle and unguinal are moulded into two cartilaginous cavities with an intermediate ridge, with lateral tubercles for the lateral ligaments. The lower extremities of the metacarpal and middle phalanges, which are smaller than the upper, are rounded and separated by a small groove into two condyles, which are received into the cavities of the upper ends. The lower extremities of the unguinal phalanges, which terminate the fingers, are flattened antero-posteriorly, and moulded into crescentic tips (lunulae) transversely.

The bodies of the metacarpal and middle phalanges are convex behind, and have a surface flat before, bounded on each side by a sharp marginal line, and taper gradually from above downwards. Those of the unguinal phalanges, excepting that of the thumb, are convex before as well as behind. The palmar surface of the metacarpal phalanges is covered by the flexor tendons, which in the superficial muscle are inserted into the anterior and upper part of the middle phalanx, while those of the deep-seated flexor are inserted into the upper anterior part of the unguinal phalanx. The first phalanx of the thumb, which is generally considered as a metacarpal bone, has the abductor magnus inserted into its upper extremity, and the opponens and flexor brevis into its body. The dorsal surfaces are covered by the extensor tendons, which, with those of the lumbricales and interossei, are inserted into the middle phalanges.

The metacarpal and phalangeal bones are compact, with cancellated extremities, and are ossified in three points.

The bones now enumerated are connected so as to admit of motion to various extents. The humerus, articulated with the glenoid cavity of the scapula by a capsular ligament, while the long head of the biceps serves the purpose of a round ligament, admits of motion in every direction,—flexion, extension, abduction, adduction, circumduction, and rotation. The humero-cubital articulation, which is secured by two lateral ligaments, admits of extension and flexion only; but in any position of the ulna in relation to the humerus, the radius rolls on the former, so as to produce those motions of the wrist and hand which are denominated pronation or internal rotation, and supination or external rotation.

The carpal bones are articulated chiefly with the radius, so as to admit of flexion and extension, adduction and abduction, and even some degree of circumduction and rotation. The metacarpal bones are limited in motion. The metacarpal phalanges admit of flexion and extension, abduction and adduction, circumduction and rotation; while those of the middle and unguinal range are confined to flexion and extension. The precision, nevertheless, of which these motions are susceptible, with the numerous modifications which they undergo in combination with the opposable powers of the thumb, and the nicety and delicacy of tact inherent in the skin of the fingers, arc the means from which the human hand derives its remarkable aptitude for all the mechanical arts, and all operations requiring manual dexterity. By the combination almost endless of a number of simple motions, so many complex motions arc produced, that it is difficult to set limits to the degree of perfection which the hand and fingers, as an organ of prehension, may attain.

§ 7. The Bones of the Pelvic Extremities.

The bones proper to the lower or pelvic extremities are, the thigh-bone (femur), the shin-bone (tibia), and leg-bone (fibula)·, with the knee-pan (rotula, patella), seven tarsal bones, four metatarsal bones, and 15 phalanges.

The thigh-bone (femur, os femoris) is the largest, thickest, strongest, and heaviest bone of the skeleton.

The upper or iliac extremity consists of a head, neck, and two tuberosities named troehaniers. The head is globular, incrusted by cartilage and synovial membrane, unless at its internal point, where there is an irregular depression for the iųsertion of the round ligament, and is lodged in the cotyloid cavity (acetabulum). It is situate internally in relation to the shaft; and its axis, which forms with that of the latter an obtuse angle, variable in extent according to age and sex, is represented by that of the neck, a contracted cylinder of bone, varying in length according to the same circumstances, flattened before and behind, presenting numerous vascular holes, and covered by fibrous slips and synovial membrane. The junction of the neck with the bone is marked by a large prominent body named the trochanter major (τ), in which four surfaces may be recognised; an external lateral, for the insertion of the glutaeus medius, and the motion of the tendon of the glutaeus maximus ; an internal with a pit, for the insertion of the tendon of the pyriformis, of the gemelli, and of the obturators; an anterior for the insertion of the tendon of the glutaeus minimus ; and a posterior for that of the quadratus femoris. At the union of the neck with the diaphysis below, and externally, is a conical eminence named the small trochanter (t), to which the united tendon of the psoas magnus and iliacus internus is fixed. The spaces between the trochanters before and behind are united by oblique rough lines, to which the femoral margin of the capsular ligament is attached, and the entire space within which is continuous with the articular cavity.

The lower or tibial extremity, which is large, is moulded into two rounded eminences named condyles ∕%ovδυλo∕) (1, 2; a, b); the one internal, deeper, and larger than the external, separated by an antero-posterior depression (fossa intercondylaris), and prominent and convex behind. Each condyle has an external and internal surface, while the articular one, which is incrusted by cartilage and synovial membrane, is shaped something like a horse-shoe, incurvated upwards in the middle before, and behind on each side, with elevated irregular margins for the attachment of the articular capsule. The intercondylar depression before receives the upper part of the knee-pan (patella), while in the intercondylar cavity behind are lodged the fimbriated margins of the synovial membrane, with the femoral ends of the cross ligaments, the anterior of which is inserted into the inner surface of the external condyle, and the posterior into that of the internal condyle. The outer or fibular surface of the external condyle presents an eminence for the attachment of the external lateral ligament, and a depression below for that of the pcplitaeus. The outer or tibial surface of the internal condyle has a prominent tubercle, to which are fixed the internal lateral ligament and the tendon of the adductor magnus. In a pit above each condyle the heads of the gemellus (gastrocnemius externus) are fixed.

The shaft or body, which approaches the cylindrical shape, is incurvated, with the convexity before, and the concavity behind (F, f). The anterior surface is uniformly round, and covered by the cruraeus, which is fixed above to the interval between the trochanters. The posterior surface presents a rough elevated line, descending from the base of the large trochanter, meeting a similar line descending from the small trochanter, and inclosing a triangular rough space, forming about the middle third of the bone a rough elevated line (linea aspera) (1), which again is parted into two, less distinct; one terminating[7:2:790] on the external, the other very faint on the internal condyle. To the upper part of the external line, where it is most prominent, the tendon of the glutaeus maximus is inserted; next is the short head of the biceps ; and to the rest are fixed the fibres of the vastus externus. To the inner line the pectinaeus and adductor brevis are inserted above, and the vastus internus is attached below; while the adductor longus and ηιagnus are fixed to its whole length, unless at one point, where it is interrupted about three inches above the condyle by a smooth surface, on which the femoral artery passes under the tendon of the ajdductor magnus, to continue its course between the condyles, where it becomes the popliteal artery.

The femur, which is one of the most perfect examples of a long cylindrical bone, is compact in the diaphysis, with distinct medullary canal, and cancellated in the epiphyses. It is ossified in four portions; one for the diaphysis and neck, one for the two condyles, one for the head, and in general one for the trochanter major. The neck, which is short in early life, becomes long in adult age, and the body acquires its peculiar incurvation apparently from muscular action. In the female this incurvation is greater than in the male, and the neck forms a greater angle with the body.

The knee-pan (rotula, patella) (p) is a short bone, shaped like a heart, with the apex downward, convex and fibrous before, where it is covered by tendinous matter; flat above, where the rectus, the two vasti, and the cruraeus, are inserted; plane and concave behind, where it is covered by cartilage and synovial membrane, and separated into two unequal divisions by a middle ridge, forming the anterior wall of the knee-joint, and applied by its superior half over the anterior intercondylar fossa. The lower apex is rough for the attachment of the inferior ligament; and to the margins are fixed those of the fibro-tendinous capsular, by which it is connected to the femur and tibia.

The knee-pan, which has a peculiar cancellated structure, invested by a thin plate of compact bone, is to be regarded partly as a sesamoid bone for the insertion of the common tendon of the four extensors of the leg, partly as an appendage or epiphysis to the superior part of the tibia, performing to that bone the same function which the olecranon does to the ulna.

The tibia is a prismatic-shaped long bone, situate at the inner and anterior region of the leg, with the femoral condyles above, the astragalus below, and the fibula on the external side.

The head, upper or femoral end, is large., and of an irregular oval shape. It presents two slightly concave elliptical cartilaginous surfaces, with the long diameter antero-posterior, separated by a rough vascular space, large before and narrow behind. Of these elliptical surfaces the external margin is most regular, and presents a crescentic or lunated mark for the attachment of the semilunar fibro-cartilages, which thus increase the concavity of the articular surfaces for the reception of the condyles. The inner or mesial margin of each is elevated into a curved peak, mutually separated by a depression. These eminences, which are jointly named the spine of the tibia, correspond in flexion and extension to the intercondylar fossa. Before is a triarcual surface, rough for the insertion of the anterior crucial ligament, and behind a notch for that of the posterior. The lateral circumference of the head, which is rough, and marked by vascular holes, presents before a triangular surface, the upper half of which corresponds to the inner surface of the knee-pan, and is contained within the cavity of the joint; while the lower angular portion is convex for the insertion of the inferior patellar ligament, or the last insertion of the tendon of the rectus and vastus externus. The sides, which are rounded and prominent, are named respectively the external and internal tuberosities, and give attachment to the external and internal lateral ligaments. To the back part of the internal also the tendon of the semimembranosus is fixed (d), while that of the external presents a cartilaginous facette for the articulation of the head of the fibula (c).

The lower or tarsal extremity, which is much smaller, is nearly quadrilateral, with a cartilaginous surface concave transversely, with elevated anterior and posterior borders, and the internal raised into a vertical eminence named the inner ankle (malleolus internus) (f), to the apex of which the internal lateral ligament is fixed. This cartilaginous surface, which receives the head of the astragalus, is surrounded by a furrow, very distinct before, in which ligamentous fibres are inserted; while the external margin, which is broader than the internal, presents between two prominences a trilateral hollow, in which the tarsal end of the fibula is lodged. The anterior surface is covered by the tendons of the tibialis anticus and extensor proprius hallucis ; and the posterior, behind the internal ankle, is marked by a groove for the tibialis posticus and flexor longus digitorum, and another for dne flexor longus hallucis.

The body or diaphysis, which is thick above, is prismatic, and presents three surfaces, bounded by the same number of lines. The first, which is anterior (crista), descends sharp and prominent from the anterior margin of the external tuberosity to the fore part of the internal ankle, and, though subcutaneous, gives attachment to the tibial aponeurosis and the tibialis anticus. To the external, which is sharp, and descends from the posterior margin of the same tuberosity to the anterior tubercle of the lower end, the interosseous ligament is fixed. To the internal, which is obtuse, and rather rounded, and descends from the posterior part of the internal tuberosity to that of the inner ankle, the poplitaeus above, and the second or inner head of the solaeus, with the flexor longus digitorum, are attached.

The surfaces bounded by these lines are interned, external, and posterior. The first, which is convex, gives insertion above to the sartorius, gracilis, and semitendinosus, and is elsewhere covered by integuments only. The external is concave above, where the tibialis αnticus is fixed; convex below, where it is covered by the tendons of this muscle, and of the extensor communis and proprius. The posterior is crossed by an oblique line (T, 1, Plate XXV.) descending from the fibular articular surface to the internal line, and forming two spaces, the superior of which, triangular, is covered by the poplitaeus inserted into the oblique line, while the lower, occupied by the tibialis posticus and flexor longus, presents also the medullary holes.

The tibia, compact in the diaphysis, with medullary canal, cancellated in the epiphyses, is ossified in three portions, one for the former part, and one for each of the latter.

The fibula, which is the most slender bone of the skeleton of equal length, is situate at the outer side of the tibia, with its lower extremity anterior to the plane of the upper, articulated above with the latter bone only, below with the tibia and astragalus at once.

The head or tibial end, which is of an irregular cuboidal shape, presents above an oblique, trilateral, cartilaginous surface, articulated with that behind the external tibial tuberosity, by which also it is overhung. Before is a triangular surface, slightly convex, for part of the femoro-tibial ligament; behind, a tubercular surface for ligamentous insertions; and externally, between the two, is an extensive pentagonal surface for the insertion of the [7:2:791]bicipital tendon, terminating above in an angular point, to which is fixed the peroneo-tibiał ligament.

The lower or tarsal end consists of a pointed trilateral pyramid, the external surface of which, somewhat convex, is subcutaneous, and forms the external or fibular ankle (malleolus externus) (e). Within is a trapezoidal cartilaginous surface, which is articulated with the astragalus; and behind and below is a rough triangular surface, with a cavity for the insertion of the fibulo-tarsal ligament, while the external ligament is fixed to its angular tip. The posterior surface presents a groove, sometimes two, incrusted by fibro-cartilage for the motion of the peronaei longus et brevis.

The body is marked by several lines inclosing surfaces rather irregular in shape and extent. Among the former the following may be recognised4—An anterior, commencing about 2∣ inches below the head, distinct in the middle, where the aponeurosis common to the extensor longus digitorum and peronoeus tertius before, and the peronoeus longus et brevis behind, is attached, and bifurcating about 2∣ inches above the lower end into an anterior and posterior, terminating on the anterior and posterior margins respectively of the malleolus externus, inclosing a triangular space, which is covered by integuments only. The internal, descending from about an inch below the head to the anterior edge of the internal malleolus, coincides there with the anterior part of the anterior line. To this, above and in the middle, the tibialis posticus and flexor proprius pollicis, and below the interosseous ligament, are attached. The external or posterior descends from the posterior part of the head, obtuse, and winds round below to the posterior part of the tarsal end, giving attachment to an aponeurosis intermediate between the lateral peronaei without, and the flexor proprius and solaeus behind. Between the external and the anterior is an oblique line, to which the interosseous ligament is fixed.

The external surface between the anterior and posterior lines, narrow above, convex and broad in the middle, and winding spirally round the axis of the bone, is covered by the peronoeus longus and brevis. An anterior, plane, is covered by the extensor longus and peronoeus tertius. The internal or tibial is divided by the oblique line into two; an anterior for the extensor proprius, and a posterior for the tibialis posticus. To the posterior surface above, which is convex, the solaeus is attached; and in the middle and below the flexor longus pollicis ; while, by the rough triangular surface below, the bone is articulated with the trilateral cavity of the tibia.

The fibula, which is ossified in three portions, partakes of the general characters of structure common to the long bones.

The tarsus consists of seven short irregular-shaped bones, the astragalus, the heel-bone (calcaneum, os calcis), the scaphoid, cuboid, and three cuneiform bones.

The first (talus, astragalus) has a convex cartilaginous surface above for articulation with the lower end of the tibia, continuous with a similar trilateral concave surface on the inside for articulating with the malleolar process, and with a smaller triarcual surface on the outside for the fibula; two cartilaginous surfaces, separated by a deep pit below, for articulating with the calcaneum; and an anterior eminence, with a convex cartilaginous surface, for articulating with the scaphoid bone before. The calcaneum, which is the largest, consists of the posterior tuberosity (talus) (c), for the insertion of the united tendons of the gastrocnemius and solaeus, and that of the plantaris ; two upper cartilaginous surfaces, separated by a ligamentous pit, for articulating with the astragalus ; an anterior cartilaginous trilateral surface for the cuboid bone; an internal lateral sinuosity for the passage of the flexor tendons, that of the tibialis posticus, and the posterior tibial artery and nerves; and, lastly, an external lateral surface, covered by integuments and the tendons of the lateral peronaei.

The scaphoid bone is connected by its posterior concave surface with the anterior convex one of the astragalus, and presents before a cartilaginous surface with three facettes for the three cuneiform bones, and on the outside a small facette for the cuboid. On the inside is a prominent tuberosity for the attachment of the tibialis posticus. The cuboid bone, which constitutes the outer margin of the tarsus, and is articulated with the trilateral surface of the calcaneum, and by a minute facette with the scaphoid bone, is chiefly distinguished by an oblique or diagonal groove, for the tendon of the peronoeus longus. The third and fourth metatarsal bones are articulated to its anterior surface.

The three cuneiform bones agree in having posterior cartilaginous surfaces for articulation with the scaphoid bone, and anterior ones for that with the first phalanx of the great toe, and the metatarsal bones of the second and third toes. The internal surface of the large cuneiform bone is convex, covered by integuments; the external or fibular cartilaginous, with two facettes for articulation with the second cuboid bone and the first metatarsal. Its lower surface is irregular for the insertion of the tibialis anticus, and part of the tibialis posticus. The second cuneiform bone, which is the smallest of the three, and the most like its name, is wedged between the scaphoid behind, the first and third on each side, and supports the first metatarsal bone before. The third, which also is not unlike its denomination, is wedged between the scaphoid behind, and the second cuneiform and the cuboid bone, and sustains the second metatarsal bone; while the third and fourth are articulated with the anterior surface of the cuboid.

Of the metatarsal bones there are four; the first three similar to each other; the fourth, which sustains the phalanges of the small toe, distinguished by a large oblique angular head for the insertion of the tendon of the peronoeus brevis, while that of the peronoeus tertius is fixed above. Of the other three the heads are trilateral or wedge-shaped with the base upwards, with cartilaginous facettes on the sides for mutual articulation. The bodies are cylindrical, and, tapering, terminate in round heads flattened laterally. The dorsal or upper surface is covered by the extensor tendons, the extensor brevis digitorum, and the dorsal vessels and nerves derived from the anterior tibial artery and nerve. The surface of these bones is so constructed that it forms an arched or convex inclined plane, descending from the tibial to the fibular side of the foot. In the anterior or plantar surface, which is concave, arc lodged the abductor hallucis, abductor minimi digiti, flexor brevis, the flexor tendons, the accessory flexor, the lumbricales pedis, flexor brevis hallucis, abductor hallueis, flexor brevis minimi digiti, transversalis, and the external and internal ranges of the interossei.

The phalanges of the toes, in number 15, bear a general resemblance to those of the fingers; but are considerably shorter, unless in the instance of the great toe. Like these also, they are disposed in three ranges,—metatarsal, middle, and unguinal.

The bones now described are united so as to admit of different degrees and forms of motion. The head of the femur, lodged in the acetabulum, is retained in that cavity not only by the capsular and round ligaments, but by the numerous strong muscles with which the hip-joint is surrounded. The length of the neck, which is peculiar to the human subject, throws the supporting column of [7:2:792]the bone to a greater distance, not only from the pelvis, but from the mesial plane and centre of gravity; and this character, with the great proportional length of the bone, and the extent and direction of the pelvis, constitutes the most decisive argument in favour of the doctrine, that man must support himself in the erect position on the two pelvic extremities. In most quadrupeds the neck of the femur is short; the cylinder is shorter than the tibia, and not arched; and the pelvis, both by its vertical direction and peculiar dimensions, is calculated for the quadruped motion only. The femur admits of motion in every direction,—flexion, extension, adduction, abduction, circumduction, and rotation.

The tibia, with its appendage the knee-pan, is articulated to the condyles of the femur by means of an external and internal lateral ligament, strengthened by an anterior or patellar ligament, posterior fibres, and an anterior and posterior cross ligament, contained within the synovial membrane. The effect of this arrangement, with the anatomical configuration of the articular ends, is to allow cardinal opposition, or flexion and extension only. A small degree of rotation, nevertheless, may be effected.

The fibula is articulated to the tibia above by a genuine capsular joint, and below by fibrous matter, and connected at its internal side by a duplicature of periosteum forming the interosseous ligament. These connections admit of little motion, and the chief use of the fibula is to give attachment to several muscles which bend or evert the foot. The chief weight of the person, divided as it is between each lower extremity, is communicated from .the pelvis to the femur, thence to the tibia, and finally to the astragalus and calcaneum behind, and the metatarsal bones before. The motion of opposition is confined to the former, which rolls backwards and forwards in the cavity formed by the lower extremity of the tibia and the fibula in the flexion and extension of the foot. In this, therefore, which forms the ankle-joint, all the motions of the foot as a whole are executed. It appears further to be susceptible of a slight degree of lateral rotation, so as to contribute to the eversion and inversion of the foot.

The tarsal bones are mutually connected by cartilaginous surfaces, and secured by numerous fibrous bands, so as to admit of the gliding motion only. This motion is further between each individual articulation very limited, and its general amount is inconsiderable. The great use of the tarsal articulations is evidently stability and solidity as a base of support, not mobility.

The bones of the foot form two distinct and separate arches,—an antero-posterior and a transverse. The first is constituted by the posterior part of the heel-bone behind and the metatarso-phalangeal articulations before; and its chief use is to distribute the weight of the extremity from the astragalus, which may be regarded as the centre, to the os calcis and extremities of the metatarsal bones on each side. In standing, for example, either on one foot or both, the weight of each extremity is distributed before to the metatarso-phalangeal joints, and behind to the tuberosity of the os calcis, while the anterior part of the latter bone and the whole second range of tarsal bones do not touch the ground. The second arch results first from the arrangement of the cuneiform bones with the scaphoid, and that of the cuboid with the os calcis ; and next from the arrangement of the metatarsal bones. These arches, which are indistinct in early life, become conspicuous as the bones are completed, and acquire their complete developement in adult age. These arches are of great use in the alternate elevation of each half of the person in progression, in ascending an inclined plane or a series of steps, and especially in springing and leaping.

The phalanges are articulated with the metatarsal bones and with each other, so as to admit of flexion and extension chiefly, with a very limited extent of abduction and' adduction. The articulation of the great toe, also destitute of the power of opposition, abridges much its extent of motion. While these circumstances, with the great brevity of the phalanges, render the foot much less perfect than the hand as an organ of prehension, they extend its sphere of support, and enlarge its powers as a locomotive agent.

The pelvic and thoracic extremities present several points of resemblance which have been well traced by Soemmering. The head, neck, and tuberosities of the humerus resemble the head, neck, and trochanters of the femur ; and if the lower end of the former bone is articulated both with the ulna and radius, while that of the latter is connected to the tibia only, there is still sufficient analogy between the lower ends of both bones. The tibia resembles the ulna above, with the knee-pan corresponding to the olecranon; but the lower extremity of the tibia is represented by that of the radius, in consequence of the extensive connection of the latter bone with the carpus for the purpose of pronation and supination. The navicular and lunar bones of the carpus are represented by the single astragalus, — an arrangement which appears to be allied in the latter case to the purpose of stability and solidity. The calcaneum may be regarded as an enlarged os magnum, fitted for the same purpose; and even in the shape and position of the scaphoid bone the same object may be recognised. This comparison, however, it is superfluous to pursue farther. The general conclusion is, that the thoracic extremities are intended to combine with strength great extent and precision of motion, while the purpose of the pelvic is stability, solidity, and strength.

SECT. II. — MYOLOGY; THE ANATOMY OF THE MUSCLES.

The muscles, with their appendages the fasciae, tendons, and synovial sheaths, constitute the second division of the locomotive organs. By the term muscle, indeed, in Special Anatomy, is meant not only a mass of flesh adequate to effect motion, but an organ consisting of fascia, muscular flesh, and tendon, connected by the first and last substances to the parts, fixed or movable, to be approximated. While the middle portion is denominated belly (venter), the two extremities are most properly named attachments; though by others they have been termed respectively head or origin (caput, origo), and insertion (insitio) or termination (finis), according as the one or the other end has been imagined to be most fixed.

By the contraction of the middle portion or belly the two extremities are approximated; and according as the one is connected with a bone or soft part more movable than the other, that movable portion is approximated to the fixed. This, which is the general effect of muscular action, is well exemplified in the primary bones of the extremities, the muscles of which have their fixed end in general in the trunk, and their movable end attached to the bones of the extremities. Thus in the case of the pectoralis major (p), Plate XXVII., and latissimus dorsi (l, D, Plate XXVIII., the fixed ends are in the trunk, and the movable or insertions are in the humerus; and the effect of the contraction of the belly is to carry the humerus fon-ward over the chest in the one case, and backward on the trunk in the other. This is easily applied to other muscles, as to those of the face.

The converse of this arrangement nevertheless may take place. The extremity, which in ordinary circumstances is the most movable, may be converted into the [7:2:793]fixed; while that which is fixed becomes movable. Thus, in the case of the two muscles already mentioned, the humerus may become the fixed point; and the effect will be to elevate and approximate the trunk to the part to which the extremity is fixed.

Though all the muscles are agents of motion, all are not of locomotion; and it is chiefly the muscles connected by both ends with the skeleton, and especially those of the extremities, which are entitled to this distinction. The muscles of the face are connected always by one end, often by both, with the skin, and hence are cutaneous muscles. Those of the lower jaw and pharynx are organs of motion simply to move the parts with which they are connected in the acts of mastication and deglutition. Those of the larynx are of two orders, the common or extrinsic, connected to some of the bones of the head and chest; and the proper or intrinsic, pertaining to the laryngeal cartilages only. Those of the eye and ear, external and internal, are equally unconnected with the locomotive faculty.

These circumstances have induced several authors, especially the ancient anatomists, and among the moderns Winslow, to arrange the muscles according to the parts which they move. By others, however, especially Douglas and Albinus, they have been classified according to the regions which they occupy; and this method, which is certainly more strictly anatomical, has been more or less adopted by Innes, Sabatier, Bichat, and Boyer. To the first method the principal objection is, that the same muscle may pertain to different classes of organs, and may effect different purposes in each; while of the second it must be admitted, that it communicates no information regarding the remarkable part which the muscles perform in the complicated processes of the animal machine. This consideration it was which induced Albinus, after a minute description of the situation, connections, and separate actions of each muscle of the human body, to construct a table representing the various classes into which they may be divided, according to the parts on which they act; for the same reason, doubtless, Soemmering arranged them according to the organs to which they belong; and for the same reason Portal, after a description equally minute with that of Albinus, gives a second account of the muscles as they are observed to act in the living body.

In the following tabular view, modified from that given by Albinus in the fourth book of his Historia Musculorum, the muscles are arranged according to their regions.
[table]
[table]
[7:2:794]
[table]
[table]

The limits assigned to the present treatise preclude particular details on the situation and relations of this numerous list of muscular organs. Any description sufficiently minute for the purpose of explaining the situation, attachments, relations, and actions of the muscles of the different regions, would be tedious in the extreme, and would not be intelligible without dissection; and no description according to their actions only would be intelligible, without a previous account of their anatomical relations. For these reasons it seems most expedient to direct the attention of the reader to a few general circumstances only. For descriptive details the reader will study with advantage the third book of the elaborate and accurate Historia Musculorum of Albinus, or the more recent treatise of Sandifort. The descriptions of Innes are clear, short, and sufficiently minute; and a good account of the muscles, as they appear on exposition, is given in the London Dissector. Of systematic treatises, the second volumes of those of Soemmering, Portal, and Bichat are the best.

This section, therefore, we shall conclude with such a general view of the muscles as agents in the attitudes and motions of the trunk and extremities, as, with the occasional remarks on their situation and connections in describing the bones, may be easily intelligible. It is further proper to advert briefly to those of the flexor muscles of the fingers, partly with the view of illustrating the general effects of muscular action, partly to show the mechanism by which the hand and fingers are enabled to execute such a variety of nice and delicate motions.

The muscles of the trunk are employed not only as agents of motion and sustentation, but as the protecting walls of the large cavities. Thus the external and internal ranges of intercostals, the two pectorals, and the serratus magnus, operate not only in moving the ribs and shoulder respectively, but in contributing to complete the walls of the thorax, and to protect the internal organs. The diaphragm is not only an agent in enlarging the chest downwards, but constitutes an essential partition between the thoracic and abdominal viscera, prevents the lungs and heart from descending into the abdomen, and the stomach and bowels from being thrust upwards into the chest. These characters are still more conspicuously displayed in the recti abdominis, obliqui externi et interni i and trans- [7:2:795] versi abdominis, which operate a little in drawing the chest downwards and compressing it before and on the sides, but act much more powerfully as retaining and supporting walls of the abdominal viscera, counteracting by the inward and upward action the downward impulse of the diaphragm. In this manner the abdominal viscera, placed between two opposing but equally balanced powers, are retained in the cavity, and prevented from being protruded upwards or downwards, while they are subjected to the alternate motions of inspiration and expiration.

The muscles of the trunk are employed in retaining that part of the skeleton in the erect attitude, in balancing it properly on the pelvic extremities, in occasionally inflecting and extending it, in bending it to one side, or in producing rotation. Those of the spine and back are particularly the agents of the erect attitude, and of extension; and those of the anterior region are employed in inflecting the person.

The muscles of the superior extremities taken together are the agents of numerous varied motions. Though the principal object of the thoracic extremities is prehension, or embracing any object or objects firmly either by one or both hands, this may be modified in various ways, so as to give rise to prepulsion, traction, and constriction; while diduction and circumduction are the result of the combinations of the simple movements,—abduction, adduction, flexion, and extension.

Prepulsion may be either instantaneous or continued. The first takes place in the act of inflicting a blow or repelling an object. All the flexors are previously put in action to shorten the member, which is then at once forcibly extended, and communicates a violent shock to the part of the object to which its extremity is applied. Of this motion, in which the extension takes place in the scapulo-humeral and humero-cubital articulations, the deltoid and brachialis externus, or third head of the triceps, are the chief agents. The wrist and fingers arc almost passive. But an analogous motion is executed by the latter in giving a fillip. In continuous prepulsion, for instance, or the act of impelling an object, the mechanism is of two kinds. In the first case, the member being previously extended and supported on the object, the individual inclines the trunk, and avails himself of its weight; while the member, remaining passive, becomes a lever moved by gravity. In the second case, the continued action of the extensors retaining the member forcibly extended, impels the object without interruption. When, for example, a man pushes a wheelcarriage before him, the superior extremities are extended and communicate motion to the carriage, while the trunk approaching it immediately, the extremities are again inflected; and so forth successively. In most instances this twofold mechanism is combined. When in prepulsion the body impelled is fixed, the impulse is thrown back on the person of the prepelling agent. Examples of this effect of prepulsion are observed in the act of rising from a seat by the occasional use of the thoracic extremities, and in pushing a vessel from the shore by means of an oar .or pole.

Traction, which consists in a general action of the flexors of the thoracic extremities, is directly the reverse of prepulsion. Its effect is to diminish the space between the agent and the object drawn, which takes place by shortening the member; while in prepulsion this space is enlarged by elongating or extending the member. In the case of a very great effort, for instance that of detaching a piece of wood strongly fixed in a wall, the action of the flexors is aided by the weight of the trunk, which is instinctively inclined in the opposite direction; and if the body drawn yields at once, a fall is often the result, because in this inclination the centre of gravity is subverted. In another form of traction, in which the body grasped does not yield, and when the action takes place upwards, the effect is to elevate the person of the agent by the flexors of the superior, and even occasionally of the inferior extremities. Familiar examples of this are afforded in the act of climbing walls, trees, and occasionally rocks, in ascending the rigging of a ship, and still more forcibly in the manner in which the active seaman ascends a single rope.

Constriction consists in the forcible and continued inflection either of a single hand or of the whole of both members. In the first case the agents are the superficial and deep flexors, and the flexors of the thumb and little finger; and in the second, with the action of these muscles, that of the biceps, brachialis internus, and coraco-brachialis is combined. This motion can neither be so sudden as that of prepulsion, nor, like it, can it be aided by the weight of the person.

Diduction, which consists in the forcible separation of the upper extremities from each other, as in swimming, is effected partly by the latissimus dorsi and teres major, partly by the posterior fasciculi of the deltoid moving the whole extremity in the scapulo-humeral articulation.

Circumduction, which also is exclusively confined to the scapulo-humeral articulation, is effected principally by the deltoid, large pectoral, latissimus dorsi, teres major, &c.; while rotation is performed by the supraspinatus, infraspinatus, teres minor, subscapularis, &c.

Besides these general classes of motion executed by the thoracic extremities, to them also belongs the power of assuming many of those attitudes and all the varieties of gesture which man employs for the purpose either of expressing his feelings or giving significance and animation to the language which he adopts for that purpose. How much these gestures, when well chosen and properly introduced, aid both the expression of the countenance and the language of the lips, is well known to the public speaker and the dramatic performer.

Besides the ordinary flexors of the wrist (radialis externus et internus, ulnaris internus), there are two common flexors of the fingers, one superficial (sublimis), the other deep-seated (profundus) ; the thumb has a long and short flexor, and the little finger has a short flexor. The flexor muscles, therefore, may be distinguished into four orders; those common to the wrist and hand, those common to the hand and fingers, those proper to the fingers, and those proper only to some of the fingers. Though the radialis internus and ulnaris internus chiefly bend the wrist and hand, yet both the superficial and deep flexors, by passing beneath the annular ligament, co-operate in the same motion, and necessarily bend the hand previous to their final action on the digital phalanges. In this they are considerably aided by the action of the palmaris longus and the palmaris brevis, which render the palmar aponeurosis tense, and enable it to afford the necessary resistance to the subjacent flexor tendons.

The superficial flexor., the tendons of which are inserted into the anterior and citerior part of the second row of phalanges, has the effect of bending that part of the fingers; and further, by being bound down by a ligamentous sheath to the first phalanx, inflects them at the same time into the palm. The slits in each tendon allow those of the deep flexor to pass forward on the median line of each phalanx, to be inserted in the unġuinal phalanges, and thereby to operate most directly and perfectly in inflecting them on the palm; and, by being confined also in the same sheath by strong ligamentous bands, aid in inflecting the second and first range of phalanges. (Plate XXVIII. fig. 2 and 3.) [7:2:796] These actions are further facilitated and modified by another class of muscles. The lumbricales, which, situate in ' the palm, are attached above to the tendons of the flexor .profundus, and inserted sometimes into the extensor ten- l dons, sometimes into the lateral regions of the phalanges, may either concur with the profundus in bending the first phalanges, or they may adduct or abduct the fingers, according to the separate or conjunct motion; and hence are of the utmost importance in all nice and minute motions of the fingers. Without the lumbricales, which are peculiar to man, it would be impossible for the human fingers to execute those minute and rapid movements which are necessary in performing on musical instruments; and the great advantage which one individual possesses over another in what is denominated execution, consists chiefly in the perfect use of these little muscles. In playing on the piano-forte especially, the lumbricales are of the most essential service; and though the superficial flexor enables a lady to strike the keys, the former must be employed in the more minute and delicate motions requisite in the transition through numerous chords.

In this action the internodii at the same time appear to be auxiliary; and their connections are calculated to modify the action of the flexors.

Another peculiarity in the human hand consists in the four muscles with which the thumb is provided, and the two connected with the little finger. By means of its short abductor, short flexor, and adductor, the thumb may be separated, inflected, and approximated to the hand quite independently of the fingers, and with the utmost precision. But from the opponens it derives the remarkable property of being accurately and precisely applied to the tip of any one of the fingers, and thus made to grasp minute objects, which could not without this be effected. From this muscle, in short, the human hand derives its power of appliance to all the arts requiring nice manual operation. Without the opponens there is no penmanship, no painting, no drawing, no tracing, no needlework, no engraving; in short, none of those operations requiring the obedience of the hand to the conceptions of the mind and the guidance of the eye.

The movements of the lower extremities are less distinguished for precision and delicacy than those of the superior; and though the foot has both lumbricales and interossez, the brevity of the phalanges compared with the length of the metatarsal bones, and the close connection of the toes, form insurmountable impediments to the rapidity and nicety of motion which is observed in the inflections of the fingers. The circumstance, however, which places the foot at an immeasurable distance behind the hand as an organ of prehension, is the want of the opponens. Void of this, the human foot is little more than the foot of the quadruped, constituting chiefly a base of support, and susceptible of such motions only as are requisite to progression. It is expedient, therefore, to consider shortly the agents by which these functions arc performed.

Station, or that attitude in which man supports himself in the erect position on a horizontal plane, is effected by the foot being planted firmly on the ground by means of the gemellus, solaeus, tibialis anticus, peronaeus longus et brevis, flexor longus communis digitorum pedis, flexor hallucis proprius, flexor hallucis brevis, flexor brevis digiti minimi et digiti medii, the lumbricales, and interossei. At the same time the leg is fixed to the ground by numerous muscles,—before by the extensors of the great toe and toes generally, by the peronaeus tertius, partly by the tibialis anticus ; externally by the peronaei longus et brevis ; within by the tibialis anticus and posticus ; and behind by the gemellus, solaeus, semitendinosus, and long flexors of the toes. The knee is at the same time stretched by the four extensors, aided by the tensor vaginae femoris.

The equilibrium of the trunk and pelvis on the heads of the thigh-bones is maintained by several powerful muscles, connecting the former to the latter. Before, for instance, this action is performed by the sartorius, rectus, the two psoae, and the iliacus internus ; behind by the biceps, semitendinosus, and semimembranosus ; without by the glutaeus and tensor vaginae femoris ; and within by the pectinaeus, the adductors, and the gracilis. By these muscles the pelvis is impelled on the axis of the two femora only, and is prevented from inclining in any other direction. To maintain the trunk above the pelvis in the same steady position, numerous other muscles concur. Behind are the various extensors of the vertebral column and trunk; the longissimus dorsi and sacro-lumbalis on each side, the cervicis descendens, splenius and biventer cervicis ; the transversi cervicis, and spinalis cervicis et dorsi ; the semispinalis, multifidus, and interspinales on each side. Before are the sterno-mastoid, the great and small anterior recti, the longi colli, and anterior scaleni ; and on each side are the trachelo-mastoid, the lateral scaleni, the intertransversi, and the lateral recti. In this enumeration it is manifest that the muscles of the posterior surface of the trunk and spine are at once more numerous and more powerful than those on the anterior,—an arrangement which is rendered necessary to counteract the effect of the weight of the thoracic and abdominal viscera on the anterior side of the vertebral column, which is thus rendered liable to anterior incurvation, and which becomes so in old age, notwithstanding the agents now mentioned.

This circumstance is further illustrated in the number and size of the muscles by which the head is retained in the erect position, and prevented from inclining forwards. These are the cucullares, the splenii capitis, biventres cervicis, and posterior recti on each side—all powerful, and several of them large.

Station on both pelvic extremities, therefore, requires the co-operation of a very considerable number of powerful muscles; and it is a mistake to imagine, as some authors appear to do, that a small degree of muscular energy is requisite for this purpose, and that the skeleton is the chief means of maintaining the erect position. Without the skeleton, as points of support, the muscles cannot act; but without the muscles the bones are passive brute matter.

In station on one extremity only, a different and certainly a less degree of muscular action is requisite. All the external muscles of the fixed member are at first strongly contracted, to prevent it from - gliding inwards, in which direction the trunk, not supported by the opposite limb, tends to impel it. Proceeding from below upwards, we find the lateral peronaei, the vastus externus, and even the rectus, draw the limb outwards; while the tensor vagina, femoris, the glutaeus medius and minor, carry the pelvis, and with it the trunk, in the same lateral direction. In this case the weight of the person is employed in antagonizing the muscles of the side thrown into action; and the person is balanced between these two forces.

Elevation on the tip of the foot is effected chiefly by the action of the muscles, which extend the phalanges on the metatarsal bones, viz. the tibialis anticus, extensor hallucis, extensor longus digitorum, and even the extensor brevis ; all of which must fix the leg before, and the tarsal and metatarsal part of the foot on its phalangeal region, before the latter can be employed to elevate the person. These extensors, therefore, perform in the tip-toe attitude the duty which the gastrocnemius and solaeus execute behind in ordinary station; and the smaller power [7:2:797]of the former readily explains the difficulty of maintaining this attitude for a long time.

Progression or gait (incessus) consists in the anterior propulsion of the person by the alternate propulsion of each pelvic extremity. In this, therefore, not only are the muscles necessary to maintain the erect position put in action, but those which bend the lower extremity on the trunk operate on one side, while the extensors of the other maintain that extremity for the instant fixed. Progression consists of a series of steps (passus) ; and each step consists in the antero-posterior separation of the pelvic extremities by the propulsion of one, while the other remains fixed. Supposing the left foot to be the fixed one, the right foot is elevated, and the leg is propelled by the contraction of the gemellus, solaeus, semitendinosus, tibialis anticus et posticus ; while at the same time the extensors of the knee raise the leg, and the psoas, iliacus, pectinaeus, triceps adductor, sartorius and gracilis, with the tensor vaginae femoris, raise and stretch the whole limb. When this is accomplished, the right foot, with the knee extended, the elevating muscles being relaxed, and the trunk, are inclined forwards, and the foot is planted at some distance before the left.

In this motion, however, in which the trunk is carried forward by the recti and obliqui abdominis, and downward by the psoae and iliaci interni, and the leg by the long flexor and the anterior peronoeus, a fall would be the immediate result, unless the knee, to preserve equilibrium, were somewhat bent, and the other foot at the same time began to assume the same action. While the toes, therefore, are forcibly impelled by their flexors to the ground, the two gastrocnemii, the anterior and posterior tibiales, and the peronaei, elevate the foot with the sole backward, and bend the knee, and the psoas and iliacus raise and extend the whole member.

Running differs from progression, not only in velocity, but in the mode of its accomplishment. Not only are the pelvic extremities more inflected and moved than in mere walking, but they remain inflected. Thus, while the trunk is inclined forward on the pelvic extremities by the recti cruris, the psoae and iliaci, the two latter with the pectinaeus longus, the adductor longus and brevis, and the tensor, are employed to inflect the thigh, the semitendinosus, semimembranosus, and biceps to inflect the leg, and the anterior tibialis, great and small extensors of the toes, and extensor of the great toe, are employed to bend the foot and the phalanges on the metatarsal bones. The last action is essential to running, which is always most perfect on the tip of the foot. In this movement also the centre of gravity is constantly undergoing change, and is not only carried forward, but makes a sort of undulating motion on each side, and above and below the plane of motion. This is the effect of the pectoral extremities being employed to balance the person.

In leaping, the pelvic extremities are much inflected, and the sole of the foot rendered tense, by the gastrocnemius, solaeus, tibiales, and peronaei, while the extensors are employed to raise the phalangeal part of the foot; when the person is forcibly impelled forward by the gastrocnemius, solaeus, the leg suddenly contracting on the cruraeus in the thigh, and the glutaeus, semitendinosus, semimembranosus, and biceps in the pelvis.

In dancing, the muscles are made to co-operate in producing a number of complicated motions. In most of the motions composing the dances practised in ordinary society, while the muscles of the pectoral extremities are employed in balancing the person, and those of the trunk in maintaining it in the erect attitude, the flexors and extensors are employed to diduct, inflect, or extend; to cross the extremities with more or less rapidity; and, while the extensors and tibialis anticus elevate the person on tip-toe, the lateral peronaei are employed to evert the foot and point the toes.

CHAP. II. THE ORGANS OF SENSATION.

The organs of sensation may be distinguished into two orders, according as their province is to recognise general or peculiar affections and qualities in external objects. Thus, while it is the purpose of touch to recognise the consistency, shape, and resistance of bodies, it communicates no information regarding their colour, smell, or taste, or the effects which their collision produces in the vibrations of the atmosphere. With these affections of the material world man becomes acquainted by means of organs of a peculiar construction, and adapted to receive the impressions occasioned by these qualities. These organs are, for smell, the nostrils and their appendages; for colour and the general purposes of sight, the eye; for taste, the palate and mouth; and for sound, the ear. For the purposes of common sensation the skin is the agent; but on the structure of this membrane it is unnecessary to add any thing to what has been already said in the General Anatomy, unless that in certain regions, for instance the tips of the fingers, the erectile arrangement of the capillaries, with a minute distribution of nerves, and great thinness of cuticle, communicates the delicacy necessary to the refined purposes of tact.

SECT. I. THE ORGAN OF SMELL; THE NASAL CAVITIES.

The organ of smell consists of an external part for receiving and transmitting substances capable of producing the sensation of smell; and an internal part, in which this sensation takes place.

The nose (nasus), which constitutes the external part, is a pyramidal eminence, bounded above by the forehead, below by the upper lip, and on the sides by the orbits and cheeks. It has two anterior-inferior oval-shaped lateral openings named the nostrils (nares), separated by a partition. It consists above of the nasal bones and the nasal processes of the superior maxillary bones, covered by periosteum, cellular tissue, part of the compressor narium, and skin. Below, it consists of membranous fibro-cartilages, attached to the nasal bone and superior maxillary above and behind, and supported by a middle cartilage (septum narium), which rests on the fissure of the vomer below, and is fixed to the vertical plate of the ethmoid bone above, and to which is attached a slip of fibro-cartilage before, named columna nasi. The lateral fibro-cartilages, which are occasionally named wings (aloe nasi, pinnoe nasi), covered by cellular tissue, muscles, and skin, liberally supplied by blood-vessels and sebaceous follicles, are moved by the levator, compressor, and two depressors. These parts, with the middle septum and columna, are lined by a form of mucous membrane named the pituitary or Schneiderian.

To what was already said of the nasal cavities under the head of Osteology it is superfluous to add any thing, unless what relates to the lining membrane, the distribution of which is exactly according to the extent of the bony walls of these cavities and their subdivisions.

This membrane consists of two layers; a fibrous, which is the periosteum or perichondrium of the nasal cavities; and a mucous, resembling the other forms of this tissue. It is soft, spongy, red, and more or less vascular, with an attached and a free surface, the latter secreting the thin mucus necessary to preserve the membrane in a proper state for receiving odorous impressions. In this membrane[7:2:798] mucous glands are indistinct; but we recognise minute orifices or pores, which maybe the follicular cavities ’on a small scale, or the orifices into which the mucous fluid is poured after secretion by the arteries.

This mucous membrane is supplied from the internal maxillary artery with blood-vessels, which are at once abundant and superficial. These anastomose with the infra-orbital and ethmoidal branches of the ophthalmic artery and some others of the internal carotid. On these circumstances depends the frequency of hemorrhages from this membrane in early life, while the capillary system is energetically employed in the enlargement of the cranio-facial region; and in advanced life, when venous plethora is most conspicuously evident in the vessels of the head.

The nerves which supply the nasal cavities are the first or olfacient nerves principally, the internal nasal of the ophthalmic, and several branches derived from the sphenopalatine ganglion, the frontal, the great palatine, and the vidian. The distribution of these nerves has been beautifully represented by Scarpa (Annot. Acad.), from whom fig. 1 and 2 of Plate XXXIΠ. are imitated.

SECT. II. THE ORGAN OF VISION; THE EYES.

The eyes, placed in the orbits, are distinguished into the globes of the eyes, and their appendages.

The globe or ball of the eye, situate at the base of the orbit, has a spheroidal shape, with the antero-posterior diameter longest, and varying in the adult from 10 to 11 lines. The direction of the eye differs from that of the orbit, the axis of which is oblique and convergent behind, while that of the two eyes is parallel.

The eye-ball (bulbus oculi) consists of several membranes, containing fluid or semifluid substances, denominated humours. The external and strongest is the sclerotic, with the cornea enchased in its anterior aperture; next is the choroid and retina; and the iris, a circular membrane, with an annular aperture, is placed transversely across, dividing the cavity into anterior and posterior chambers. The humours are the vitreous, the crystalline lens, and the aqueous humour.

The sclerotic, sometimes named cornea opaca, in contradistinction to the clear cornea, is shaped like a spherical shell, truncated before, and is estimated to occupy about four fifths of the globe. Its exterior surface is covered by the adipose matter of the orbit behind, and by the tendons of the muscles of the eye and the ophthalmic conjunctiva before. Its inner concave surface is lined by the choroid coat. In its anterior opening, which is about six or seven lines diameter, the cornea is enchased by imbrication of the sclerotic; and in a posterior opening about one and a half line in diameter, the ophthalmic end of the optic nerve is fixed. It is fibrous in structure, becoming translucent when immersed in oil of turpentine. Its vessels are generally colourless, and it appears void of nerves.

The cornea, often named the clear or transparent cornea (cornea lucida), to distinguish it from the opaque cornea or sclerotic, which was supposed by the old anatomists to be of the same nature, is a segment of a smaller sphere than that of the sclerotic, attached to its anterior aperture, and occupying the anterior fifth of the eyeball. Before it is covered by a thin pellicle continued from the conjunctiva, behind by the anterior part of the membrane of the aqueous humour; and its circumference is inseparably enchased within that of the anterior aperture of the sclerotic. The cornea consists of several concentric layers of transparent homogeneous matter, void of vessels or nerves, closely united, but separating and becoming opaque after death.

The choroid coat (tunica choroides) lines the inner surface of the sclerotic, to which it adheres loosely, except at the insertion of the optic nerve, where it has a posterior opening, yet may be easily detached. The margin of its anterior opening, which is large, adheres to the ciliary circle and processes, and appears to be continuous with the iris. The outer surface is covered by a brownish-black viscid matter, which partly adheres to the inner surface of the sclerotic. The inner surface, over which the retina is extended without adhesion, is covered by the same brownish-black matter; but of this the retina receives none, as the sclerotic. The choroid is a thin membrane, of a grayish colour when deprived of its brown pigment, translucent, homogeneous, and, so far as observation goes, void of fibres, but liberally supplied by minute blood-vessels, partly from the long, chiefly from the posterior ciliaries, which, dividing on its outer surface into numerous ramifications, mutually approximate, and anastomosing, form a network of quadrilateral and trapezoidal meshes. The tunica Puyschiana is imaginary, unless this arrangement of capillary vessels be such.

From these vessels is derived the brownish-black matter (pigmentum, nigrum) with which the retinal surface of the choroid is covered. Its appearance on the convex or sclerotic surface is the effect of cadaveric transudation. The nature of this colouring matter is imperfectly known. When first secreted it is brown, but becomes black successively as it continues. It is not affected by the action of light or caloric, and undergoes no change from the operation of the mineral acids, aqua potassae, ammonia, and alcohol. It appears to consist chiefly of carbonaceous matter. Menghini asserts that he has obtained from it minute particles of iron attracted by the magnet.

The anterior orifice of the choroid is firmly connected to a thick ring of grayish pulpy substance, and forming the point at which the sclerotic and cornea without, and the iris within, are united. This ring, named the ciliary circle (ligamentum ciliare), is readily detached from the sclerotic. Its structure is unknown.

Posterior to this is a range of prominent minute bodies, with free extremities, lying over the crystalline lens, varying in number from seventy to eighty. These are the ciliary processes (processus ciliares). They are trilateral-prismatic in shape, about a line and a half long, more distinct and longer in the human eye than in those of most brute animals. Their intimate structure is not very well known; but they are highly vascular, and their vessels appear to be capable of occasional erection. (Plate XXX. fig. 4∙)

Anterior to the ciliary circle is the iris, a circular membrane, placed in the transverse vertical position, with anterior and posterior surfaces, and a circular opening in the centre. The exterior ciliary margin (annulus major) is attached, as already stated, to the ciliary circle. The inner or pupillar (annulus minor) is free, and forms what is named the pupil of the eye. The anterior surface is marked by a variety of colours, blue, gray, or black, brown, or that peculiar brownish-black named hazel, and which are not unfrequently allied with the tints of the skin and hair. The same surface presents radiating lines, which pass from the small to the large circle diverging. Both appearances are produced by vascular arrangement. The posterior surface of the iris, which has been distinguished as a separate membrane under the name of uvea, is covered by the same dark-coloured matter secreted by the Choroid, generally more abundant, and of a deeper tint, than the pigment of that membrane. When this is removed by washing, the observer recognises the radiated streaks impressed by the ciliary processes. (Fig. 4.) [7:2:799]The different characters of these two surfaces have induced some anatomists to distinguish the iris into anterior 'and posterior membranes. Though it has some thickness, this is perhaps a fanciful refinement. The anterior surface, which is continuous with the membrane of the aqueous humour, is different from the posterior, which is continuous with the ciliary circle and choroid. The structure of the iris is chiefly vascular, and its vessels have an; erectile arrangement. The long ciliaries, from which these vessels are derived, divide each at the ciliary body into two branches, which divaricating at obtuse angles, unite with several of the anterior ciliaries, and form with them, beyond the ciliary ligament at the large circumference of the iris, an arterial circle. From this arise smaller branches, which, crossing, unite and form within this a second smaller arterial circle, midway between the ciliary and central margin; and from the concavity of this proceed very minute vessels, which radiate in a flexuous manner, and converge towards the pupil, where, anastomosing most minutely, they form a third circle—the marginal ring of that aperture.

It is chiefly in the middle and inner anastomosing circles that the vessels assume the erectile arrangement; and on this circumstance, and not on that of muscular fibres, so often, so positively, so inconsistently, and so erroneously maintained to exist in the iris, does the mobility of that singular membrane depend. On exposure to direct or bright light, on the application of vinegar, alcohol, or any stimulating substance to the eye, and during the presence of inflammation, the erectile capillaries, distended with blood, arc elongated, and necessarily contract the pupillary aperture. In the dark, under the influence of henbane (hyoscyamus niger), deadly night-shade (atropa belladonna), and some other narcotics, and when the retina is insensible, these vessels seem to lose their faculty of distension, and, perfectly empty and shrunk, allow the pupillar margin to approach the ciliary.

The retina, which is the third and internal tunic, is of the same shape as the choroid, thin, like cobweb, whitish, translucent, inclining to transparent, and very delicate. Its extreme tenuity and looseness from the choroid causes it to collapse unless inspected under water, when it may be unfolded and expanded for examination. Its outer surface is covered by a very delicate membrane, visible only in a very recent eye, discovered by Mr Jacob of Dublin. It is almost void of red vessels, unless at the part where the optic nerve enters, where one or two from the central artery may be seen. The others are colourless. The assertion that this membrane is an expansion or production from the optic nerve, seems to be gratuitous; for it bears no resemblance to nervous matter, or to the appearance of the optic nerve. It appears to be simply a peculiarly delicate transparent web, fitted to receive the impressions of luminous rays, and to communicate them to the optic nerve, with which it is continuous.

On this membrane, about two lines on the temporal side of the optic nerve, and in the axis of the ball, is a circular yellow spot (macula lutea), from about a line to a line and a half in diameter, with a minute point or hole in its centre (foramen centrale). At this part the retina is much thinner than at any other; and even in the most recent eyes it presents loose folds, which Bichat regards as cadaveric. The yellow spot and its central hole are seen in none of the mammalia except man and the monkeys.

The vitreous humour, occupying about three posterior fourths of the eye, is spherical and convex behind and on its lateral circumference, but concave before for receiving the posterior part of the crystalline lens. Contiguous only to the retina, it is attached to the coats by the branch sent from the central artery to the lens. It is transparent, and consists of two parts, an investing membrane, the hyaloid (membrana hyaloidea), and inclosed fluid. This membrane is not single, but, sending numerous partitions from its inner surface, forms an assemblage of cells in which the fluid is contained. These facts may be demonstrated by incision, bruising the humour, by congelation, or by boiling it. Before, at the outline of the lens, this membrane divides into two folds, one of which is stretched before the capsule, and the other behind. The trilateral-prismatic space resulting from this separation is completed by the capsule, and forms the circular canal of Petit, which is without fluid, and which is demonstrated by inflation. On the anterior fold the ciliary processes are stretched. The structure of the hyaloid membrane is little known; but it is believed to consist of exhalant arteries and colourless veins.

The hyaloid fluid may be separated from the membrane either by incisions or compressing it between two folds of linen. It then has the appearance of a clear but somewhat viscid fluid, like gum diluted with water. Though rendered slightly turbid by boiling water, acids, and alcohol, it does not coagulate,—a phenomenon which is to be ascribed to the small proportion of albumen which it contains. According to the analysis of Berzelius, 100 parts contain 98∙4 of water, ∙16 of albumen, 1∙42 of muriates and lactates, and only 3 j θth of a part of soda.

The crystalline lens, which is transparent and shaped like an oblate spheroid, is situate in the posterior chamber, and in the anterior depression of the vitreous humour, to which the convexity of its posterior surface corresponds. Before also it is prominent and convex; and it is partially covered by the free extremities of the ciliary processes. It consists of two parts, an inclosing capsule and a lens proper.

The capsule is usually distinguished into anterior and posterior walls, both covered by hyaloid membrane, both transparent, and both firm and resisting. By boiling water, alcohol, or the acids, it is rendered opaque, whitish, and horny; and it becomes yellow by contact with the air.

The lens, which is perfectly transparent, consists of two portions; an exterior, peripheral, thick, soft, adhesive, and easily removed; an interior, central, solid, and consisting of concentric plates. Both are indurated and rendered opaque by boiling water, alcohol, and dilute acids; but the central nucleus is the firmest. When dried in the air it becomes yellowish, but retains its transparency, and may be preserved for years. These phenomena are to be ascribed to the presence of a peculiar form of albumen. According to the analysis of Berzelius, 100 parts of the substance of the lens consist of 58∙ of water 35∙9 of peculiar matter, chiefly albuminous, 2∙4 of muriates, lactates, and animal matter soluble in alcohol, l∙3 of animal matter soluble in water, and 2∙4 of membrane.

The lens possesses a high refracting power; and its chief use is to concentrate the luminous rays within the eye, so as to represent distinctly the image of visible objects on the retina. Spherical and transparent in early life, it is flattened and acquires a yellowish tint in old age.

Between the capsule and lens is found occasionally a fluid which has been named liquor Morgagni. It appears to be the effect of transudation.

On the structure of the lens, whether organic or not, anatomists vary. Vessels have not been recognised in it; and the most rational view is, that it is the product of an organic action probably in the capsule.

. The aqueous humour is contained in the anterior chamber, and in that part of the posterior which surrounds the anterior surface of the lens and vitreous humour. It consists[7:2:800] of 98.10 parts in the 100 of water, a trace of albumen, and about 2 parts of muriates and lactates of soda. It is contained in a membrane, which lines the posterior surface of the cornea, and is supposed to cover the anterior surface of the iris. This, however, is questionable. In 1768 a membrane of this kind was described by Demours and Deseemet, both of whom claimed the discovery with great eagerness and some animosity. These rival anatomists appear to have forgotten that the aqueous humour may be secreted as well by the cornea and iris as by a proper membrane.

The relation of the coats and humours of the eye to each other may be understood by the diagram (fig. 3, Plate XXX.), where A is the anterior chamber, P the posterior, L the lens, and c, c the ciliary processes. The other parts are easily understood from the foregoing description.

The eye is supplied with blood chiefly by the ophthalmic artery.

The eyeball, thus constituted, is moved in different directions by six muscles, is moistened externally by fluid •secreted from a particular gland, and is protected from external bodies by the eyelids and their appendages.

Of the muscles, four are straight and two oblique. The former (attollens, depressor, adductor, abductor), attached to the margin of the optic hole, and terminating in tendons inserted into the superior, inferior, nasal, and temporal parts of the eyeball, raise, depress, adduct and abduct the organ. Of the two latter, the superior oblique (troch-ledris), which is attached to the margin of the same hole, passes through a pulley-like cartilage at the inner margin of the vault of the orbit, and is inserted into the internal region of the ball, rolls the eye forward and inward, and turns the pupil outwards and downwards; while the inferior oblique, attached to the orbitar process of the superior maxillary bone, and inserted between the adductor and the optic nerve, rolls it forwards and turns the pupil upwards. These muscles, which occupy the apex of the orbit, are surrounded by a thick cushion of fat, on which the eyeball rolls in its movements. (Plate XXXIII. fig. 6.)

In the hollow, at the outer temporal region of the orbitar vault, is placed the lacrymal gland, a granular grayish body, about the size of a bean, consisting of lobules, with arteries in the intermediate furrows, derived from a branch of the ophthalmic, and accompanying veins. (Plate XXXIII. fig. 5 and 7, G, g.) These constituent lobules have been represented, on the authority of Steno in the ox, and the elder Monro in the human subject, to terminate in 7 or 8 minute excretory ducts, opening on the conjunctiva. In man, however, they were sought in vain by Duverney, Morgagni, Haller, and Zinn; and neither Portal nor Bichat have been able to satisfy themselves of the existence of these ducts. It is nevertheless certain that the lacrymal gland secretes the tears, and that the latter issue from its lobules.

The eyes are covered anteriorly by two musculo-mem- branous folds named the eyelids (palpebrae), attached to the margins of the orbit, and forming by their free margin the palpebral opening, with commissures at each angle (canthus nasalis, et canthus temporalis).

The upper eyelid, which is large, is bounded above by the eyebrow (supercilium), a cutaneous eminence, arched transversely, covered with hairs, and with the corrugator supercilii attached to its nasal end. Between each eyebrow is a smooth space, named the glabella or mesophryon. Into the upper eyelid the levator (fig. 5, L) is inserted.

Each eyelid consists of skin externally, mucous membrane within (conjunctiva), intermediate cellular tissue, muscle, and a fibrous membrane, attached by one margin to the base of the orbit, and terminating by the other in the tarsal fibro-cartilages. These are crescentic bodies placed in the free margin of the eyelids, and by then-firmness and elasticity giving the requisite tension to the eyelids when the orbicular muscle acts, or the levator is relaxed. The cutaneous border of the tarsi is occupied by a range of short, firm hairs, named the eyelashes (cilia). In the mucous borders are the orifices of the tarsal or Meibomian follicles, of the same character as the muciparous follicles generally. These are placed in the substance of the eyelid, beneath the conjunctiva, and behind the tarsal fibro-cartilages. From the inner surface of the eyelids the palpebral conjunctiva is continued over the anterior part of the sclerotic and cornea, forming the ophthalmic conjunctiva.

In the nasal angle is lodged a minute red body, named the caruncle (caruncula lacrymalis), chiefly consisting of filamentous tissue and vessels covered by mucous membrane; and behind this is a fold of the membrane, which has been named membrana nictitans, large in the lower animals, but often so imperfect in man as to be merely rudimentary.

At the nasal end of each eyelid is a minute capillary] orifice which leads into a horizontal canal, terminating in t a membranous sac lodged in the depression of the lacrymal bone. These orifices, which are named the puncta lacry-malia (p, p, fig. 5), are the superior or palpebral openings of the lacrymal sac and passages, the lower aperture of which is found in the inferior nasal meatus. The tears effused from the lacrymal gland at the temporal region of the orbit are carried, by the frequent action of the orbicular muscle, over the ball, till they reach the nasal angle, where they are gradually absorbed by the capillary orifices of the puncta, and conveyed into the sac, and eventually to the nose.

The eye derives nerves from six different sources, all of which, however, may be distinguished into three classes, the sensitive, motive, and entrophic nerves. The first consists of the second, optic or the proper visual nerves. The second class comprehends the third, fourth, and sixth nerves, of which the third or oculo-muscular are distributed to the levator palpebrae superioris, the attollens, the adductor, the depressor, and the obliquus inferior ; the fourth is entirely distributed to the obliquus superior ; while the sixth pair are confined to the abductor. The third class of nerves is derived from the ophthalmic or quadrilateral ganglion, which is formed chiefly from the junction of a sub-branch of the naso-ocular branch of the first or ophthalmic division of the fifth pair, with a small branch of the third nerve. From this arise a small superior cluster of three nerves adhering to the optic, and a large inferior cluster of eight or ten nerves, which quickly join the ciliary arteries, and are with them distributed in the ciliary circle and posterior part of the iris. ( Plate XXXIII. fig. 7.) From the other branch of the naso-ocular nerve, the caruncle and lacrymal canal, with the orbicular muscle and epicranius on the one hand, and the lacrymal gland on the other, receive nervous filaments.

SECT. III. THE ORGAN OF HEARING; THE EAR.

The organ of hearing consists of the auricle or external ear, with the ear-hole; the middle ear, including the tympanal cavity and its appendages; and the internal ear or labyrinth.

The auricle is a fibro-cartilaginous substance, moulded into a conchoidal shape, covered by skin, attached to the cranium by ligaments, and susceptible of motion by muscles. It is common to distinguish in it the following parts. The helix, a semicircular eminence above the earhole; the groove of the helix below it; the antihelix, an eminence commencing in the groove by a superior, broad, [7:2:801]oblique portion, and an inferior, narrow, horizontal one; the fossa navicularis; the tragus, an anterior eminence below; the antitragtis, a smaller eminence behind; the lobule, a pendulous body at the base behind; and, lastly, the concha, a deep conoidal cavity leading to the ear-hole.

The latter is a canal about 10 or 12 lines long in the adult. Twisted at first obliquely forward and upward, it bends slightly backwards and downwards, forming a Convexity of incurvation above, and a concavity below. Though the extremities are large, the middle is contracted; and it cannot be termed cylindrical, for its section is elliptical or oval. The structure of this tube is fibro-cartilaginous externally where it adheres to the bone, lined by skin passing into mucous membrane, and occupied by minute follicles (glandules ceruminosa;), which secrete the wax (cerumen) formed in this canal. The nature of this secretion is imperfectly known. Though, like oil, it stains paper, it is partly soluble in tepid water, and forms with it a yellow emulsion. It is secreted at first fluid, and acquires consistence by exposure to air and admixture with dust. Alcohol has. little influence on it. The internal extremity of the auditory canal is bounded by the vertical membrane of the tympanum.

Within this is the tympanal cavity, a space of an irregular cylindrical shape, directed obliquely, nearly in the axis of the pyramidal portion, in the base of which it is contained. This cavity is shut up externally by the vertical tympanal membrane (membrana tympani), and is bounded within by the bony partition which separates it from the labyrinth. The membrana, which is oval-shaped, or nearly round, and attached to the margin of the meatus externus, is directed obliquely downwards and inwards, and is so delicate that it is difficult to determine its structure in the human subject. In the elephant, however, and Other large animals, it presents radiating fibres, which are believed to be muscular (Plate XXXVII. fig. 14); and Sir E. Home represents it as such not only in the elephant and whale, but in the human subject. The outer part is evidently a sort of epidermis, continuous with that of the canal; the inner is a mucous epidermis, continuous with that of the tympanal cavity; and between these the muscular fibres are interposed.

ι The tympanal cavity communicates behind with the mastoid cells, and before and internally by the Eustachian tube, with the pharynx. This tube is estimated to be two inches in length, of which one and a half is in the bone of the pyramid, and about half an inch at its extremity, with the upper side completed by cartilage. Narrow at the tympanal end, it becomes wide and capacious towards the pharyngeal, and presents at length a free open extremity, forming a fissure at the upper and lateral part of the pharynx. The cartilaginous end is covered by mucous membrane continuous with the pharyngeal, and is surrounded by the peristaphylini, the action of which is believed to separate the walls of the aperture. Within the tube, and towards the tympanal end, this membrane parts with its pharyngeal spongy character, and becomes thin and semitransparent where it lines the bone. The same kind of membrane, partaking of the characters of periosteum and mucous, is continued over the tympanal cavity, and into the mastoid cells.

Above the Eustachian tube is a thin osseous plate, which separates it from a small canal, convex below, concave above, and which, commencing in the fissure between the squamous and pyramidal portions, terminates in the tympanal cavity. In this canal is lodged the internal muscle of the malleus, one of the tympanal bones.

These are four in number, very minute, and denominated, from their mechanical figures, the hammer (mal letis), the anvil (incus), the lenticular or round bone (os orbiculare), and the stirrup (stapes). Of these the malleus is attached to the vertical membrane by its handle, while its head is articulated with the body of the incus. The latter presents two limbs or branches, to the larger of which the stapes is articulated by the interposition of the lenticular bone; while the base of the former rests on the membrane of the foramen ovale. These articulations are secured by capsules, which allow the bones to move freely on each other; and for this purpose the stapes is provided with one muscle, and the malleus with two, an internal already mentioned, and an external passing from the spinous process of the sphenoid bone to the slender process of the malleus. On the motions of these, however, and their part in the process of hearing, we have only conjectural statements.

The internal bony wall of the tympanal cavity presents two apertures and a convex intermediate eminence. Of the apertures, the first, which is named the oval or vestibular aperture (foramen ovale, fenestra ovalis), is situate above, oval transversely, with its great diameter horizontal antero-posterior. It communicates with the vestibule, but is closed by a fine membrane, to which the base of the stapes is fixed, and for the insertion of which its margin is grooved. The oval aperture is bounded above by a round prominence, corresponding within to the Fallopian aqueduct, and below by a large convex eminence named the promontory (promontorium), which indicates the situation of the cavity named the vestibule. Before and above the promontory is the extremity of the thin osseous plate which separates the Eustachian tube from the canal of the internal muscle of the malleus ; and behind is an oblique cavity, which is placed between the lower entrance of the mastoid cells and the pyramid. Below the promontory is the round or cochlear aperture (foramen rotundum, fenestra rotunda), trilateral in early life rather than round, and still preserving in the adult the tendency to this shape; smaller than the oval, and directed backwards and outwards. The round aperture is shut by a membrane, the direction of which is oblique to that of the tympanum, and one side of which is towards that cavity, while the other forms part of the cochlea.

At the upper part of the tympanum is a triangularshaped opening, which leads into a rough short canal, ι terminating in the mastoid cells. These are analogous to the cells of the ethmoid, sphenoid, and occipital bones. They are lined by fibro-mucous membrane, and their use is to afford a posterior sonorous apartment for the vibrations produced in the tympanal cavity.

Near this triangular opening is a small bony process named the pyramidal, in which is a canal for the fleshy part of the stapedius, while the tendon issues from its orifice. Near the base of the pyramidal process is the hole by which the nerve of the tympanum (chorda tympani) passes through the glenoid fissure.

The labyrinth consists of the vestibule, three semicircular canals, and the cochlea.

By removing the stapes and stapedial membrane the oval aperture is opened, and communicates with the vestibule. This cavity, which is irregular in shape, about the size of a grain of barley, is bounded without by the tympanum, within by the internal auditory canal, before by the cochlea, behind by the semicircular canals, and above and below by the solid bone of the pyramid. It is lined by a membrane common to the whole labyrinth. Besides the oval aperture by which it is separated from the tympanum, it has, above, the two anterior openings (ampulluloe) of the superior vertical and horizontal canals; behind, the two openings (ampullulce) proper to the posterior vertical and horizontal canals, and the common opening of the [7:2:802]two vertical canals; and before and below, the orifice of the external scala cochleae.

There is still another aperture, which leads into a canal discovered by Cotugno, named the aqueduct of the vestibule. This, which, though distinct in some subjects, is almost imperceptible in others, is near the common orifice of the vertical canals; and from it the aqueduct proceeds first upwards, where it is narrow, then backwards and downwards, widening, and terminates in the fissure on the posterior surface of the pyramidal portion.

The semicircular canals, situate behind the vestibule, are three in number, two vertical and one horizontal. Of the former, one is superior, inclosing by its curvature the substance of the pyramid, and forming a convexity in the adult, very distinct in the foetus; while the other, which is posterior but inferior, is placed with its plane corresponding to that of the posterior surface of the pyramid. The third is placed horizontally between the other two, forming a curvature with the convexity towards the base of the pyramid. (Plate XXXIII. fig. 8, 9, and 10.)

Though denominated semicircular, these canals are larger than semicircular, and may be compared to hollow cylinders, incurvated so as to form large circular segments. Each canal has an enlarged extremity named ampullula ; and as these two vertical canals have one in common, there are five ampullulae. They are lined by the common labyrinthine membrane, and contain a pellucid fluid.

The cochlea, which forms the third part of the labyrinth, is a conical canal turned spirally within itself, so that its base is at the lower part of the vestibule, and its apex at the anterior side of the pyramid, with the orifices for the auditory nerve inclosed in the centre of its turns, while the convexity is directed towards the lower margin of the pyramid. The cochlear canal is divided longitudinally by a thin sharp-edged plate, half bony half membranous, into two independent cavities, the superior of which communicates with the vestibule, while the inferior is bounded by the membrane of the round aperture. These cavities are distinguished as the vestibular and tympanal (scala vestibuli and scala tympani) respectively. At the top they terminate in a common cavity named the funnel (jnfundibulum). Both are lined by a delicate membrane, in which are contained the ramified filaments of the eighth or auditory nerve. (Plate XXXIII. fig. 10.)

In the tympanal scala, near the round hole, is a minute aperture leading to a narrow canal, which gradually enlarges as it ascends, till it terminates by a slit on the posterior surface of the pyramidal portion, as formerly mentioned. ' This is the aqueduct of the cochlea, first described, like that of the vestibule, by Cotugno.

These different cavities are supplied with blood chiefly >from minute branches of the auditory, a vessel generally derived from the basilar trunk or the vertebral arteries. From the meningeal artery also minute branches enter the auditory canal, and anastomose with those of the auditory artery; and the internal carotid sends to the membrane of the tympanal cavity a branch, the capillary ramifications of which anastomose with those derived from the pharyngeal, transmitted by the walls of the Eustachian tube.

The eighth or the proper auditory nerve enters the cochlea by several minute apertures in the internal meatus, and is divided into two fasciculi, of which the posterior and largest is expanded in the form of soft pulpy brush-like filaments, like a hair-pencil, in a pellucid fluid, in the cochlea ; while the smallest, which is anterior, is distributed partly to the bottom of the hemispherical cavity of the vestibule, partly to the beginning of the spiral lamina. “The tympanal cavity is chiefly for the purpose of conveying and augmenting the intensity of sonorous vibrations, while the shape of the auricle is ⅛upposed to collect' them. But of the mechanism of its operation we know nothing satisfactory. The essential part of the organ of hearing is the labyrinth.

SECT. IV. THE ORGAN OF TASTE.

It is impossible to define the exact limits of the sense of taste. More or less diffused over the cavity of the mouth, it is particularly confined to the tongue and palate. The former, nevertheless, is remarkable for being a muscular organ, which combines with the faculty of taste the power of prehension and transmission of the alimentary articles both during and after mastication, and is further an essential agent in the faculty of articulation. It is requisite, therefore, to give a short account of the mouth, the palate, and the tongue.

a. The mouth is the cavity formed by the lips before, the pharynx and isthmus faucium behind, the palatine vault above, the intramaxillary membrane and muscles below, and on the sides by the cheeks. Its horizontal direction may be regarded as one among other proofs of the necessity of the erect biped attitude.

The mouth is lined by a mucous membrane, soft, spongy, red, and vascular. It may be traced from the inner or alveolar surface of the lips to the inner surface of the cheeks on each side over the gums, where it is continuous with that of the alveolar folliculi, over the inner surface of each maxillary ramus, and the attached muscles and glands below, until it is identified with that of the tongue, and above over the palatine vault back to the uvula. In these several points, though its organization is the same, its mechanical arrangement varies considerably as the parts are fixed or movable. Thus, on the palatine vault and at the gums it is tense, and adheres pretty firmly to the fibrous layers forming the periosteum of these parts. In the angular space between the lips and gums, however, in that between the inner surface of the alveolar arch, and all over the lower part of the mouth, where it is connected to the inferior surface of the tongue, it is extensive, loose, moves easily over an abundant layer of filamentous tissue, and is generally disposed in irregular folds. Adhering to the internal spine of the lower jaw, a fold or duplicature containing condensedfilamentous tissue is reflected, to be attached to the median line of the tongue, and forms the frenum of that organ. In all points it abounds with muciparous follicles. It also presents on each side of the tongue the orifices of the sublingual glands.

The mouth has two outlets, an anterior or facial formed 1 by the lips (labia), and a posterior or pharyngeal formed by the velum palatinum and its appendages.

The lips are musculo-membranous folds, attached all' round to the superior and inferior jaw-bones, above and below the alveolar arches, and parted by a transverse opening or fissure into upper and lower, with right and left commissures or angles (canthi). In the Negro race they are particularly bulky and flaccid, with their free margins (prolabia) much everted; but in the Asio-Euro-pean they are thinner, and more constricted.

Each lip consists externally of skin continuous with that of the face, internally of mucous membrane continuous with that of the mouth, with interposed filamentous tissue and muscles, well supplied by blood-vessels and nerves.

The point of union between the skin and oral mucous membrane is marked by a rounded edge, covered by a thin, vermilion-red, soft and delicate pellicle, extending between [7:2:803]each canthus. This, which is sometimes named the lips proper (lαbiola), is the prolabium. The blood-vessels distributed to this part of the lips have an erectile arrangement The marginal region of the lips between the skin and mucous membrane is occupied by the orbicular muscle. Above are the labial ends of the common levators (levator labii superioris aloeque nasi), the proper levators (levator labii superioris), the small zygomatics (zygomaticus minor), and the naso-labial (nasalis labii superioris). Below are the two depressors of the lower lip. At the angles are placed the buccinators, the depressors of the angles, the canine muscle (levator anguli oris), and the large zygomatics.

The lips are supplied with blood from the branches of the external carotid. The external maxillary sends a large branch over the angle of the inferior jaw, upwards and forwards to the labial commissures on each side. This vessel, which is generally named the labial, sends oft' two, a superior and inferior labial, which are subdivided into numerous minute branches, anastomosing freely with each other, and with the submental and inferior dental branches. They open freely into the capillary veins, constituting a species of erectile tissue.

The lips derive their nerves partly from the superior maxillary, partly from the anterior or mental division of the inferior maxillary, with anastomotic communications from the 8th or facial nerve.

b. The posterior or pharyngeal outlet of the mouth (isthmus faucium) is formed by the movable or soft palate (velum palatinum), a membranous fold attached to the posterior margin of the palatine quadrilateral bones, and hanging with its free margin downwards. This curtain, which has two surfaces, an anterior or oral and a posterior or pharygneal, is shaped like a double arch, meeting on the mesial plane, where it terminates in an elongated conical prominence, supposed to resemble a grape suspended by its stalk, and denominated therefore uvula (ora<f>υλr1), but which, with the lateral arches,bears a closer resemblance to the descending cusp of a Gothic window. From this central process the arch rises on each side; and when it passes to the outer edge of the palate-bone on each side, it is supported by two musculo-membranous vertical columns, united at the top, but separating and forming an intermediate cavity, in which the tonsil on each side (amygdala) is contained.

The palatine curtain consists of two folds of mucous membrane, with interposed filamentous tissue and muscular fibres. The anterior mucous membrane is of the same character with that of the mouth, with which it is continuous. The posterior, which is continuous with the nasal mucous membrane, partakes of the characters of that tissue, and is redder and more vascular. These two meet in the lower margin of the velum, and pass into each other. Both arc well supplied with mucous follicles, but the anterior or oral division most copiously.

These mucous membranes rest on filamentous tissue; and beneath this we find, in the middle, the levator or azygos uvuloe, and on the sides the levator of the soft palate (peristaphylinus internus), which are expanded in the velum. The anterior pillar consists of mucous membrane enveloping the fibres of the constrictor isthmi faucium ; the posterior incloses those of the pharyngo-staphylinus ; and both expanding into the velum, augment its thickness and regulate its motions.

Between the internal peristaphylini, which are immediately below the pituitary or posterior mucous membrane of the velum and the anterior, is an aponeurotic web, connected with the circumflexi, which, fixed to the margin of the palatine vault, tends to consolidate the velum.

The free margin of the velum forms the upper boundary of the posterior or pharyngeal opening of the mouth, while the upper surface of the base of the tongue forms the lower boundary. The size of this opening, which is usually named the isthmus of the throat (isthmus faucium), varies according to the state of the velum and its uvula. In the act of deglutition the velum and uvula are raised by the peristaphylinus internus and azygos uvulae, and the whole curtain is constricted by the constrictor isthmi faucium and pharyngo-staphylinus. In the act of vomiting it is forcibly drawn up against the posterior nasal openings by these muscles; but notwithstanding this, matters from the stomach are occasionally projected through the nostrils. In singing on false notes the uvula is progressively elevated, as the voice ascends.

In the space between the anterior and posterior pillars are contained the tonsils (tonsilloe, amygdaloe), bounded above by the commissure of the pillars; below by the lateral part of the base of the tongue, where they are continuous with the muciparous glands of that organ; before by part of the constrictor isthmi faucium ; and behind by the pharyngo-staphylinus. The shape varies in different individuals, though their pendulous attachment gives them the oblong spheroidal or almond-like shape. They consist of several lobules, grayish, soft, and of structure similar to that of the muciparous glands of the tongue. The lobules present minute cavities, isolated or mutually communicating, in the recess of which are minute pores, the orifices of the excretory ducts, and from which a watery but viscid liquor may be expressed. In short, each tonsil may be regarded as an assemblage of muciparous glands, destined to secrete fluid for lubricating the throat during the process of deglutition, when it is most abundant.

The chops (buccae) or lateral walls of the mouth consist externally of skin, internally of mucous membrane and of an intermediate layer of muscles imbedded in abundant filamentous and adipose tissue.

The cutaneous covering is in general thin, soft, and peculiarly smooth, with a minutely distributed and abundant capillary system, which approaches in its characters to the erectile.

Beneath the cutaneous covering is the zygomaticus major, the only muscle proper to the cheek, resting on a thick layer of fat; below this is the buccinator, perforated by the parotid duct; and to the filamentous tissue inside, the buccal mucous membrane, furnished with numerous muciparous follicles, adheres. The orifice of the parotid duct is seen opposite the second molar tooth of the superior jaw.

c. The tongue is a longitudinal muscular organ, invested by a mucous membrane provided with numerous papilloe, attached behind to the hyoid bone, below to the mucous membrane of the mouth, and free above and before. It is shaped like a flattened cone, and is distinguished into a base and tip (apex), an upper and a lower surface, and two sides.

The base is somewhat thick and broad, but becomes thin and narrow near the hyoid bone. From about I inch anterior to this, however, to near l£ from the tip, the thickness and breadth are nearly uniform. The tip (apex) is flat and rounded or paraboloid in ordinary circumstances, but may be made by muscular action to taper to an angular point. The upper surface, which is free, presents the lingual mucous membrane divided into right and left halves by a superficial furrow. On this, near its posterior end, is a depression, variable in size, named the foramen coecum, in which are contained the orifices of muciparous follicles. From this on each side proceeds an oblique line diverging forward, and forming -with that of the opposite side an acute angle, with the angular point behind. These an [7:2:804]gular lines, which are variable in shape and disposition, f depend on the elevation resulting from the mucous glands at the base of the organ. The rest of the surface presents the minute conical eminences named papilloe, which belong to the mucous membrane. The lateral margins, which are smooth and void of papilloe, form the transition from the upper free papillated surface to the lower, which is chiefly attached by folds of the oral membrane to the lower region of the mouth.

The tongue consists of various muscles, connected by filamentous tissue, some adipose tissue, and invested by mucous membrane.

The muscles are of two orders, those common to the tongue and contiguous parts, and those proper to the tongue. The common or extrinsic muscles are, the styloglossi, between the styloid process and margins of the tongue; the hyoglossi, between the branches of the hyoid bone and the margins of the tongue; and the genioglossi, from the upper internal mental tuberosities to the lower part of the organ. The proper or intrinsic muscle (lingualis) consists of two parallel layers of muscular fibres running along the lower surface of the organ, and a mass of fleshy fibres irregularly arranged and mutually crossing in all directions, and intermixed with a considerable quantity of soft but elastic oleo-adipose matter.

Of the lingual mucous membrane the most important circumstances are, the leathery thickness and distinctness of its corion and epidermis on the superior surface of the organ, and the papillary eminences with which it is marked.

These papillae may be distinguished into three orders; the irregular or granular at the base, the tubercular or rounded about the middle third, and the conical or pointed at the apex.

The granular papilloe, which vary in number from 10 to 15 or 16, are of a spheroidal or ovoidal shape, and are arranged on each side of the median furrow, obliquely behind the sides of the angle already mentioned. These bodies are evidently muciparous follicles; and it is in general easy to distinguish the orifice of the excretory duct by the eye or a moderate lens. They seem to receive filaments from the glosso-pharyngeal nerves, which enter the tongue immediately beneath these granular glands.

The tubercular papilloe, which are much more numerous, have rounded truncated summits, and occasionally pedunculated stalks. They are irregularly distributed towards the middle, margins, and apex of the tongue, promiscuously with the conical; and their nature is unknown.

The conical or acuminated papilloe, though occupying the two anterior thirds of the lingual surface, are nevertheless most numerous towards its apex, where they are also smallest, and somewhat inclined forward. These papilloe are asserted by the older anatomists to be the terminations of nervous twigs; and Cloquet allows them to be the expansion of the filaments of the lingual nerve. This, however, is an evident relic of the fanciful representations of the older anatomists, and is not supported by inspection. I have examined the structure of the lingual papilloe in many instances, and in none have I seen any ground for the assertion that they consist of nervous filaments. They do not even receive a larger proportion than other parts of the lingual membrane. The papilloe consist chiefly of numerous minute blood-vessels, rather tortuous, and communicating directly with veins enveloped in fine filamentous tissue; and from this they derive their property of erection, while their mucous surface secretes mucus copiously. These papilloe are further the seat of the white fur with which the tongue is liable to be coated in affections of. the stomach. The yellow fur seems to be produced from the mucous surface generally.

The tongue is supplied with blood by the lingual arteries, branches of the external carotids, and by the palatine and tonsillary of the external maxillary. The blood is returned by the superficial vein, the ranine, the lingual, and submental.

The nerves of the tongue are derived from three different sources; the inferior maxillary, or third branch of the fifth pair; the glosso-pharyngeal; and the hypoglossal. From the first it receives the lingual nerve, which, after sending filaments to the sublingual gland, the styloglossus, genioglossus, and proper muscle of the tongue, is distributed chiefly to the upper surface, sides, and apex of the organ. This is believed to be the proper gustatory nerve. From the second it receives a lingual branch, which, passing between the styloglossus and hyoglossus, gives filaments to these, the proper muscle, and the posterior part of the genioglossus, and to the granular papilloe. By means of this nerve the motions of the tongue and pharynx are made to associate. The third, which is distributed chiefly to the muscles attached to the hyoid bone, sends filaments also to the hyoglossus, styloglossus, and chiefly to the genioglossus. The hypoglossal is believed chiefly to preside over the motions of the tongue, and probably those destined for articulation.

The tongue is one of the best examples in the human body, of the felicity with which a single organ may be adapted to a great variety of useful purposes. Endowed with the common sensation of tact, diffused over the body at large, its mucous investment is so organized that it recognises readily the peculiar impressions communicated by sapid bodies. To render it more serviceable in this respect, its muscles make it an organ of prehension, and elongate, contract, inflect, incurvate, or extend it, so as to apply objects placed on its tip to the palate or any part of the mouth. By the same means it becomes an important agent in the prehension of food, and in deglutition, by transmitting the masticated food to the pharynx. Lastly, it is a most essential and necessary organ of speech, and, by the nice motions which it undergoes, enables the human race to pronounce literal sounds and articulate consonants, which without its aid would be unutterable. Of this the letters 1 and r are examples.

d. Connected with the organs of taste are the salivary glands, of which there are three pairs, one on each side of the mesial plane; the parotid, submaxillary, and sublingual.

The parotid, so named from its situation before the ear, is the largest of all the salivary glands. It consists of two parts, the parotid proper, a large oblong mass placed in the deep angular cavity formed by the maxillary ramus and the mastoid process; and the socia parotidis, a large flat irregularly oval mass extending beneath the skin of the face. Partaking of the general characters of glandular structure, it is supplied with blood from the external carotid, by the temporal and transverse facial; its veins open into the external jugular; and it receives numerous nervous filaments from the facial and the ascending branches of the cervical plexus.

It has an excretory duct, named also the duct of Steno (ductus Stenonianus), which, quitting the surface of the gland a little above the middle of the upper margin of the masseter, proceeds horizontally over the tendinous part of that muscle, and, sinking into the filamentous adipose tissue of the cheek, perforates the buccinator, and terminates in the mouth at the level of the second superior molar tooth.

The submaxillary or intramaxillary is smaller than the parotid. Oblong in shape, it is placed on the internal pit [7:2:805]of the lower jaw, bounded by the internal pterygoid and mylo-hyoid above, the lingual nerve, the stylo-glossus and ' hyο-glossus, and the external maxillary artery behind, and below by the latissimus colli and integuments. Blood it derives from the lingual and external maxillary arteries, and nerves from the lingual and the myloid branch of the inferior dental. Its excretory duct, named, from its discoverer, the duct of Wharton, terminates on the side of the frenum, in a narrow tuberculated orifice.

The sublingual gland is the smallest of the three. Parallel to that of the opposite side, it is separated from it by the base of the two genio-glossi, and rests on the mylohyoideus, which separates it from the intramaxillary. Occasionally, however, these two glands communicate by a slip from the intramaxillary below the muscle. It is supplied with blood by the sublingual, ranine, and submental arteries; and its nerves proceed from the lingual and hypoglossal. Its excretory ducts are manifold, and terminate either in several orifices on the sides of the frenum, or unite in a single tube, opening in the same region.

The use of these glands is to separate from the blood a watery but somewhat saline and sapid fluid, which has the twofold office of preserving the gustatory membrane in its necessary moisture, and of mixing with the food during mastication.

The saliva consists chiefly of water, holding in solution hydrochlorate of soda, sulpho-cyanic acid, and a minute portion of animal matter intermediate between albumen and osmazome. The presence of sulpho-cyanic acid, an active poison, is remarkable; nor is the purpose of such an agent known. From the saline matters in this fluid the tartar of the teeth is deposited; and occasionally minute concretions are formed in the glands or their ducts. That appearing in the ducts of the sublingual forms one variety of the affection named ranula.

CHAP. IIï. THE ORGANS OF VOICE.

Voice is of two kinds, according as it consists in the mere voluntary utterance of sound, or what is named, in reference to the animal world, cry, or in the utterance of certain peculiar modifications of this, denominated therefore articulate voice, or simply speech. Inarticulate voice is common to all the Mammalia and Birds. By the possession of articulate speech, however, man (μεξοdj) is particularly distinguished from the animal world in general.

These two forms of voice have two distinct organs. For inarticulate voice the larynx is placed at the superior extremity of the windpipe; and for that of speech, to the larynx are superadded the articulating powers of the teeth, lips, and tongue.

The larynx is a tubular organ, consisting of cartilages invested by membranes, connected by ligaments, and moved by muscles.

The cartilages are five in number, the thyroid, cricod, two arytenoid, and the epiglottis.

The thyroid cartilage, which forms the anterior and lateral region, consists of two lateral halves united on the mesial plane, where they form an acute salient angle, distinct beneath the integuments, and forming what is named dnepomum Adami. The anterior surface is slightly concave, covered by the thyrohyoideus, w ∖ Aλ an oblique line, to which the muscle now mentioned, the sterno-thyroideus, and inferior constrictor, are attached, and a posterior space covered by the two latter muscles. The posterior surface of the thyroid has in the middle a re-entrant angle, to which are attached the ligaments of theøŵtós and the thyro-arytaenoidei; on the sides two plane surfaces, corresponding above to the cellular tissue of the thyro-arytaenoidei, and below to the lateral crìco-arytaenoidei, and some fibres of the cricothyroidei attached to this part.

Each lateral half is quadrilateral and quadrangular. To the upper margin, which is obliquely sinuated like an f the thyro-hyoid membrane is attached. To the lower, which though shorter is also sinuated, the cricothyröid membrane and the cricothyroidei are attached.

The posterior margins, which are oblique and give attachment to several fibres of the stylo-pharyngei and par lato-pharyngei, terminate above in an elevated pointed process incurvated inwards and forwards, connected by a ligament to the hyoid bone, and below in a similar process, shorter however and triangular in shape, and articulated by its tip with the lateral process of the cricod cartilage.

The cricod or annular cartilage (κg∕κo^, annulus), which occupies the lower part of the larynx, is a complete ring of cartilage, narrow before, and broad and elevated behind, where chiefly it constitutes the laryngeal cavity. Convex in the middle, where it is subcutaneous, it widens laterally where the cricothyroidei are attached; and farther back, where it is covered by the thyroid cartilage, it presents the lateral process covered by synovial membrane for articulation with the triangular process of the thyroid. Its posterior region is broad and quadrilateral, with a ridge on the median line covered by the pharyngeal membrane only, and two depressions on each side, to which the posterior cricoarytaenoidei are attached. The inner surface, which is concave, narrow before and broad behind, is covered by the laryngeal mucous membrane. .

The superior margin presents before a large notch, to which the cricothyroid membrane is fixed, laterally the insertion of the lateral cricoarytaenoidei, and behind two convex surfaces, oblique in direction, covered by synovial membrane for articulation with the arytenoid cartilages, and between which this margin is covered by the arytenoid muscle. The lower margin, less irregular, descending before, sinuated on the sides and notched behind, is united by a fibro-mucous membrane to the firstring of the windpipe.

The arytenoid cartilages are two small bodies, triangular and pyramidal in shape, placed at the posterior part of the larynx, in the upper margin of the cricod cartilage. In each arytenoid cartilage may be recognised a concave anterior surface for the arytenoid gland, a concave posterior surface for the arytenoid muscle, an internal surface covered by laryngeal mucous membrane, a base concave and oval, covered by synovial membrane for articulation with the cricod, and a thin, convex summit, supporting a small cartilage (cornicula laryngis), invested by mucous membrane.

These bodies, which are named the tubercles of Santorini (capitula arytaenoidum) by whom they were discovered, are conical in shape, with a concave base for articulating with the summit of each arytenoid cartilage, and a pointed apex incurvated inwards and backwards. To their surface, with part of the arytenoid, the thyro-arytenoid ligament is fixed, and forms the beginning of the glottis.

These bodies partake of the general characters of cartilage, and are invested by perichondrium. The thyroid and cricod have a great tendency to ossification; and it is rare to find them unossified in advanced life.

The epiglottis is a thin slip of fibro-cartilage, of a paraboloid shape, covered by mucous membrane, attached at its base by cellular tissue to the inner surface of the hyoid bone and the upper margin of the thyroid cartilage, and by duplicatures of mucous membrane to the summits of the arytenoid cartilages. In this duplicature, on each side, is suspended a minute wedge-like cartilaginous tubercle, with the base upward, named the cuneiform.

These cartilages are articulated so as to admit of motion[7:2:806] at the points already indicated. The articulations are secured by ligamentous capsules; but the most important ligament is the thyro-arytenoid, which passes from the base of each arytenoid cartilage to the re-entrant angle of the thyroid, where the fibres are mutually mixed with that of the opposite side. The thyroid moves on the cricod, which may be regarded as the base of the organ; and the two arytenoid move on the upper margin of the cricod. The epiglottis is depressed over the laryngeal opening by the motion of the tongue in deglutition.

The agents of motion in the larynx are of two kinds; L·?, those which move the whole organ in relation to the neighbouring parts; and, 2dly, those which move the component parts of the larynx in relation to each other. To the former class belong the sterno-thyroid, thyro-hyoid, and inferior constrictor muscles, with those attached to the hyoid bone, the elevation and depression of which the larynx follows. The second comprehends the cricohyroid, the posterior cricoarytenoid, the lateral cricorytenoid, the thyro-arytenoid, and the arytenoid. The connections and relations of these muscles it is superfluous to detail more minutely than may be understood from the description already given of the cartilages. It is sufficient to say, that while the cricothyroid causes the thyroid cartilage to perform a swinging motion on the cricod, the posterior cricoarytenoid draws the arytenoid cartilages back, the thyro-arytenoid draws them forwards, the lateral cricoarytenoid separates them from each other, and the arytenoid, sometimes distinguished into transverse and oblique arytenoid muscles, approximates these cartilages in different degrees, according to the act in which they are used.

The several parts now mentioned are invested on the inside by mucous membrane, continuous above with that of the pharynx and tongue, and below with that of the trachea. Proceeding from the former boundary, it may be traced over the epiglottis and its gland, on the mesial plane and the thyro-arytaenoidei, and on the sides from the inner surface of the thyroid cartilage before to the outer margin and base of the arytenoid cartilages behind. At this part it rises to form two folds with rounded margins, extending from before backwards, and forming on the outsides a cavity with the arytenoid cartilage. These folds, though occasionally named the superior ligaments of the glottis, are truly mucous membrane doubled, with interposed filamentous tissue. They form an intermediate triangular space, with the base before and the apex behind. The inner surface of this membrane, directed to that of the opposite side, is concave, and forms a sort of pouch called the ventricles of the larynx (sacculi laryngis). The membrane here covers the thyro-arytenoid ligaments, over which it is tensely stretched, so as to form inferior folds, much tenser and firmer than the superior ones. These lower folds, which form a triangular interval with the base behind and the apex before, are the proper ligaments of the larynx, or vocal chords (chordae vocales) ; and the intermediate fissure is named the glottis, or rima glottidis. Though this opening is triangular in the dead body, its shape varies much in the living. By the joint action of the posterior cricoarytaenoidei and the arytaenoidei transversi, the thyro-arytenoid ligaments maybe rendered tense, the arytenoid cartilages approximated, and the fissure of the glottis become a mere slit.

Though it is impossible to adopt all the views of Do-dart regarding the powers of the thyro-arytenoid ligaments, it is certain that their tension and relaxation, with the mutual approximation of the arytenoid cartilages, are the essential agents of voice. Without the air passing through the glottis there is no voice. The glottis is also the organ by which the quantity of air admitted into the trachea is regulated. By means of its muscles it may be shut, and the breath retained, so as to fix the chest during any great effort. By contracting it, also, during coughing or forcible expiration, the air is forcibly expelled from the lungs, and necessarily carries at the same time foreign bodies.

At the base of the epiglottis, in the angle between it and the thyroid, the laryngeal membrane presents several orifices, which may be traced to a cluster of follicles imbedded in the submucous tissue at this part. This cluster has been named the epiglottic gland.

A similar glandular body, in the anterior depression of each arytenoid cartilage, is named the arytenoid glands.

Of the body named thyroid gland, situate on the sides of the upper end of the trachea, and generally referred to the appendages of the larynx, nothing is known. With the larynx it has certainly no relation.

The blood-vessels of the larynx are the superior thyroid or laryngeal, the first branch of the external carotid, and the inferior laryngeal branch of the inferior thyroid, the second branch of the subclavian artery.

The nerves are derived from the pneumogastric or nervus vagus, and may be referred to three divisions; the internal laryngeal, distributed to the proper muscles of the larynx; the external laryngeal, distributed to the thyro-pha-ryngeus, the sterno-thyroid, hyothyroid, and crieo-thyroid; and the recurrent, distributed to the laryngeal membrane, the thyro-arytenoid, and posterior crieo-thyroid muscles. The division of these nerves, or of the pneumogastric, from which they proceed, is followed by palsy of the muscles, and inability to open the glottis at will, or retain it open; and the result is dyspnoea, terminating in asphyxia

CHAP. IV. THE NERVOUS SYSTEM.

The nervous system includes two general divisions, a central and a distributed. The first is collected in a single and indivisible mass, contained in the cavities of the cranium and vertebral column, and may be designated by the general appellation of brain (cerebrum). The second consists of long chords connected with some part of the central portion and with each other, and distributed in every direction through the body in the mode of ramification. These are distinguished by the name of nervous chords or nerves (nervi).

SECT. I. THE BRAIN AND ITS MEMBRANES.

§ 1. the brain. Plate XXX.

The brain may be considered as a continuous organ, consisting of three divisions ;—the convoluted, the laminated, and the smooth or funicular portions. Of these divisions, which are framed according to the peculiar external configuration of each, the first part corresponds to what is called the brain proper (cerebrum) ; the second to the small brain (cerebellum) ; and the third to the oblong body contained in the vertebral column, and known under the name of spinal chord.

The convoluted portion presents two surfaces, an outer or convoluted, and an inner or figurate. The laminated portion in like manner presents two surfaces, an outer or laminated, and an inner or central. The third has only one exterior surface.

The shape of the first two divisions is like that of the cranial cavity in which they are contained, oblong spheroidal or ovoidal, with the small extremity of the ovoid before, and the large one behind.

The human brain is larger and heavier in proportion than that of any other animal. The three parts, the brain, cerebellum, and spinal chord, after being washed and [7:2:807]emptied of blood, weigh in the adult from two pounds five ounces to three pounds three ounces, and at an average about three pounds; and of this the brain alone weighs two pounds. The statement of Haller, that the brain weighs five pounds, is incredible, unless it be understood of Troy weight, in which ease even it seems exaggerated, since of more than 200 brains weighed by Soemmering, not one amounted to four pounds. The statement, that the brain of Cromwell weighed six pounds and one fourth, seems equally incredible. The specific gravity of the adult brain is to water as 1031 to 1000. This, however, varies with age. The cerebellum weighs about five or six ounces, and is therefore about the seventh part only of the weight of the brain.

The brain (cerebrum) is divided above and before into two lateral halves, named hemispheres (hemisphaeria), right and left, separated by a deep furrow, in which the vertical, crescentic, or dichotomous portion (falx) of the hard membrane is received. Each hemisphere is bounded by a superior or convex, an inner or plane, and an inferior convex and concave surface. The lower surface of each hemisphere, also, anatomists distinguish into three lobes, an anterior, posterior, and middle.

The cerebellum is also divided into two hemispheres, separated by a middle furrow of less depth, receiving, as that of the brain, acrescentic production, smaller in size, from the hard membrane.

The exterior surface of the convoluted division is formed into eminences longitudinal and rounded, but directed in various ways, named convolutions or circumvolutions (gyri, Soemmering, WenzeD, and separated from each other by deep hollows (sulci). To see this surface, which is termed the convoluted, the vascular membrane termed pia mater (meninx tenuis) must be removed.

The convoluted surface of each hemisphere may be divided into five regions: 1. The commutual or dichotomous; 2. the lateral-superior or convex; 3. the anteroinferior or frontal; 4. the medio-inferior or spheno-temporal; and 5. the posterior or cerebellie region.

1. The commutual, plane, of a shape nearly semicircular, forms the mesial boundary of each hemisphere, and corresponds to the falciform or dichotomous portion of the hard membrane (μηνrfζ, δκ,ληξα, meninx dura), by which it is separated from the similar surface of the opposite hemisphere. Before and behind it extends from the superior to the inferior surface of the brain; but a considerable portion of its middle is terminated by the upper surface of the middle band (mesolobe, corpus callosum), which lies between the two hemispheres. It is contained between the semicircular and the rectilinear margins.

2. The convex region occupies the anterior, upper, lateral, and posterior parts of the hemisphere, from their anterior to their posterior extremity, and from the semicircular margin to a line which extends between these extremities along the lateral borders of the organ.

3. The antero-inferior or frontal rests on the horizontal part of the frontal and ethmoid bones, commencing before with a curved outline, bounded behind by the curvilinear hollow named the fissure of Sylvius, and at its inner or mesial margin by the great fissure which separates the hemispheres. This inner margin presents one convolution, consisting of a longitudinal eminence, extending in the adult brain about 1-1/2 inch from the posterior towards the anterior end of the ñotch. The outer furrow contains the cerebral portion of the first pair or olfacient nerves. (1,1.)

4. The medio-inferior or splιeno-temporal is situate immediately behind this region, from which it is separated by the curvilinear hollow (fossa Sylvii). In the ordinary descriptions this forms the middle lobe; while the posterior part, corresponding to the cerebellum, though distinguished by no evident limit, is with equal impropriety named the posterior lobe. The whole region, from the curvilinear hollow to the posterior tip of the hemisphere, may, however, be subdivided into two, the medio-inferior and postero-inferior regions of the convoluted surface, according as they correspond to different containing parts.

5. The posterior cerebellie region of the convoluted surface, which is plane, corresponds to the horizontal or cerebellic part of the hard membrane.

The convoluted surface is formed of cerebral matter, of a gray or dirty wax colour, the surface of which is smooth and polished where it has not been rent by the removal of the membranes and their attachments. In the furrows are many minute orifices, into which the soft membrane (λε∙τn; μψ∕yξ, meninx tenuis, pia mater) transmits filamentous bodies, containing minute blood-vessels.

Neither the eminences nor the hollows are uniform in number or distribution; and in no two brains is it possible to trace any similarity in their figure, presence, or direction, in the upper, lateral, and posterior part of the convoluted surface, unless where it approaches the central or figurate surface, where a number of important objects are presented.

The convoluted surface communicates with another interior surface at two parts; L·/, on the middle plane, under the posterior end of the middle band or mesolobe (corpus callosum) ; 2d , on each side of the middle plane, at the outer margin of the fluted masses termed limbs of the brain (crura cerebri), between these limbs and the posterior end of the optic chamber or couch (thalamus opticus). This surface of the organ may be termed the central or figurate.

The exterior surface of the cerebellum consists of thin portions of cerebral substance named plates (larninae), or leaves (folia), placed contiguously, either parallel or concentric, and separated by furrows of various depth. This surface, which may be named the laminar or foliated surface of the small brain, communicates also with the figurate surface,—L·/, above on the middle plane, between the semilunar notch behind, and the white cerebral plate termed Vieussenian valve before; 2d , at its inferior surface, between the almonds or spinal lobules above, and the upper end (medulla oblongata) of the spinal chord below.

The outline of each hemispherical surface of the cerebellum describes three fourths of a circle; and as the segments mutually meet towards the mesial plane, the mode of union varies according to the figure of the objects to which they are adapted. Is/, The hemispherical border, approaching the anterior part of the organ, is suddenly interrupted where the cerebellie peduncles (crura cerebelli) are connected with the protuberance; and, pursuing a retrograde direction on each side towards the mesial plane, forms a re-entrant curvature or notch—the semilunar — S corresponding to the lower pair of the bigeminous bodies.« 2d , The hemispherical borders, approaching the posterior part of the cerebellum, proceed, near the mesial plane, by an acute circular turn, almost straight backwards, and form, at the posterior edge of the organ, a deep rectangular notch, H, not unlike the figure of the ancient lyre, named the perpendicular fissure of Malacarne, or the purse-like fissure of Reil, and containing the cerebellie vertical portion of the hard membrane (falx cerebelli). Between these two boundaries the cerebellie plates, of which the hemispheres consist, are united in the middle by an interlacement, named suture (raphe), of the cerebellum. A large hollow between the hemispheres, extending backwards from the semilunar to the purse-like fissure, is the small valley (vallecula) of Haller.
[7:2:808]

Each hemispherical surface consists of five lobes; 1. the anterior-upper or quadrilateral; 2. the posteriorupper; 3. the posterior-lower; 4. the slender , s rarely exceeding three lines in breadth; 5. the two-bellied or biventral; and 6. the central lobe. The first two belong to the upper or flat hemispherical surface; the next three to the lower or convex hemispherical surface; and the sixth, common to the two hemispheres, is situate on the mesial plane of the upper surface, between the anterior end of the middle line (raphe) and the middle or apex of the semilunar fissure.

The biventral lobe is pointed, and its margin concave; and between this margin and the parts of which the valley consists is placed a group of plates, convex and rounded, named the tonsil or tonsils (tonsilloe; amygdalae; the spinal lobule of Gordon).

In the angular hollow between the biventral lobe and the peduncle (crus) of the small brain, is the flock, a minute body, of irregular shape. Each flock consists of six or seven plates (laminoe), starting directly from the beginning of the peduncle, and with the concave margins directed towards the protuberance.

The valley is distinguished into three bodies, the pyramid, uvula, and nodulus. The first is a group of 20 parallel plates, with a triangular apex, bounded behind by the purse-shaped notch, and before by another cluster of plates called the uvula. The uvula, which is anterior, consists of twelve laminated leaves, is six lines long and four broad, and is smaller than the pyramid, and conical, with its base turned to that body. Lastly, anterior to the uvula, and separated from it by a furrow, is the laminar tubercle (tuberculo laminoso) or nodule, consisting of about ten thin transverse plates, the smallest in the row.

The second surface of the brain, in situation interior or central, may be named the figurate or symmetrical. Instead of presenting the uniform eminences and hollows which distinguish the convoluted surface, it is moulded into definite shapes, which correspond with each other, as they are situate on opposite sides of the middle plane,— or the parts of which, when situate on this plane, are exactly symmetrical. The surface formed by these figured objects bounds what are termed the ventricles or cavities of the brain. They cannot justly be termed cavities any more than the hollows between the convolutions, but ought to be viewed as continuations of the exterior or convoluted surface.

The central or figurate surface of the brain presents the following objects. The central band, beam, or mesolobe, a mass of white cerebral matter, uniting both hemispheres on the mesial plane, with the twainband or vault below; the hippocampus major on each side; the anterior pyriform eminence or striated body on each side; the posterior pyriform eminence or optic chamber on each side; the semicircular band on each side; the ergot on each side; the conarium on the mesial plane; the bigeminous eminences on the mesial plane; the valve on the mesial plane; and its pillars on each side.

The commutual or dichotomous region of the convoluted surface is terminated below by the upper surface of a white band uniting the two hemispheres. This, which was named by the ancient anatomists the smooth or polished body (<swμa nλλοuδsς, corpus loeve), to distinguish it from surfaces formed by a cutting instrument, appears in the form of white fibrous matter, passing transversely between the hemispheres, and marked by three longitudinal lines, one on the mesial plane, and one on each side. This is the middle or central band (mesolobe of Chaussier). Near its middle is a bundle of gray lines, which may be traced to the central portion of the hippocampus major.

The posterior extremity of this body is rounded, and communicates with the chamber named third or middle ventricle. This surface is continued forward, and forms the vault or cieling (fornix, Die Zwillingsbinde, the twainband, ReiD. The names of callous body and vault are used, as if they were denominations of different bodies. If they are still retained, it ought to be stated that they are names applied to opposite surfaces of the same object.

The relations of the posterior end of the middle band are as follow. The handle of a scalpel inserted beneath it is found to be in the middle ventricle, with the vault above, the conarium or pineal body, and four eminences of the upper surface of the protuberance (corpora bigβ- mina) below, and a part of each optic chamber on each side. The vault or inferior surface of the band has the shape of an isosceles triangle, with the base behind. Before it is incurvated downward as it becomes narrow; and the space between the band and it is occupied by a thin double plate of cerebral matter, separating the two ventricles, and named the diaphanous partition (septum lucidum). (s, s, s.) The fornix terminates before, in two bodies named anterior pillars. (Fig. 3, f, f.)

The posterior end of the middle band penetrates into the substance of the hemispheres; but the gray chords already noticed, pursuing their lateral course, are immediately enveloped in white plates derived from the sides of the vault, and assuming a cylindrical appearance, form, opposite the cerebral limbs, a body with a free rounded surface, which bends in a curvilinear direction laterally and downwards, and is the great hippocampus or cylindroid process. (Chaussier.) In observing this curvilinear course, it rests on and corresponds, but without adhesion, to the upper margin of the cerebral limb as it issues from the optic chamber; and the surfaces of both parts, though kept in apposition by vascular membrane, are free and unadherent. It forms the great cerebral fissure of Bichat.

The hippocampus, therefore, consists of two parts. The first, which is the gray indented band (le corps godronnée, Vicq-d’Azyr), is an inner or central portion, as thick as a large crow-quill, gray in colour, indented at the free edge, adhering to the cerebral substance by its opposite margin, and connected with the upper surface of the central band. The outer or second part, which is a broad thin plate of white cerebral matter folded over the gray indented band, as a map is rolled over a cylinder of wood, known under the name of the tape or fringe of the hippocampus, is connected with the lower surface of the same central band, or the vault (fornix) of the brain.

At the inferior region the communication is effected by the curvilinear hollow. (Fig. 1, s, s.) This presents, 1st, cerebral substance, penetrated by numerous holes of various size, named the white perforated substance (lamina perforata) ; 2dly, the unconvoluted space; 3dly, the long cerebral band termed the optic tract ; and, 4thly, the limb of the brain. This body, with that of the opposite side, is covered by a portion of the convoluted surface, the inner and prominent surface of the medio-inferior or spheno-temporal region.

The convoluted surface, which covers the anterior end and outer margin of the cerebral limb, when everted, presents the thin white body named the tape or fringe (taenia) of the hippocampus; and if the portion of convoluted brain next the curvilinear hollow be raised and everted in the same manner, the anterior end of this object, termed the foot (pes hippocampi), comes into view. The fringe of the hippocampus forms, in the natural position of the organ, the outer and lower border of the opening; while the limb of the brain, and the outer [7:2:809] and lower surface of the optic chamber, form its inner border.

When the central surface is exposed by removing the central band and the vault and
cieling
of the ventricles, two pyriform eminences, an anterior and posterior, come into view. The anterior is ash-coloured or gray, inclining to wood-brown, with the round convex extremity before, and the small end tapering backwards and outwards, so as to inclose the round end of the posterior eminence. The surface is smooth and convex, consisting of a thin covering of gray cerebral matter. The interior consists of an admixture of white and gray, so as to form alternate streaks,—a circumstance from which these eminences on each side have been named the striated bodies (corpora striata). At their anterior mesial extremity are two rounded vertical bodies of white cerebral matter, descending from the anterior end of the vault. These are the anterior pillars, which are thus interposed between the interior front of the striated bodies.

The posterior and internal margin of the striated bodies is bounded by a gray, hard eminence, about a line broad, stretching with a sinuous or winding direction from its mesial and anterior to its external lateral and posterior margin. This is the semicircular fillet or band (taenia semicircularis, centrum semicirculare geminum). Always firmer than the neighbouring parts, it appears to be the external margin of a gray-coloured stratum or wall of cerebral matter between the anterior and posterior pyriform bodies.

Connected before and on the outside to the striated body by means of the double semicircular chord (centrum semicirculare geminum, Vieussens), each optic eminence presents four free surfaces—the upper, the inner, the posterior, and the lower. The upper is gently rounded, convex, and white in colour; its limits are not easily defined. The outer margin is bounded by the circular band, which even passes anterior to it, so as to form its boundary in that direction also. Behind, it is less distinctly limited, unless by the appearance of a considerable prominence, named the posterior tubercle of the optic couch.

The inner margin of the upper surface is distinctly marked by a small, sharp, gray line, which, beginning insensibly at the anterior part of the body, becomes more distinct as it extends backwards, and ultimately bends towards the median plane. There it unites with a similar elevated line of the opposite optic eminence; and to the point of union is attached a small conical body with a minute point, of a gray colour, and of a shape like that of the pine-apple. This is the pineal gland (glandula pinealis, conarium) ; and the minute linear eminences which form the inner edge of the upper optic surface have been named peduncles of the pineal gland.

The inner surface of the optic couch or chamber presents the small portion of soft cerebral matter (commissura mollis) which unites it to the similar surface of the opposite body; and the intermediate space between the inner surfaces of these bodies on each side constitutes the third or middle ventricle (ventriculus tertius). Its posterior edge, however, is terminated by the cerebral limb of that side; and the lower edge meets that of the opposite one, and is connected to it by a portion of brain which forms the lower part of the middle ventricle, and corresponds on the outside to the bridge of Tarin (pons Tαrini). : The posterior surface of the optic chamber is convex and continuous with the unconvoluted space. Its most convex part presents two oblong roundish eminences, separated by a linear depression, which may be traced downwards with an outward curvature, and forwards about five or six lines, in a broad white band, crossing two fluted masses mutually converging behind at an angle. These eminences are the geniculate bodies (corpus geniculatum externum et internum), the outer the largest of the two (fig. 1, g, g); the white bands are the optic tracts or origins of the optic nerve, issuing from the geniculate tubercles (o, t); and the fluted converging masses are the limbs of the brain (crura cerebri).

On the inner or mesial side of the geniculate bodies, and separated only by a lineaι∙ furrow, are the bigemi-nous eminences, four orbicular elevations, two above and two below; two on each side of the mesial plane, with an intermediate cruciform furrow. By the ancients, who examined chiefly brute animals, the superior and larger pair were named nates (yaovro∕), the inferior testes (δίδυμοι). These eminences occupy the upper surface of the protuberance, and partly that of the limbs of the brain; and while the eminences are situate between the posterior ends of the optic chambers above, the limbs appear to issue from the centre of these chambers below, and the linear furrow marks the point of junction.

These bigeminal eminences, however, though occupying the superior surface of the protuberance, adhere not everywhere to its substance. (Fig. 3.) The mesial furrow is formed on the upper surface of a thin plate of white cerebral matter, which extends from the level of the pineal peduncles above, to the upper margin of the cerebellum below, like a veil, and is named the cerebral valve (valvula Vieussenii). The lower surface of this is free for about two or three lines broad; and, though applied to a similar surface on the mesial line of the upper region of the protuberance, does not adhere, but forms a canal with the third ventricle above and the fourth below, named the aqueduct of Sylvius (iter a tertio ad quartum ventriculum) (i). While the outer halves, therefore, of the eminences adhere to the matter of the protuberance, the inner are attached to that of the valve, (n, t.)

The lower or cerebellic margin of the valve is free, and overhangs as it were the fourth or ccrebellic ventricle. On each side, however, is a longitudinal rounded body of white matter, which passes from the lower pair of bigeminous eminences (testes) to the cerebellum. These are named the pillars of the valve (columnae valvulae Vieus-senii, processus a cerebello ad testes). The fourth or pathetic nerve (trochlearis) rises partly from the valve, partly from its lateral pillars, and is seen issuing on the sides of the protuberance not larger than a thread.

The lower surface of the optic chambers presents within the convoluted space the limbs of the brain (crura cerebri), two fluted semicylindrical masses, converging backwards, and inclosing by their junction a triangular space, with the apex behind—the intercrural hollow. The inner margin of the limbs presents the origin of the third or oculo-muscular nerves (oculo-motorii) ; about half an inch anterior on the intercrural hollow are the lenticular or pisiform bodies (tubera, v. corpora candicantia), two hemispherical tubercles of white matter; and immediately anterior is the hypophysis or pituitary gland, a broad quadrilateral reddish-gray prominence, with the anterior margin rounded, the posterior concave, inclosed before and on the sides by the converging optic tracts and commissure, (p ∙)

The limbs are obliquely crossed at their outer anterior end by the broad part of the optic tracts as they descend from the geniculate bodies. Their posterior convergent extremities are lost in the substance of the annular protuberance (pons Varolii, nodus cerebri), a convex rounded white body, with transverse fasciculi separated by linear furrows, (n.) Connected before with the crura or limbs, from which it is separated by transverse sinuous furrows, it is connected on the sides with the cerebellum by short semicylindrical stalks or peduncles (crura cerebelli), and [7:2:810]behind with the beginning of the spinal chord (medulla oblongata). It is marked on the middle by a longitudinal furrow, in which is placed the basilar artery, the united trunk of the vertebrals. Its convexity corresponds to the concavity of the basilar groove of the occipital bone, on which it rests. This eminence may be regarded as the general central point of the cerebral nervous system, with which all the other parts are connected,—with the cerebral hemispheres by the crura cerebri, with the cerebellic hemispheres by the crura cerebelli, with the upper internal part of the optic chambers by the bigeminous eminences, and with the spinal chord by the medulla oblongata. From its anterior lateral margin the tergeminal or fifth nerve arises; from the posterior furrow the abducent or sixth nerve; and from the upper anterior margin of the cerebellic peduncle the eighth or lateral facial.

Continuous with and behind the protuberance is the beginning or bulb of the spinal chord, a part distinguished on the ground of an obsolete hypothesis by the name of medulla oblongata. Thick and prominent, its surface is moulded into six oblong-ovoidal eminences, three on each side of the mesial plane; the pyriform or pyramidal eminences before, the restiform bodies behind, and the olivary eminences on each side.

The pyriform eminences (corpora pyramidalia) are two oblong-oval bodies, broad above, tapering below, separated by a mesial line, and bounded laterally by a furrow separating them from the olivary bodies, occupying the anterior-inferior part of the bulb of the chord, and resting on the lower third of the basilar groove. The mesial line terminates above in the foramen caecum of the posterior furrow of the protuberance, (p.)

The olivary (corpora ovata), placed on the outside of the pyramidal bodies, occupying partly the front, partly the side of the bulb, give it a lateral and transverse projection. In the intermediate furrow are the initial filaments of the hypoglossal or middle lingual nerve; and in the external furrow and sides those of the glosso-pharyngeal and pneumogastric nerves, (o, o. )

The posterior-upper part of the medulla oblongata consists of two longitudinal cylindrical bodies, stretching between the cerebellic peduncles above and the spinal chord below. These are the chordal processes of Ridley, the restiform or rope-like processes of Morgagni, the pyramidal bodies of Haller, Malacarne, and Reil, and the posterior pyramidal bodies of Ruysch, Prochaska, and Soemmering. Above, where they are connected with the cerebellic peduncles, they are separated by a triangular space with the apex downward, but below by a deep furrow, the calamus scriptorius of the ancients, at the bottom of which, when separated, may be observed white chords proceeding from the process of one side, plaited with those of the other. These decussating fibres, which are confined entirely to the mesial margin of the restiform processes, are believed to establish a crossing connection between the right and left sides of the peduncles and the protuberance. The intermediate cavity is named the fourth ventricle. From the inner surface of the restiform process issue several of the initial filaments of the seventh or auditory nerve.

The spinal chord or funicular brain is a cylindrical body occupying the interior of the vertebral canal, from the margin of the occipital hole to the first lumbar vertebra ; large and round on the cervical region, broad on the dorsal, and terminating in a brush-like expansion, denominated the cauda equina. On its dorsal surface may be seen a slightly depressed line continued from the middle furrow of the restiform bodies, but becoming faint and indistinct in the region of the back.

The central or figurate surface is smooth, polished, and possesses a degree of closeness of texture which prevents it from being readily abraded. These qualities are ascribed by Reil to a thin pellicle, which he terms epithelia. Though there is no proof of the existence of the covering, the term may be used to designate the smooth surface of the organ.

Of the central surface not only does every division mutually communicate, but the central surface of the convoluted communicates with that of the laminated part of the organ. The lateral divisions, named ventricles, communicate directly with each other below the vault, the surface of which lies over the thalami; both communicate with the third ventricle, which by the Sylvian aqueduct communicates with the fourth; and the posterior part of the lateral ventricle communicates with the digital cavity and inferior recess.

The central surface is covered by a vascular membrane (plexus choroides), continued from the pia mater of the convoluted surface.

Between the two surfaces now described is placed the proper matter of the brain, white and brown, which in different regions of the organ is differently arranged.

The convoluted surface consists of a stratum of gray cerebral matter, arranged in the granular form. When indurated by immersion in alcohol or dilute nitric acid, it breaks with a small conchoidal fracture, occasionally uneven, and with an uneven granular surface, void of lustre and without fibrous arrangement. The only part of the convoluted surface presenting the latter appearance is the unciform band· uniting the anterior and posterior lobes. (Fig. 5, v.)

Within the convoluted surface is contained a large quantity of white matter, surrounding the figurate surface and its divisions. The section of this, usually named the oval centre of Vieussenius (centrum ovale), shows merely the extent which this occupies in the upper part of the brain, but communicates no information on the intimate structure of the organ.

In intimate organization the brain may be distinguished into four parts; W, the brain, containing the striated nucleus; 2d, the cerebellum, containing the. moriform body; 3d, the head or bulb of the chord, containing the moriform body; and, ⅛th, the annular protuberance as a central point of the whole.

The white fibrous matter of the central band, passing into the hemispheres on each side, diverges like the rods of a fan or the rays of a luminous body, and forms an arrangement denominated by Reil the radiating crown, and which may be regarded as the exterior investment of the striated nucleus, which constitutes the internal substance of the striated bodies and optic chambers. (Fig. 5, c.) The arrangement of white and gray matter in this part is so peculiar, that within the limits of this sketch it is impossible to convey a distinct idea of it. It may be stated in general that the fibrous matter of the limbs extends from the protuberance through the substance of the thalamus and part of the striated body; and while in this manner it maintains a connection between the protuberance and the brain above, by means of the cerebellic peduncles on the sides, and the head of the chord below, it communicates with the cerebellum and spinal chord behind and below. The moriform bodies (corpora dentata, corpora ciliata, corpora rhomboidea), which consist of white matter inclosed in a brown capsule, and the cerebellic and olivary eminences, are analogous to the striated nucleus of the brain; and the three may be regarded as the respective centres of each. The annular protuberance, consisting internally of transverse fibres closely interwoven with longitudinal ones, is the general or common centre of the three.
[7:2:811]

The substance of the funicular or vertebral portion con- • sists almost entirely of white fibrous matter, extending t longitudinally from the cranial to the sacral extremity, but bending off laterally at the origins of the spinal nerves in the form of arches.

. The brain is supplied with blood by the internal carotid arteries and the two vertebral arteries, derived from the subclavian. The former, entering the cranium by the carotic canals, sends a posterior communicating branch, inosculating with the principal division of the basilar, and an anterior communicating, which joins the vessel of the opposite side. By these communications, the branches of the basilar artery behind, and the carotids before, form an arterial hexagon round the sella Turcica, from which arise two anterior vessels (anteriores cerebri), distributed to the central band, and two lateral (rncdiae) or Sylvian arteries, distributed to the perforated spot, the Sylvian fissure and striated nucleus. The vertebral, entering’ by the occipital hole, send branches to the head of the spinal chord, and uniting to form the basilar, supply the protuberance and cerebellum; then divaricating into posterior cerebral, finally inosculate with the internal carotid to form the arterial hexagon as mentioned. The blood is returned by triangular canals named sinuses, of which there are the superior longitudinal, the inferior longitudinal, the cerebellic (torcular Herophili), the lateral, the circular, the superior petrous, the inferior petrous, and the cavernous. The four latter pairs are small sinuses opening into the lateral, where it emerges from the cranium by the temporo-occipital fissure (foramen lacerum in base cranii posterius).

§ 2. THE CEREBRAL INVESTMENTS OR MEMBRANES.

The brain is said to be surrounded by three membranous envelopes, the hard membrane (meninx dura, dura mater), the web-like membrane (tunica arachnoidea), and the soft or thin membrane (meninx tenuis, pia mater). To this arrangement, which has been adopted by almost all writers, there is perhaps no great objection. But it simplifies the subject, without misrepresenting, to refer them to two only; one of which, the hard membrane (meninx dura, μηvιγξ <rκλη^, dura mater), is common to the brain with the inner surface of the scull; the other, the thin membrane (nιeninx tenuis, μrinγζ λε~rη, pia mater), is proper to the brain only. They may be distinguished, therefore, by the terms common membrane of the brain and proper membrane of the brain. The arachnoid, again, is a pellucid web common to the cerebral membranes.

The first of these, the common or hard cerebral membrane (meninx dura, dura mater), presents two surfaces, an outer or cranial and an inner or cerebral. The outer surface is irregular, filamentous, and vascular, and the substance of which it consists is distinctly fibrous. The fibres, however, do not follow any uniform direction, but are interwoven irregularly. Maceration causes this membrane to swell and become separated into fibrous threads. It is liberally supplied with blood-vessels, by which it is connected to the inner surface of the scull. No nerves or absorbents have been discovered in it. This outer or cranial surface of the dura mater is of the nature of periosteum. Its vessels may be traced into the inner table; it contributes to the formation of the cranial bones in the foetus, and their nutrition during life.

The inner or cerebral surface of this membrane is smooth, polished, and shining; and, when examined in water, it appears to be formed by a very thin, transparent membrane, through which the cranial or outer surface and the fibrous structure of the hard membrane may be recognised. This pellucid inner membrane, generally termed the inner lamina, is the exterior division of the arachnoid membrane.

The dura mater is an extensive membrane, lining not only the interior surface of the scull, but, in a modified form, that of the whole vertebral column. The inner surface of each vertebra has a proper periosteum continuous with the periosteum of the outer surface; and from this issues a quantity of filamentous tissue, which penetrates directly a membranous canal, evidently of fibrous structure (theca vertebralis), tough and firm, but more delicate than the cranial dura mater. The dura mater in its course forms sundry prolongations; for instance, the large crescentic one named the falx, the horizontal one termed tentorium, and the small crescentic one named falx minor or cerebelli.

The thin, soft, or immediate and proper cerebral membrane (pia mater, meninx tenuis) presents in like manner two surfaces, a smooth or cranial, which is exterior, and a filamentous or cerebral, which is interior and central.

The outer or smooth surface of the thin membrane (pia mater) has a glistening appearance, and is formed by a very thin transparent membrane, exactly similar to that which forms the cerebral surface of the dura mater. This surface, named in the ordinary works the web-like membrane (tunica arachnoidea), is believed to be a separate membrane from the pia mater ; but that which forms the inner or cerebral surface of the dura mater has a claim equally strong to this distinction.

The inner or cerebral surface of the proper membrane is filamentous, flocculent, and sends out many angular filamentous processes, which, by numerous minute arteries and veins, communicate with the convoluted surface of the brain. These processes (tomenta) correspond to the furrows of the convoluted surface in which they are lodged. In detaching the membrane from this part of the brain, numerous vessels are drawn out of its substance; and when the membrane is injected these vessels may be seen distinctly filled, and communicating with the gray matter of the convoluted surface. The veins of this membrane may be traced to the sinuses. Neither nerves nor absorbents have yet been recognised in it. Bichat considers it to contain much cellular tissue, which, however, is denied by Gordon, who could not recognise it. The difference, however, consists merely in name. The pia mater, indeed, possesses no cellular tissue like the subcutaneous, the submucous, or the subserous. If, however, a portion of the arachnoid be peeled from it by careful management of the forceps and blowpipe, there is found a quantity of loose filamentous matter uniting this tissue to the fine web of the former. The existence of this tissue between the pia mater and arachnoid is further demonstrated by the phenomena of serous infiltration.

The pia mater, or proper membrane of the brain, consists of two parts, an outer, covering the convoluted surface of the brain, and an inner or central, entering the cavities formed by the inner, central, or figurate surface, and spread over this surface in the form of what has been termed the vascular or choroid web (plexus choroides; tela choroidea).

The continuity of the pia mater or exterior division of the proper cerebral membrane, with the choroid plexus or interior division, may be demonstrated in the following manner. First, The pia mater may be traced behind and below the posterior extremity of the middle band (ΰωμα. rιλλοn0ες, corpus callosum, der balken), where it is continuous with the transverse web called velum interpositum, and which may be regarded as the first part of the central division. Secondly, From the situation of the velum interpositum, it may be traced forwards on both sides of the [7:2:812]mesial plane into the lateral ventricles, spread over the surface of the optic thalamus and striated eminence in the form of the vascular web called choroid plexus, the right half of which communicates with the left by means of a similar slip of vascular membrane lying beneath the vault (fornix), and behind the anterior pillars of that body at the spot termed foramen Monroianum. Thirdly, It may be traced over the geniculate bodies and thalami into the posterior-inferior cornu, or sinuosity of the lateral ventricle, where it covers the great hippocampus. Fourthly, It may be traced at the angle between the cerebellum and medulla oblongata, or what is named the bottom of the fourth ventricle, where it forms a very minute choroid plexus, seldom noticed by anatomists, but not less distinct, and which may be traced up the fourth ventricle to be connected with the velum interpositum, in the middle ventricle, and with the lateral portions of the hippocampus on each side. Each of the divisions of the choroid plexus now enumerated may be shown to be mutually connected, and to form parts of one general membrane, which again constitutes the inner or central division of the membrane of which the pia mater forms the exterior. Each division of the choroid plexus, in like manner, is connected, by means of minute blood-vessels, to the portion of the figurate cerebral surface on which it rests; and it appears to sustain vessels as the pia mater does to the convoluted surface.

In clear water the choroid plexus may be spread out, like the pia mater, in the shape of a thin semitransparent web, one surface of which is smooth, the other somewhat flocculent, and the substance of which is traversed by numerous minute vessels. The transparent web, which forms the basis of this membrane, is filamento-vascular; and its smooth free surface, a continuation of the arachnoid membrane, is smooth, polished, and thin, like silver paper.

The arachnoid membrane is common to the dura mater, pia mater, and choroid plexus. It covers the inner surface of the first membrane, to which it communicates its shining polished appearance, though the want of subjacent filamentous tissue causes it to adhere so firmly, that it cannot be readily demonstrated. After covering the free surface of the pia mater, it follows the course of that membrane into the central surface of the brain, and covers the upper or unadherent surface of the several divisions of the choroid plexus. For the demonstration of this fact we must be permitted to refer to Dr Craigic’s Elements of General Anatomy (chap, xxiii. sect. 1), where the reader will find proofs, which the limits of this sketch do not allow us to adduce here.

From these it results that the arachnoid membrane possesses in arrangement and distribution a great resemblance to the serous membranes. It differs, nevertheless, in its extreme tenuity, in the closeness with which it adheres to the collateral tissues, and in its slight disposition to albuminous exudation. It appears to contain in its structure less filamentous tissue than the pure serous membranes.

The brain is developed from the branches of the internal carotid and vertebral arteries ramified through the vascular membrane (pia mater). Formation commences in two orders of vessels mutually directed to each other,—those of the convoluted surface (pia mater), and those of the central (plexus choroides). The central substance of each part is first deposited; and from these points deposition and moulding proceed to the two circumferences of the organ. The surfaces are therefore formed last; and the vessels gradually shrink as the process approaches to completion.

SECT. II. THE DISTRIBUTED CHORDS; THE NERVES.

The nerves may be distinguished into classes according to the parts of the brain with which their cerebral ends are connected. On this principle they may be arranged in the following order.
[table]

The spinal nerves are derived from anterior and posterior roots separated by the ligamentum denticulatum, a fibrous notched ligament, covered by arachnoid membrane. According to the researches of Charles Bell and Magendie, the anterior roots furnish motive filaments, and the posterior sensitive. The central connections of most of these nerves have been already mentioned; and their distributed connections have been, and will continue to be, incidentally noticed under the heads of the several organs. It is requisite, however, to notice shortly the relations and general distribution of several nervous chords which perform an important part in the functions of the animal body. These arc the pneumogastric, the phrenic, and the great sympathetic or intercostal nerves.

The pneumogastric or nervus vagus, the 8th pair of the old nomenclature, the 10th in correct enumeration of the cerebral nerves, rising by various filaments from the furrow between the olivary bodies and the restiform, and from the posterior upper surface of the latter, emerges from the cranium with the jugular vein by the temporo-occipital hole. Here, closely united by filamentous tissue to the hypoglossal, spinal, and glosso-pharyngeal, it descends before the rectus anticus and longus colli on the outside of the carotid artery, though in the sheath with it, and before the subclavian artery on the right side, on the left before the carotid, enters the chest, where it enlarges in size considerably. (Plate XXXI. v, v.) In the chest it passes behind the bronchi in the posterior fold of the pleura, and is closely connected to the oesophagus in the shape of a thin cord. Both trunks, on reaching the cardiac end of this tube, pass with it through the diaphragmatic aperture, and are distributed to the stomach. In this course the pneumogastric nerve is divided into five orders of filaments.

1. In the neck it gives branches to the pharynx, and, communicating with the glosso-pharyngeal, forms the pharyngeal plexus, and furnishes a superior laryngeal branch, an external laryngeal, and an internal laryngeal, the latter chiefly to the intrinsic muscles of the larynx.

2. In the chest it sends off branches, which, communicating with those of the superior cervical ganglion, are distributed to the heart.

3. In the chest also it gives off the inferior laryngeal or recurrent nerve (r), which on the right side winding round the subclavian, on the left the arch of the aorta, re-asccnds in the lateral furrow between the windpipe and oesophagus, and giving off cardiac, pulmonary, oesophageal, thyroid, and tracheal filaments, is finally distributed to the intrinsic muscles of the laryngeal cartilages. These multiplied connections tend to associate the motions of the glottis with the lungs, and to maintain a general consent between the nharvnx. larvnx. oesoŋhauus, trachea, lungs, and heart.
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4. The pneumogastric trunk forms with the filaments of the inferior cervical ganglion the anterior pulmonary plexus, and alone it forms the posterior pulmonary plexus, which sends filaments to the lower part of the windpipe, the bronchi, the pulmonary artery and veins, and the oesophagus.

5. After passing the diaphragmatic aperture, the right pneumogastric trunk forms at the cardiac orifice of the stomach a plexus, from which filaments proceed to the pylorus, the gastro-hepatic artery, the right coeliac ganglion, the duodenum, the pancreas, the gall-bladder, and the liver, where it communicates freely with the coeliac ganglions. The pneumogastric of the left side is distributed chiefly to the pylorus and its arteries, and communicates freely with those of the right.

The phrenic or diaphragmatic nerve, connected above with filaments of the pneumogastric, hypoglossal, second and third cervical nerves, and some branches of the brachial plexus, and occasionally with those of the great sympathetic, descends on the anterior and lateral part of the neck, between the rectus anticus and scalenus anticus, and enters the chest between the subclavian artery and vein. The right passes down on the surface of the right lung, beneath the pleura (<p, <p, Plate XXXI.); the left over the pericardium; and both are distributed chiefly to the diaphragm.

The great sympathetic is much more complicated than either of these nerves. It cannot be said to originate from one part more than from another. Though connected with the brain by means of a communicating filament of the sixth pair, it certainly does not arise from that nerve: nor can it be said to arise from the spinal nerves, though connected with them on each side of the dorsal vertebrae. It appears more rational to regard it as a general and extensive network of nervous filaments, which establish a communication between different important organs. Connected above with three ganglions of the neck, the superior, inferior, and middle cervical, and by minute filaments with the lateral-facial, or eighth cerebral, pneumogastric, and glosso-pharyngeal, with which it contributes to form the pharyngeal plexus, it sends off the nervi molles or superficial cardiac nerve. Below the inferior cervical ganglion, generally regarded as a cardiac, the trunk enlarges, and furnishes filaments to the pulmonary and cardiac plexus, the former divided into right or anterior and left or posterior, and the latter into superior and inferior. About the seventh dorsal vertebra, after being connected with all the intercostal nerves and inferior thoracic ganglions, it forms the splanchnic, which, though only the abdominal part of the great sympathetic, may be regarded as a separate nerve. The constituent filaments of this nerve, after being united into two ganglions, the coeliac or semilunar, are resolved into plexiform arrangements, which surround all the principal arteries, and with them are lost in the substance of the organs. Thus the coeliac artery is inclosed by the coeliac plexus; and each of its divisions, the coronary or proper gastric and the gastro-hepatic and gastrosplenic, are inclosed in similar plexiform networks. In the same manner, the superior mesenteric, inferior mesenteric, and renal arteries, have each an appropriate plexus; and those of the colon, bladder, and uterus have small plexiform arrangements, which constitute parts of the same general system. In short, the great sympathetic or intercostal forms an independent nervous system of its own, and though not derived from the dorsal nerves, is intimately connected with them; and its distribution to the organs of digestion, of circulation, respiration, and secretion, is connected chiefly with the associated actions of these organs.

Our limits do not, however, admit of details; and the reader who wishes to understand the minute anatomical relations of these chords, will find the most accurate information in the fourth volume of the treatise of Soemmering (De Corporis Humani Fabrica, Trajecti ad Moenum 1798); in the third of the Descriptive System of Bichat; and in the magnificent illustrations of Walter (Tabulae Nervorum Thoracis et Abdominis, fol. Berolini, 1783) and Scarpa (Tabulae Neurologicae, fol. Ticini, 1794).

PART II.

ANATOMY OF THE ORGANS PERTAINING TO THE ENTRO-PHIC OR NUTRITIVE FUNCTIONS.

The growth of the animal body is effected, and its size and strength maintained, by a class of organs which may be named the Entrophic or Nutritive. These organs agree in the possession of certain common characters, by which they are distinguished from those of the functions of Relation.

The first common character is the want of symmetry in arrangement and harmony in action. Instead of being arranged on the median line, or with similar parts on each of its sides, the organ, or part of the organ, which is on one side, bears no resemblance to that which is on the other. Even in the case of the lungs, though there is a general resemblance, the left differs from the right not only in size and shape, but in the number of its lobes.

It must not be understood, nevertheless, that the organs of this class are altogether void of symmetrical figure. A plane may be made to divide the stomach even into similar halves, so as to leave on each side similar parts of the cardia, of the pylorus, and of the intermediate parts. This plane, however, corresponds not with the mesial plane, but passes transversely from left to right. Nearly the same rule is applicable to other organs.

The second general character of the entrophic organs is, that in action they are not under the influence of the will. The contractions of the muscular tissue of the stomach, and the secretion of its mucous surface, the peristaltic motion of the intestinal tube, the beats of the heart, and the action of the liver, are equally independent of volition. This character Bichat attempted in every instance to trace to independence on the influence of the brain and the cerebral nerves. In one sense this is a truism, in so far as it merely implies that the organs of the entrophic functions do not belong to those of relation. In another sense it is a gratuitous, if not a hypothetical assumption. Though the brain is evidently very intimately associated with the organs of the animal functions, it is not yet determined that it is entirely unconnected with those of the entrophic order. Serious lesion or injury of the brain or the protuberance operates as forcibly on the action of the heart as on that of the muscles of the extremities. On the whole, the safest mode of defining this character is merely to state the independence of the entrophic organs on the will.

Several of the organs of the entrophic function are nevertheless in some degree under the influence of the will. The lungs, for example, by being dilated only by the dilating agents of the chest, are within certain limits under the voluntary power. To this, however, a limit is fixed. Though inspiration or expiration may be effected at the will of the individual, or suspended for a little, very soon the accomplishment of these actions is no longer arbitrary. In like manner, though the bladder is evacuated by the voluntary effort of the individual, the stimulus by which the action is induced is involuntary altogether.

A third anatomical character common to the entrophic organs is, that all of them are situate in the interior of the [7:2:814]trunk, protected by those of the locomotive system; and that they arc lined on one side by mucous membrane, continuous with the external integuments. By means of this arrangement, which is necessarily allied with their property of converting foreign into proper matter, all the entrophic organs, with the exception of the heart, communicate with the surface of the body.

A fourth anatomical character common to these organs is, that though continuous by their mucous investment with the outer surface of the body, their opposite, placed on the outside of the serous membranes, forms shut cavities, not communicating, unless in one instance—the peritoneal end of the oviduct in the female—with the external surface. Whatever be the intermediate substance, these organs are placed between the mucous and serous membranes.

The entrophic organs may be distinguished into two orders, according to the degree of the process performed by each. The nutritive function consists of two subordinate functions, the limitrophic or alimentary, and the haematrophic or circulatory; the first the preparation of the materials destined to be employed in nutrition; the second the distribution of these, after preparation, to the different regions and organs of the system. The organs by which the first process is accomplished constitute the first order; those by which the second is effected constitute the second order.

CHAP. I. THE LIMITROPHIC ORGANS.

The limitrophic organs consist of two divisions; those for digestion of the food, or the chylopoietic, and those for absorption of its nutritious part. The former is effected in successive processes in the divisions of the alimentary canal, a tubular musculo-membranous apparatus, extending from the mouth to the anus. The second is accomplished by an assemblage of minute valvular tubes, the lacteals, terminating in the thoracic duct.

SECT. I. THE ORGANS OF DIGESTION; THE CHYLOPOIETIC

ORGANS.

The organs of mastication have been described already in the fourth section of the second chapter of Part First.

The pharynx, placed on the median line, symmetrical and regular, occupying the upper part of the neck, makes a close approach to the organs of relation, and marks the transition from these to those of the entrophic function. Attached above to the cuneiform process of the occipital bone, behind to the cervical vertebrae, and with the nostrils, mouth, and larynx before, it forms an irregular vaulted apartment about four inches long and two broad at its widest part, and contracting below, where it is continuous with the oesophagus. Besides the opening into this tube, the pharynx presents six apertures; the pharyngeal apertures of the nostrils, the pharyngeal orifice of the mouth, the upper end of the larynx, and the pharyngeal apertures of the Eustachian tube.

It consists of a mucous membrane stretched over loose filamentous tissue inclosed by three muscles, the superior, inferior, and middle constrictor, and attached to the cuneiform process, the cervical vertebrae, and the lateral regions of the neck, by filamentous tissue.

By the superior laryngeal, the pharyngeal, the thyroid, the lingual, and palatine arteries, it receives blood, which is returned by a still greater number of veins to the external and internal jugular trunks. The nerves of the pharynx come from the glosso-pharyngeal, the hypoglossal, the pneumogastric, and the great sympathetic.

• The oesophagus (gula) is a cylindrical musculo-membranous tube, communicating above with the pharynx, and below with the stomach. Placed above between the cervical vertebrae behind and the windpipe before, at the lower end of the larynx it inclines to the left, returns to' the median line at the sternum, bends again to the left at the bifurcation of the trachea, and continues on the left side of the line, passing the aperture of the diaphragm, near the ninth dorsal vertebra, to its junction with the stomach. With the vertebral column behind, at its first inclination it covers the longus colli in the chest, crosses the vena azygos above, and covers the thoracic duct in the middle, and the aorta below. With the jugular veins and carotids on each side in the neck, below it has the trachea on the right, and the recurrent nerve and common carotid on the left; and in the chest it has the aorta on the left and behind. (Plate XXIX. fig. 2, c.)

Lined on the inside by a follicular mucous membrane which assumes longitudinal folds (plicae), the oesophagus consists of two ranges of muscular fibres, the one transverse, the other longitudinal. The first are most distinct at the pharyngeal end. The second form a manifest thick layer through the whole extent of the tube. Externally is a quantity of filamentous tissue, connecting the tube to that of the mediastinum and adjoining parts.

The oesophagus is supplied with blood from the inferior thyroid, thymic, laryngeal, pharyngeal; the aorta by proper oesophageal arteries, the superior intercostale and bronchials, the pericardial, mediastinal, diaphragmatics, and even the coronary of the stomach. The blood is returned by veins equally numerous. The oesophageal nerves proceed from three different sources. Above, it receives filaments from the glosso-pharyngeal and pneumogastric, in the middle from the latter, and below from the pneumogastric and the great sympathetic.

The stomach (ventriculus) is a large pyriform musculo-mcmbranous sac, incurvated on itself (Plate XXIX. fig. 2, and Plate XXXVI. fig. 4), situate in the epigastric and left hypochondriac regions, communicating above with theoeso-phagus, and below with the duodenum. Bounded above by the diaphragm, and the liver, which covers it, it has the spleen attached to its left great extremity, the transverse arch of the colon to the inferior large arch; and its posterior surface corresponds to the duodenum, pancreas, mesocolon, and large abdominal vessels.

The pyriform sac of the stomach is distinguished into a large end or sac (fundus), and a small extremity named the pyloric ; while a particular incurvation of its direction gives it a large inferior arch (arcus major), and a small superior arch (arcus minor). At the left extremity of the latter is the cardia, the orifice by which the oesophagus enters the stomach (osteum oesophageum) ; and from this round the fundus is the large arch. A vertical plane drawn from the cardia divides the stomach into two portions,—the cardiac (fundus, saccus coecus), and pyloric, terminating in an annular contracted opening, about an inch broad (pylorus, ostium duodenale sive pyloricum). Between the two arches is the superior-anterior surface, covered partly by the left lobe of the liver, partly by the left rectus and hypochondre, and the inferior-posterior surface behind.

The stomach consists of peritoneum externally, mucous membrane internally, and an intermediate muscular layer with filamentous tissue.

The peritoneal covering is arranged in a peculiar manner. The anterior fold, meeting the posterior at the small arch, joins it, and forms a membranous production (omentum gastro-hepaticum), connecting the organ to the inferior surface of the liver, where they again separate to invest the upper and lower divisions of that organ. These folds, meeting in like manner along the large arch, where they form similar duplicatures, are again separated to in [7:2:815]close the spleen at the large end, and the colon along the lower division. In the triangular spaces formed by these duplicatures the gastric blood-vessels are lodged.

The mucous membrane, void of epidermis, is covered with minute piles (villi) from the cardiac, where they commence at the fringed termination of the oesophageal epidermis, to the pyloric, where they are continuous with those of the duodenum. It is further puckered into wrinkles (rugae) or folds (plicae), intersecting each other irregularly, and inclosing irregular quadrilateral spaces,— an effect produced-by the contraction of the muscular coat, and connected with the great extent of the gastric villous membrane. In this also are contained follicular glands, especially at the pyloric end and along the two curvatures.

The muscular coat consists of two ranges of fibres, one longitudinal, following the great diameter from the cardia to the pyloric end; the other circular internal, inclosing the circumference of the organ, and most distinct when the organ is empty. On the latter depends the contracted incurvation of the stomach between the cardiac and pyloric divisions. (Plate XXXVI. fig. 4.) Besides these, there are on the left side of the cardia muscular slips expanded on the two surfaces.

The stomach derives its blood from the coeliac artery, the branches of which are arranged in a peculiar and beautiful manner. The coeliac divides into three vessels; one gastric proper, the coronary ; one common to it and the liver, the gastro-hepatic ; and one common to it and the spleen, the gastrosplenic. The first, the coronary, is distributed to the cardiac end, and, lodged in the peritoneal fold of the small arch, proceeds towards the pylorus, distributing branches before and behind. The second, after sending a large vessel to the liver, the hepatic, sends a small one (arteria pylorica), from the pyloric end, towards the gastric, by the superior peritoneal fold, to meet the terminal branches of the coronary; and a large one (gastro-epiploica dextra), by that of the large curvature, to meet the terminal branches of the left gastro-epiploic. The third or spleno-gastric artery, after transmitting a large vessel to the spleen, and various small vessels (vasa brevia) to the large fundus, sends a large vessel (gastroepiploica sinistra), in the peritoneal fold of the large arch, to inosculate with the terminal branches of the right gastro-epiploic. The stomach is in this manner embraced, as it were, by arterial canals above and below. It is further remarkable, that while only one proper gastric artery, of inconsiderable size and limited distribution, proceeds from the coeliac trunk, the gastro-hepatic and gastro-splenic, each not much less than the coeliac itself, send their largest branches to the stomach, and proceeding from opposite ends of that organ, inclose it, meeting by inosculation in the middle of its great and small curvatures. From the capillaries at ↑be fundus, chiefly the vasa brada, the gastric fluid appears to be secreted. The blood, returned by corresponding veins, is poured into the portal.

The stomach receives nerves from the pneumogastric and the great sympathetic. In the stomach the alimentary mass is converted into the pulp named chyme.

The duodenum (ventriculus succenturiatus), about twelve inches long in the human subject, is distinguished by being the most fixed part of the tube in situation. Placed on the vertebral column, and on each side in the cavity of the mesocolon, behind the stomach, and concealed by that organ, it is bounded above by the liver and gallbladder, below by the pancreas and lower part of the mesocolon, and maintains the communication with the pyloric end of the stomach and the ileum. The duodenum is divided by two curvatures into three portions. The first, which is covered by peritoneum, extending from the pylorus to the site of the neck of the gall-bladder, horizontally backwards and a little to the right, descends about two inches almost perpendicularly. With this the second portion, forming an angle, ascends obliquely to the left, and terminates opposite the third lumbar vertebra. The third, forming an angle rather more than right, extends about two or three inches, and terminates at the peritoneal ring, about one inch on the left of the spine, where the ileum commences. The aperture of the common biliary duct, inclosed in a nipple-like process, and the pancreatic, are in the first portion. These curvatures are firmly connected by filamentous tissue; and the bowel retains them even after removal from the body.

The duodenum, void of peritoneal covering, consists externally of cellular tissue, inclosing a range of circular muscular fibres, and lined by villo-mucous membrane, arranged in numerous folds, or valvulae conniventes. The duodenal arteries are derived chiefly from the gastro-hepatic, and are very generally pyloric twigs. This membrane is provided with follicles, first well described by Brunner.

In the duodenum, by admixture of the biliary and pancreatic fluids with the chyme, the latter is prepared for the separation of chyle, which, though more proper to the ileum, is begun nevertheless in this bowel. The comparative immobility of the bowel is requisite, both in consequence of the admixture now mentioned, and also of the fixed situation of the two glands by which the fluids are supplied.

The ileum (ε∕λεov) or small intestine (intestinum tenue), the longest part of the intestinal tube, extending generally from 28 to 30 feet, commences at the annular process above mentioned, and extends to the head of the colon, in which it opens in the right iliac region. It consists of a cylindrical musculo-membranous tube, surrounded by peritoneum, the two folds of which, meeting behind, attach it for the space of three or four inches to the vertebral column, and are again reflected laterally, as described in the first book of this treatise. This attaching membrane is named the mesentery. The great length of the tube, with the small extent of the mesentery, causes it to hang suspended in numerous turns or convolutions. By the ancients this intestine was distinguished into two parts, jejunum or the empty, and the ileum proper; and Winslow idly undertook to fix the limits of this division by referring the two upper thirds to the former, and the two lower to the latter. This distinction, however, for which there is no anatomical foundation, must be rejected as at once arbitrary and useless.

The muscular tunic consists of circular fibres entirely.

The villo-mucous membrane presents numerous valvulce conniventes, which increase its surface to at least double that of its proper area. These duplicatures are most numerous in the upper part of the tube, and diminish as they descend.

The mucous surface of the ileum is peculiar in presenting the piles or villosities in their most perfect form. When a portion of ileum is inverted, inflated, and immersed in pure water, an infinite number of minute processes are seen waving amidst the fluid; but a powerful glass does not enable the observer to determine whether they are round or flat, solid or hollow, obtuse or pointed. Of their shape and structure various accounts are given.

They were first represented, in 1721, by Helvetius, as cylindrical prominences in quadrupeds, but conical in the human subject. According to the microscopical observations of Lieberkuhn, each villus receives a minute lacteal tube, arterial branches, a vein, and a nerve; and in each the lacteal is expanded into a minute sac or bladder (ampullula, vesicula) like an egg, in the apex of which may be seen by the microscope a minute opening.
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On this sac the arterial branches are ramified to great delicacy, and terminate in minute veins, which then unite into one trunk; while its inner surface he represents as spongy and cellular. The space between the villi, which do not touch each other, he further represents to be occupied by the open orifices of follicles, so numerous that he counted eighty of them where were eighteen villi; and both, he asserts, are covered by a thin but tenacious membrane similar to epidermis.

Hewson, while he admits in each villus the ramification of minute arteries and veins, denies the saccular expansion, and infers that the lacteals are ramified in the same manner as the blood-vessels, and that the whole constitute a broad flat body, the spongy appearance of which he ascribes to the mutual ramification of the latter. With this in general Cruikshank agrees; while Sheldon, who found the villi not only round and cylindrical as Hewson, but bulbous as Lieberkuhn, and even sabre-shaped, rather confirms the statements of that anatomist. Maseagni and Soemmering, agreeing in the general fact of vascular and lacteal structure, seem to represent the shape of the villus as that of a mushroom, consisting of a stalk and a pileus.

Some of these discordant statements Hedwig attempts with equal ingenuity and industry to reconcile. The differences in shape he refers to differences in the animals oxamined; and in one class finds them cylindrical (e. g. in man and the horse); in another conical (the dog); in a third club-shaped (the pheasant); and in a fourth pointed or pyramidal (e. g. the mouse). The interior structure he also represents as spongy in all the animals which he examined; and invariably also he found at the apex the orifice of the duct, which, after the example of Lieberkuhn, he conceives constitutes the ampullula.

These conclusions are not exactly confirmed by the researches of Rudolphi, who examined the villi in man and a considerable number of animals. This anatomist never found the orifice seen by Hedwig, notwithstanding every care taken to distinguish it. He maintains that the villi are not alike in all parts of the intestinal canal of the same animal, as represented by Hedwig, but may be cylindrical in one part, club-shaped in another, and acuminated in a third. Admitting their vascular structure, which he thinks may be demonstrated, he regards the ampullular expansion as doubtful, and denies its cellular arrangement.

About the same time Blculand, who had previously examined the intestinal mucous membrane, after successful injection of its capillaries, undertook to revive the leading circumstances of the description of Lieberkuhn. By examining microscopically well-injected portions of intestine, he shows that the villi are composed of a system of very minute arterial and venous capillaries, inclosing a lacteal, which constitutes the ampulla, and in the interior of which a certain order of these capillaries terminates. He also revives the statement of the absorbing orifice at the extremity of each villus.

According to the observations of Beclard, the intestinal villi appear neither conical, nor cylindrical, nor tubular, nor expanded at top, as described by several authors, but in the shape of leaflets or minute plates, so closely set that they form an abundant tufted pile. Their shape varies according to the manner in which they are examined, and according to the part. Those of the pyloric half of the stomach and duodenum are broader than long, and form minute plates; those of the jejunum are long and narrow, constituting piles; at the end of the ileum they become laminar, and in the colon are scarcely prominent. They are semitranslucent; their surface is smooth; and neither openings at their surface, in their cavity, or in their interior, nor vascular structure can be recognised.

The villo-mucous membrane of the ileum is provided with mucous follicles of two orders, the glandulae solitariae and the glandulae agminatae ; the former, like granules, disseminated over the attached surface of the mucous membrane; the latter clustered in bodies at the anterior exterior part. They partake of the general characters of follicular structure.

The ileum is liberally supplied with blood by the superior mesenteric artery, the arrangement and distribution of which may be understood from fig. 4, Plate XXIX.

The nerves arc derived from the solar plexus.

The colon, or large intestine (intestinum crassum), beginning in the right iliac region, extends round the folds of the abdominal cavity, inclosing the ileum, to the left iliac and pelvic, where it terminates in the rectum. Its length is from six to seven feet. The beginning (caput caecum) is a round obtuse bowel, with a minute tubular process, varying in length, named the vermiform. The lower end of the ileum is inserted into the beginning of the colon laterally; and to the part below the insertion the name of caecum or blind gut is restricted. From the caecum the colon descends to the right hypochondre (colon dextrum), where it is connected at the hepatic flexure to the liver by the hepato-colic ligament, two folds of peritoneum, with intermediate filamentous tissue; between the right or hepatic flexure and the left or splenic it is distinguished as the transverse arch (colon transversum), attached to the large arch of the stomach by the gastro-colic margin of the omentum; an angular bend in the left hypochondre forms the splenic flexure; and, finally, after making a long sinuous alternating bend in the left iliac and pelvic regions, named the sigmoid flexure, it terminates in a portion comparatively straight (to tν∂ν, rectum), and following only the antero-posterior incurvation of the inner surface of the sacrum, on which it is placed.

The colon is about two inches in diameter at an average.

The appearance of this intestine is intimately connected with its structure. Inclosed in peritoneum, by the posterior junction of which it is connected to the adjoining organs, it consists of a layer of circular fibres, intersected by three bands of longitudinal fibres. Both are asserted to be muscular; but perhaps the latter are more of the nature of aponeurosis, to give support and resistance to the action of the former. Whatever be their nature, however, they give the colon the appearance of being divided into transverse cells, separated by superficial partitions.

The mucous membrane of the colon possesses the villous character in the caecum and right part, but loses it towards the lower part of the intestine. It is formed into large transverse folds or duplicatures, which separate the internal cells or compartments of the bowel.

At the insertion of the ileum into the colon the mucous membrane of each is prolonged with the submucous tissue, and they mutually meet in two crescentic processes, one superior, small (plica superior, labium superius), the other inferior, large (plica inferior, labium inferius), and approaching, by its greater prolongation, the paraboloid shape. The ileal side of both folds is concave, the caecal or colic convex; and between their free margins, which are rounded, is an intermediate fissure, maintaining the communication between the two intestines. This arrangement, which is named the ileo-caecal valve (valvula Bau-hini, from its supposed discoverer), is supposed to allow the transit of alimentary and excremental matter from the ileum to the colon, but not in the converse direction.

The organization of the rectum is the same as that of the colon generally; but it is uncovered by peritoneum behind. Its lower extremity is surrounded by two circular ranges of muscular fibres, named the internal and external[7:2:817] sphincters. The lower fibres of the levator ani are inserted into its sides.

The caecum and right and transverse portions of the colon are supplied with blood from the superior mesenteric, by means of the colic arteries. The left iliac or sigmoid flexure receives vessels from the inferior mesenteric. The splenic part is supplied by vessels derived from the great anastomotic communication between the superior and inferior mesenteries. (Plate XXIX. fig. 4.) The rectum is copiously supplied with blood from three different sources. The first is the termination of the inferior mesenteric, which is contained between the folds of the mesarectum, under the name of superior hemorrhoidal. The second is the middle hemorrhoidal, or proper artery, derived from the hypogastric or posterior iliac. The third is the internalpudic, the lower or perineal branch of which supplies the sphincter with several branches on each side, distinguished by the name of inferior hemorrhoidal arteries.

The nerves are derived partly from the hypogastric plexus, partly from the sacral branches.

The rectum, like the pharynx, placed between the two classes of organs, entrophic and animal, belongs in some degree to both. As the termination of the alimentary canal, it belongs to the former; but by its sphincters and levator it pertains to the latter.

The appendages of the alimentary canal are two glands, the liver and pancreas, and a cellulo-vascular organ, the spleen.

The liver (hepar, jecur) is a large glandular organ, weighing from two to three pounds, situate in the right hypochondriac and epigastric regions, with the diaphragm above, and the hepatic flexure of the colon and the stomach below. It has a convex upper surface, a concave lower one, a posterior obtuse margin attached to the diaphragm by cellular tissue, and an anterior inferior acute one which is free. The lower surface is distinguished into right and left lobes by a middle pit (sulcus umbilicalis, v. horizontalis), in which the round ligament, the residue of the umbilical vein, is contained, and which is occasionally a canal by an arch of hepatic substance. The inferior surface of the left lobe is divided into anterior and posterior parts by a transverse furrow (sulcus transversus, fossa transversa), in which the trunk of the hepatic arteries, and the portal vein, and the hepatic ends of the biliary ducts, are contained. The margins of this furrow, which are elevated in the lower animals, were named gates by the ancients (σuλα∕, portae), from an erroneous theory. The posterior, which is most prominent, is distinguished by the name of small lobe of Spigelius (lobulus Spigelii). The other distinctions of this surface into lobulus quadratus and lobulus caudatus are immaterial. Between the anterior portal eminence and the umbilical fossa is an oval depression (fovea cystica), containing the gall bladder.

The liver is invested by peritoneum, the folds of which connect it to the neighbouring organs, and retain it in its place. Of these, the most important are the broad and coronary above, the lower or falciform below, and the gastro-hepatic duplicature between the liver and stomach. This forms the investment named capsule of Glisson, in which the portal veins are inclosed.

The structure of the liver is glandular. Two classes of -vessels and a system of tubes are distributed in it; one ramifying into branches and minute tubes, the hepatic artery and portal vein; another, the hepatic veins, converging to a trunk, the vena cava hepatica ; the third, the ρori biliarii, converging into ducts terminating in the hepatic duct. From the researches of numerous anatomists, it appears that the hepatic artery, which is derived from the coeliac, and the portal vein, formed from the veins of the stomach, intestines, spleen, and pancreas, terminate in minute vessels mutually communicating. It appears further, that these capillaries communicate with those of the hepatic veins, and even the origins of the biliary pores; and Soemmering especially infers, that every hepatic acinus consists of hepatic artery, portal vein, hepatic vein, bile-pore, and lymphatic. From this, however, it does not altogether result that bile is secreted from the hepatic arterial blood. Each acinus may require a minute artery for nutrition, a portal venule for furnishing the materials of secretion, a duct for receiving the secreted product, and a vein for returning the residual blood.

The hepatic duct unites at an angle with the cystic, and forming the common duct, terminates in the duodenum. The gall bladder, which is a pyriform bag, with doe fundus below and before, and a neck above and behind, acts as a receptacle for the bile when it is not required in the duodenum. T ∖∖ e fundus, placed between the concave surface of the liver above, and the convex one of the pyloric division of the stomach below, may be compressed by that part of the organ when distended, so as to expel the bile from its cavity.

The pancreas is a flat, oblong, glandular body, measuring from five to six inches in length, and weighing from three to five ounces, contained in the posterior epiploic cavity below the duodenum. It consists of lobules similar to those of the salivary glands. It has a proper artery, from which the pancreatic fluid, very similar to the salivary, is secreted, and conveyed into a small duct. The residual blood is conveyed by a proper vein to the portal.

The spleen (lien) is an oblong hemispheroidal organ, of a deep blue venous blood colour, varying in weight from 6 to 12 or 15 ounces, placed in the left hypochondre, between the fundus of the stomach and the left side of the diaphragm, with a plane surface applied to the former, and a convex to the latter part. The spleen is covered by peritoneum, which, doubling before, forms along the middle of the organ a gastro-splenic omentum, by which it is attached to the stomach. It is generally connected to the colon by a short peritoneal slip.

The intimate structure of the spleen is peculiar. It consists of a number of minute communicating compartments, separated by septa, with white granules intermixed. These cells contain dark-coloured blood; and the organ is indeed more abundantly filled with this fluid than any other in the body. These cells appear to be of the nature of erectile vessels. The splenic artery is very large in proportion to the organ, and apparently communicates by minute terminations with veins, in which the blood is occasionally accumulated.

The principal use of the spleen appears to be, that it serves as a receptacle for a large quantity of blood, which accumulates in the splenic vessels, or flows into those of the stomach, as the latter organ requires. When the stomach is empty, it shrinks; and its blood-vessels, folded on themselves, neither require nor transmit so much of this fluid as they do when the organ is distended. In the latter case the vessels are stretched, their canals are rectified, and the blood flows freely through them. At this period the additional supply seems chiefly to be derived from the spleen. The splenic vessels also appear to contribute chiefly to the secretion of the gastric fluid, which is most abundant at the fundus of the organ.

sect. ii. — the chylophorous vessels.

On the lacteals or intestinal lymphatics it is superfluous to add any thing to what is stated in Book I.

These vessels arise from the villous surface of the ileum, and proceeding between the folds of the mesentery, unite at the vertebral margin of that membranous duplicature, somewhere between the third lumbar vertebra and the äoŗ-tic[7:2:818] opening of the diaphragm. Here they terminate in a jointed irregular tube situate behind the aorta, and which, passing through the aortic opening of the diaphragm, proceeds through the chest between the artery and vena azygos, as high as the sixth, fifth, or fourth dorsal vertebra. Here it inclines to the left, and, passing behind the aortic arch and the left subclavian artery, winds to the left of the latter vessel, and, before the longus colli, ascends as high as the seventh or sixth cervical vertebra, where it terminates in the angle between the internal jugular and subclavian veins, in the trunk of these vessels. This is the thoracic duct. A similar vessel, though smaller, is found on the right side.

CHAP. II. THE HEMATROPHIC ORGANS.

The organs of the hematrophic or circulating function consist of the heart as a central propelling agent, and of arteries and veins as distributing and reducent channels. The hematrophic organs may be distinguished into three orders; first, those of the general or nutritive circulating system; secondly, those of the aerating circulating system; and, thirdly, those of the secreting system. Of these the heart is the central agent; but in the mammalia and man it consists of two divisions, one pertaining to the general arterial, the other to the pulmonary or aerating system.

SECT. I. THE ORGANS OF NUTRITIVE CIRCULATION.

§ 1. THE HEART AND HEART-PURSE.

The heart is a conical muscular organ, containing four communicating chambers, inclosed in a membranous sac, and situate in the anterior middle region of the thorax.

The inclosing sac, named heart-purse, or capsule of the heart (pericardium), consists of two portions or layers, an outer or proper capsular, and an inner or lining division. The outer or proper capsular part of the pericardium possesses the characters of a fibrous membrane, of some density and considerable strength. When washed, its colour is gray or grayish-white, and it appears to consist of minute fibrous threads, arranged without definite order. These fibres are most distinct at its lower margin, where it is connected to the circumference of the tendinous part of the diaphragm. In the young subject it is generally thin and translucent; in adult age or advanced life it is thicker and more opaque. This part of the pericardium is a mere investing membrane, which bounds the region containing the heart, but which extends no further. It embraces the origins of the large vessels above, adheres to the margins of the tendinous centre below, and is on each side connected with the pleura.

The inner surface of the pericardium has the appearance of a transparent or serous membrane, through which the fibres of the outer or capsular part may be seen, and which has the usual glistening aspect of such membranes. It is difficult, however, to insulate it from the outer layer, unless by boiling, when it may be peeled off in minute shreds.

Like the transparent membranes, this inner layer has neither beginning nor end, neither origin nor termination. After lining the inner surface of the proper capsule, it may be traced from the angle at which this capsule adheres to the large arteries and veins, over the auricles, and finally, over the outer surface of the ventricles to the apex of the heart

In this course it preserves the characters of a thin transparent membrane, with a free surface, smooth, glistening, and moistened by a watery fluid; and an attached one, adhering on the one hand to the inner surface of the capsule, and on the other to the outer surface of the heart by means of fine filamentous tissue.

Injection shows that the pericardium consists chiefly of minute arteries and veins. The former are derived from the thymic, phrenic, bronchial, oesophageal, and coronaries of the heart. The substance of the capsular part is probably a modification of the white fibrous system. Nerves have not been traced to any part of this membrane; nor is it ascertained that it contains lymphatics.

Of a general conical shape, the heart (cor) is situate obliquely beneath and behind the sternum, with the base (basis) above and towards the right, and the tip (apex) pointing downwards, forwards, and towards the left. The axis of the cardiac cone lies at once obliquely from right to left and from behind forwards. (Plate XXXI.) The surface may be distinguished into two parts,—the anterior convex, appearing in the space between the right margin of the sternum and the sinuosity of the left lung; the posterior plane, resting chiefly on the oblique surface of the diaphragmatic tendinous centre. These two surfaces are united by a sharp anterior-inferior margin (margo acuta), and an obtuse posterior-superior one (margo obtusa). It generally corresponds in size with the fist of the individual; its average weight in the adult is about ten ounces; and its length from the middle of the base to the tip is about five inches.

The base of the heart is circular, flattened behind, and presents an oblique groove, which indicates the limits between the auricles and the ventricles.

Each auricle is of a tetrahedral shape, and is distinguished into the basilar or membranous part (sinus venosus), and the tip or proper auricle (auricula), a pyramidal angular process, the structure of which is muscular. The right auricle is the largest, the left smaller.

The ventricles constitute the great part of the cardiac cone. Their anterior and posterior surfaces present each a longitudinal depression (sulcus longitudinalis superior et inferior), proceeding from the base to the tip, containing the anterior and posterior coronary vessels, and indicating the situation of the fleshy partition (septum ventriculorum) common to both ventricles.

The interior of the right auricle behind presents above the opening of the superior cava (ostium venosum superius), below that of the inferior cava (ostium venosum inferius), larger, directed obliquely inward, with an intermediate eminence (tuberculum Loweri), denominated after Lower, and the Eustachian valve below (p. 721). Below and anteriorly is the opening into the ventricle, bounded by a round margin (ostium inferius) ; above is the tip presenting muscular bands (musculi pectinati) ; and within is the partition common to both auricles (septum auricularum), with an oval depression (fossa ovalis), the residue of the foramen ovale, occasionally bounded before by a crescentic slip of membrane.

The right ventricle (ventriculus dexter vel pulmonalis) is trilateral pyramidal in shape, with its base above corresponding to the inferior auricular aperture, its apex to that of the heart, the anterior-external wall corresponding with the anterior convex surface of the heart, and the posterior-internal with the common partition (septum cordis). It has two apertures—a right superior, communicating with the auricle; and a left superior, communicating with the pulmonary artery.

To the margin of the superior right aperture (ostium auriculo-ventriculare dextrum), which is round and thick, are attached several membranous triangular folds (laciniae), with two, or occasionally three apices, to which are fixed tendinous chords (chordce tendineae), with their opposite extremities terminating in muscular cylinders (musculi papillares, m. teretes), connected with the fleshy walls of the ventricle. This membranous fold, though often composed of two triangular slips only, is denominated the [7:2:819]three-pointed or tricuspid valve (valvula triglochin, v. tricuspidalis). Its apices hang into the ventricular cavity, and are prevented by the tendinous chords and their muscular bands from being forced back into the auricle.

The left superior aperture (ostium artcriae pulmonalis), corresponding to the beginning of the pulmonary artery which is attached to it, is placed behind the inner slip of the tricuspid valve, by which also it is covered. The inner margin of the pulmonary artery presents three crescentic or semilunar slips, named the sigmoid valves (val-vuloe sigmoideoe), with their convex surface towards the ventricle, and the concave one towards the artery, and minute bodies at the middle (noduli Morgagnii), corresponding to the axis of the artery.

The interior of the left or posterior auricle presents on the right the two openings of the right pulmonary veins, on the left those of the left pulmonary veins, occasionally uniting in a single aperture, to the right and anteriorly the left surface of the septum, bounded before by a small semilunar slip, and below the aperture into the left or aortic ventricle.

The left ventricle has the shape of an obtuse cone, with its base above and behind, and its rounded apex behind and to the left. It is rather larger than the right. The basis has two apertures, a large posterior one, communicating with the auricle (ostium auriculο-ventriculare sinistrum) ; and a smaller anterior, opening into the aorta (ostium aorticum). To the ventricular margin of the former is attached an irregular membranous slip, not dissimilar to that of the right auriculo-ventricular opening, but always terminating in two apices, to which tendinous chords, connected with tapering muscular bands, arc also attached. This has been denominated the bicuspid or mitral valve (valvula mitralis). Like the tricuspid, its apices hang into the ventricle, and are prevented from being re-truded into the auricle by the tendinous chords and papillary muscles.

The aortic aperture, anterior and smaller, corresponds with the commencement of the aorta. Like the pulmonary aperture of the right auricle, it presents three semilunar valves, with the convex surface to the ventricle and the concave to the artery, and with central granules (corpuscula Arantii). These valves are occasionally distinguished into anterior, posterior, and inferior or lateral, according to their relation to the plane of the body. In their aortic side arc generally small hollows, chiefly occasioned by distension of the aorta, named aortic sinuses.

The heart consists Ļ chiefly of muscular fibres, closely united by filamentous tissue, .covered externally by the reflected or cardiac portion of the pericardium, and internally by a proper membrane.

Each auricle consists of two parts,—a membranous-muscular, arranged in the stratified mode (fasciae), distinguished as the sinus ; and a fasciculo-muscular, distinguished as the tip of the auricle, arranged in short parallel bundles (funes). The muscular Walls of the left ventricle are more than double the thickness of the right; and while those of the latter collapse on division, those of the former retain their original disposition. The fleshy pillars of the interior of the right are small and slender compared with those of the left, which are thick and strong.

The arrangement of the muscular fibres of the heart, which has been studied by Senac, Wolff, Duncan, and Gerdy, is peculiar. Though mutually interlacing, like all the muscles of the entrophic order, the external are arranged in layers (strata), while the internal affect the fasciculated form. At the base they are incurvated round the basilar border, and wind obliquely towards the apex ; but as they approach the latter region, more especially in the septum, they observe the longitudinal direction. The assertion of Soemmering, that they are distinguished as being connected without filamentous tissue, is inaccurate.

The adipose tissue at the surface, and towards the base and apex of the heart, appears to be useful in facilitating motion in an organ in incessant action, and forms a soft cushion for the cardiac arteries.

The inner membrane of the heart is thin and transparent. In the right auricle and ventricle, where it is continuous on the one hand with the inner venous membrane, on the other with the inner membrane of the pulmonary artery, it is evidently different from that in the left cavities. It is thinner, and more delicate and transparent. Covering every recess, it is doubled to form the different valvular productions. By Bichat it is believed to be identical with the inner venous membrane; but this is mere supposition. In the left cavities the inner membrane is thicker and more opaque than the right; and its valvular duplicatures, which are much thicker, approach to the fibro-cartilaginous character. This is particularly the case in the aortic sigmoid valves, which often in the healthy adult are firm and elastic,not unlike the palpebral fibro-cartilages. The supposition of Bichat, that it is identical with the inner arterial membrane, with which it is continuous, is, in regard to the ventricle, not improbable.

The heart is supplied with blood from the aorta by means of the right anterior or inferior, and the left superior or posterior coronary or cardiac arteries (artcriae cardiacae), both issuing from the aortic sinus immediately above the anterior and lateral sigmoid valves. The right or anterior coronary artery, lodged in the superior furrow, after sending several large branches to the septum and left ventricle, inosculates at the apex with a large branch of the left or posterior coronary. The latter, which is the largest of the two, after winding round the base of the heart towards the right, is recurvated at the thin margin to the posterior surface, where it runs in the posterior furrow, and is divided into two considerable branches, the larger of which is distributed to the apex; while the smaller, running transversely between the left auricle and ventricle, winds round to the obtuse border, and terminates at the apex, where all the three vessels inosculate freely. The blood is returned by corresponding veins to the coronary, which terminate by one aperture in the right auricle. Its nerves are derived from the pneumogastric and sympathetic.

The four chambers of the heart (atria, atriola) are distinguished into pairs,—a right auricle and ventricle communicating mutually and with the pulmonary artery, and a left auricle and ventricle communicating with the aorta. The auricles, separated by the common septum, do not communicate in the natural state; and though in many hearts an oblique opening exists at the anterior margin of the oval depression passing into the left, the crescentic membranous slip by which it is covered prevents the blood of the right auricle from communicating with that of the left. The ventricles are separated also by a thick, fleshy, common partition, through which there is no direct communication, though it was a favourite subject of inquiry before the time of Harvey, to discover communicating apertures.

The capacity of these chambers varies. The right auricle is always more capacious than the left. The two ventricles are, as near as may be, of equal capacity; and the discordant results obtained on this point by numerous inquirers show merely that any variation is accidental or dependent on the state of the organ during the close of life. The blood found in the right ventricle after death varies from 1∣ ounce to 3 ounces. The capacity of the left, which is generally empty, is estimated by Meckel to vary from 8 to 20 drachms.
[7:2:820]

The blood contained in the right chambers is modena-coloured or venous; that of the left chambers is scarlet-red or arterial. The former is derived from the venae cavae, which open into the right auricle; the latter from the pulmonary veins, which open into the left. The direction in which the blood flows on both sides is from the venous apertures into the auricles, thence to the ventricles, and thence to the respective arteries. The venous blood, on reaching the auricle, distends it, and impels its muscles to contraction; and the cavity thus diminished expels the blood in the only direction in which it can proceed,—by the auricoventricular aperture into the ventricle. This chamber being distended, its muscular walls all round, especially at the base, contract and diminish its cavity, when the blood, extruded, quits the ventricle in the only direction in which it can, viz. by the aperture of the pulmonary artery. The blood from the pulmonary veins follows the same course in the chambers of the left side. The blood of the ventricles is prevented from returning into the auricles partly by the tricuspid and mitral valves, but chiefly by the annidar contraction of the auriculo-ventricular apertures, which are drawn from the margins towards the septum; while the latter is shortened, and the apex is made to approach the base.

§ 2. THE ARTERIES AND VEINS.

Connected with each ventricle is a large tube, in which the blood flows from the trunk to the branches. The pulmonary artery, the first of these, divaricates into a right and left branch, subdivided and distributed respectively to the right and left lung.

The aorta, which is the second, is the large artery which distributes the blood after aeration in the lungs to the system at large.

The aorta, rising from the left ventricle, after giving off the cardiac arteries, makes an antero-posterior incurvation with the convexity upwards, denominated the arch or curvature (arcus aorrae). (Plate XXXI. A, A.) From the upper side of this arch arise three large vessels, the innominata or subclavio-carotid, the common trunk of the right subclavian and carotid arteries (ι), the left carotid (ι), and the left subclavian. The aortic trunk, after this curvature, proceeds downward on the left margin of the dorsal vertebrae, giving oesophageal, bronchial, and superior intercostal arteries, thymic, pericardial, and inferior intercostal arteries successively. From the level of this arch to the parabolic opening of the diaphragm at the tenth dorsal vertebra, it is distinguished by the name of thoracic aorta ; and below this, to the fourth lumbar vertebra, it is the abdominal aorta. At its transit through the parabolic aperture it sends off the diaphragmatic arteries.

The vessels issuing from the abdominal aorta may be distinguished into two orders, those which issue from its sides in pairs, and those which issue from its anterior surface singly only. The former consists of the capsular, distributed to the renal capsules; the renal or emulgent, to the kidneys; the spermatic, to the testes; ’and the lumbar, to the lumbar muscles, and that region generally. The latter are three in number onlv, the coeliac, superior mesenteric, and inferior mesenteric. Opposite the fifth lumbar vertebra, or the fibro-cartilage uniting the fourth and fifth, the aorta terminates by divaricating into two large lateral trunks, the common or primary iliacs (iliacae communes) ; while from its middle behind proceeds a small azygos artery, distinguished as the sacro-médian, along the median line of the sacrum. In this course the aorta is placed in the posterior angle of the thoracic and abdominal serous membranes, and, inclosed by the anterior vertebral filamentous tissue, sends from its posterior surface numerous arteries to the vertebral column and spinal chord.

The distribution of the branches of the aorta may be understood from the following tabular view.
[table]
[7:2:821]

In general the denominations of these arteries indicate the parts to which they are distributed. In the ultimate ’distribution of the arterial system, however, there is great variety; and it is often impossible to determine the exact origin, course, and distribution of the smaller terminations. The trunks alone are constant in position. In distribution, the following general rules are observed :—tø, The arterial trunks send small lateral branches to the parts between which they run. 2<⅛∕, The majority of individual organs are supplied, not by one proper vessel, but either by one principal artery and two or more subordinate ones, or by several subordinate ones. 2>dly, A trunk, after giving off several lateral branches, may either terminate in one vessel, which is ultimately distributed to the organs to which it is destined; or it may divaricate into several, none of which may be considerable enough in size, or direct enough in course, to be regarded as the proper terminal vessel. Thus it is often difficult to determine whether the temporal artery or the internal maxillary is the continuation of the external carotid, which of the palmo-digital arteries is the continuation of the radial, whether the anterior or the posterior tibial artery is the continuation of the popliteal, and whether the dorsal of the foot is the termination of the former, ⅛thly, In the terminal vessels, where inosculation is frequent, it is impossible to determine whether an artery arises from one trunk or another. Thus in the arterial arches of the hand and foot, in which the digital vessels issue from the convexity of the arch, it is impossible to say whether these arteries arise from the radial or the ulnar in the one case, or the anterior or the posterior tibial in the other.

The arteries are accompanied by veins, which in general correspond, for the purpose of conveying the residual blood, after distribution, to the right chambers of the heart, to be transmitted by the pulmonary artery to the lungs for renovation. The veins of the head, chest, and superior extremities, open into the superior cava ; those of the lower part of the trunk, the pelvis and pelvic extremities, terminate in the inferior cava; the veins of the stomach, intestinal canal, spleen, and pancreas, terminate in the portal vein; and the regredient hepatic veins are united in one vessel, which terminates in the upper end of the inferior cava.

SECT. II. THE ORGANS OF AERATING CIRCULATION, OR

RESPIRATION.

The lungs are two soft, spongy, vascular bodies, contained in the cavity of the chest, one on each side, and imitating in shape the internal figure of that region. Each lung, resembling somewhat a cone, with one side truncated, and the base obliquely cut, is distinguished into a convex external surface, corresponding to the concave internal one of the thorax ; a flat inner or mesial surface, corresponding to the mediastinum ; a rounded obtuse apex, corresponding to that of the demithorax ; and a concave base directed obliquely from the mesial plane to the hypochondres, corresponding to the convex surface of the diaphragm.

Each lung is distinguished into lobes (lobi) separated by fissures (incisurae). The right, which is the largest, consists in general of three lobes, the superior, middle, and lower; the left of two only, an upper and lower. The mesial margin of the left is distinguished from that of the right by a sinuous notch, indicating the situation of the heart (fovea cardiaca).

The intimate structure of these bodies, which has been the subject of much research, depends on the nature of the tubes which are distributed to them, and of which chiefly they consist. These are the bronchial or breathtubes (bronchi), the continuations of the windpipe, and the branches of the pulmonary artery and veins.

The windpipe (trachea) is a cylindrical tube, about four or five inches long, extending from the cricod cartilage, to which it is attached by a fibro-mucous membrane behind the sternum, to the level of the third dorsal vertebra, or the fibro-cartilage between it and the second. (Plate XXXI. τ.) It consists of from 17 to 18 or 20 cartilaginous rings (annuli), truncated behind, united by a fibrous membrane without, continuous, but particularly firm in the interannular spaces, and along the whole posterior part of the canal. These fibres are white, firm, longitudinal, and closely set. Within is the mucous membrane, continued from the larynx to the bronchi, resting on filamentous tissue, in which are embedded the mucous follicles. By many, muscular fibres have been represented to exist between the rings; according to Soemmering transversely and longitudinally; and Reisseissen has recently maintained their reality at the posterior part of the tube. Their fibrous disposition is undeniable, but their muscular character may be doubted.

The windpipe, covered before by the thyroid gland, and corresponding to the sigmoid pit of the sternum, is attached to the oesophagus behind by filamentous tissue.

Opposite the third dorsal vertebra the trachea is bifurcated into two tubes named air-tubes (bronchi), which are directed obliquely to each lung with a mutual intermediate angle of about 35°. The right is about one fourth larger and one fifth longer than the left. Both are cylindrical, but divaricate at their lower end, where they sink into the substance of the lungs, into several smaller tubes (bronchia), which again ramify and subdivide into tubes still smaller, and successively. The interbronchial angle is occupied by lymphatic glands, which are also arranged round the tubes.

The bronchi consist of cartilaginous rings, complete above, but parted into three annular segments between the middle and lower ends, united by whitish fibrous tissue, longitudinal externally, transverse within, and lined by mucous solliculated membrane. As they advance into the substance of the lungs, and are still more minutely divided, the cartilages diminish in size and firmness, and their place is supplied by fibrous tissue of transverse circular fibres, which at length also disappear, and mucous membrane alone is left.

These transverse annular fibres have been supposed by Haller, Soemmering, and recently Reisseissen, to be muscular. It is not improbable that they are so; but no positive proof of this fact has yet been adduced, and they appear rather to belong to the elastic fibrous system.

The larger bronchial tubes are accompanied each by aň artery derived from the aorta or the subclavian, and following their ramifications into the pulmonic substance. The blood conveyed by these vessels is returned either to the vena azygos or the superior cava.

The pulmonic or final divisions of the bronchial tubes terminate in blind sacs covered by mucous membrane, and communicate with each other, forming an appearance of intersecting compartments, which have been distinguished by the name of air-cells (cellulae acreae), or pulmonic vesicles (vesiculae pulmonis). They are represented as polygonal and irregular, and about one eighth or one tenth part of a line in diameter. (Haller and Soemmering.) On the whole, these air-cells appear to be merely the terminations of the bronchial tubes mutually communicating, lined by a very delicate mucous membrane.

The pulmonary artery, ramified and subdivided to a great degree of minuteness, communicates most freely with a number of vessels, which may be traced into trunks terminating in the pulmonary veins. This capillary system, enveloped in filamentous tissue, is distributed beneath the mucous membrane of the terminal bronchial tubes or communicating cells. The exterior surface of this filamentous tissue is covered by the pleura. From [7:2:822]these facts it results that the lung consists of cartilaginous and fibrous tubes mutually intersecting, and the capillary communications of the pulmonary artery and veins, inve-loped in filamentous tissue, lined on one side by mucous membrane, covered on the other by transparent serous membranes. The air-cells, lined by mucous membrane, have no communication with those of the filamentous tissue, as some have absurdly imagined. Except this filamentous tissue, the lung has no proper substance or parenchyma ; and its structure is entirely filamento-vascular.

In the capillary vessels of the pulmonary artery and veins, the venous or modena blood, exposed to the influence of the inspired air through the thin bronchial membrane, parts with its dark, and gradually acquires a bright red tint. This may be styled the aerating or ar-terializing capillary system.

The lung, however, receives other vessels, the bronchials, by which its mucous aerating membrane and submucous tissue are nourished. Entering with the bronchial tubes between the folds of their pleura, these vessels are subdivided as they proceed, and at length form a minute network on the attached surface of the bronchial mucous membrane.

The lung derives its nerves from the eighth pair chiefly, and a few filaments from the great sympathetic. The lung is well supplied with lymphatics, both superficial and deep.

SECT. III. — THE ORGANS OF SECRETORY CIRCULATION, OR SECRETION.

Of the organs of secretory circulation, several, as the lacrymal gland, the salivary glands, the liver, and pancreas, have been already considered; and others, for example the testes, will fall under subsequent heads. This, however, is the proper place to notice the organs of the urinary secretion, which consist of two glands, the kidneys, and two excretory ducts, the ureters, terminating in a common receptacle, the bladder.

The kidneys (renes) are two glandular bodies situate in the posterior or lumbar part of the abdominal region, one on each side of the lumbar vertebrae, behind the peritoneum, and before the psoas muscle and part of the diaphragm, with the quadratus lumborum behind and laterally, and enveloped in a thick layer of adipose tissue.

The right kidney is below the liver, above the caecum, behind part of the duodenum, colon, and the right extremity of the pancreas. The left is bounded above by the spleen, by the transverse arch of the colon before, and it has the sigmoid flexure below. The right kidney is about two inches from the outer margin of the vena cava, and the left at about the same distance from the outer margin of the aorta.

The situation of the right kidney is generally lower than that of the left, so that part of its lower extremity is in the iliac fossa, while the lower extremity of the left is quite above the margin of the ilium.

Resembling in general shape the large French bean, named from it, each kidney may be described as an oblong body, convex externally and at both ends, and with a sinuosity at its inner margin, named the renal fissure (fovea renis), in which the vessels and excretory duct are contained. Each kidney is between four and five inches long, and two broad; and the weight of each varies from three to four ounces. The anterior surface, corresponding but not attached to the outer surface of the peritoneum, it convex, but becomes hollow at the inner margin, where it terminates in the renal fissure. The posterior surface, which is less convex, is separated from the internal aponeurosis of the transverse abdominal muscle, the diaphragm, and the psoas magnus, by a thick layer of adipose tissue.

The kidney consists of glandular structure, invested by a firm membrane, somewhat fibrous in appearance.

In the glandular structure the anatomist recognises the I most distinct example of this form of tissue. It consists of two parts, a granular external, and a tubular internat The former, which occupies the exterior of the kidney, is a homogeneous substance, of a yellow fawn colour, and consists of minute spherical or spheroidal granules (granulo), aggregated together by filamentous tissue, and forming at their exterior calycoid or cup-like cavities, in which the round fundi of the tubular conoids are lodged. In these the capillary vessels of the kidney are ramified with great minuteness. The tubular part consists of very minute capillary tubes (tubuli uriniferi, tubuli Belliniani), varying in length, united by filamentous tissue, and arranged in parallel juxtaposition, so as to form conoids with globular bases, which are lodged in the cup-like cavities of the granular portion, and rounded apices directed to the renal fissure. The number of these tubular cones varies from 10 or 12 to 18 or 20. Their apices form an equal number of nipple-like processes (papilloe), covered by a thin membrane almost transparent, in which are numerous minute holes, apertures of the tubes of which the cones are composed. These apertures, however, are much less numerous than the tubes, several of which are united in one common orifice. The renal papilloe thus constituted project into a series of conical cavities, formed within of the papillary membrane, without of fibrous strata and filamentous tissue. These cavities, which from their shape are denominated funnels (infundibula, calyces), uniting into three or four larger ones, terminate in a considerable membranous sac named the basin (pelvis) of the kidney.

These two parts of the kidney are distinguished not only in structure but in colour and consistence. While the granular part is fawn-coloured, and somewhat soft and flabby, the tubular is pink-red, fleshy and firm; and the boundary line is distinct. The tubular cones are separated from each other by partitions, which appear to be filamentous tissue.

There is no doubt that the granular is the secreting part of the gland; and the tubes are merely conduits of the urine, which indeed may be expressed from their apertures. It is important, however, to determine the mode in which the two portions communicate. The assertion of Ferrein and Eysenhardt, that the tubes are blind canals, is inaccurate in this respect, that the terminal tubes evidently communicate with others in the interior of the cones, which again are immediately connected with the granular part. It further appears, that in the granular part there are very minute white tortuous canals, which appear to communicate with the straight tubes of the cones. All beyond this is entirely conjectural.

The kidney, therefore, cannot be said to possess parenchyma or proper substance. The idle distinctions into cortical and medullary ought to be rejected as remnants of an exploded theory.

The kidneys are supplied with blood from the aorta by the renal arteries. Issuing at right angles from the lateral regions of the abdominal aorta, below the superior mesenteries, these vessels pass directly into the fissure at its superior and anterior part, the left behind, the right occasionally before the renal vein, but crossing its direction. The calibre of these vessels is considerable, about three lines at least; and they have been estimated to convey the sixth part of the blood of the abdominal aorta. The left artery is about one inch long, the right is the whole breadth of the vertebral column longer. In the renal fissure each artery divaricates into three or four consider·
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able branches, which enter the kidney a little above the attachment of the basin (pelvis). These vessels are again subdivided into an anterior series before, and a posterior cluster behind the infundibula, which they accompany to the papillae. Dividing more minutely, they form anastomotic arches, from the convexity of which proceed minute vessels, radiating into the granular substance of the gland. These vessels are distributed principally to the granular matter at its calycoid surfaces, in which the tubular cones are lodged.

The veins are arranged exactly in the same manner, and connected with the renal trunk, much as the arterial branches are connected with it.

The kidney is supplied with nerves, accompanying the arteries, derived from a plexus inclosing the renal trunk, and which is originally formed from filaments of the solar of the great sympathetic.

The pelvis consists externally of a prolongation of the renal investment, a proper middle membrane, white, opaque, and fibrous, and an inner lining, which, though thin and semitransparent, presents the character of mucous membrane.

The upper extremity of each kidney is covered by the renal capsule, a substance of no peculiar structure, and the nature of which is unknown.

The basin forms the common termination of the renal funnels, and the commencement of the ureter. This is a membranous tube, of the diameter of a moderate-sized quill, passing between the renal basin, behind the peritoneum, to the posterior and inferior part of the bladder, in which the lower extremity opens. Each ureter is inclined to the mesial plane below. The right ureter is on the outside, and nearly parallel with the inferior cavity. Both cross the psoas at an acute angle, and below the common iliac arteries and veins. In the pelvis they cross the vas deferens in the male, and on reaching the bladder pass obliquely, from eight lines to an inch, through its coats, and open in the posterior margin of the lower fundus of that organ.

These tubes consist of fibrous membrane, lined by mucous and covered by filamentous tissue. It contains no muscular fibres, notwithstanding the assertions of some.

The ureters are supplied with blood derived from the renals, occasionally from the lumbars and spermatics, but more especially from the aorta by two ureteric arteries.

The urinary bladder is a muscular membranous bag, spherical above and cubo-spherical below, placed on the lower region of the pelvis, behind the pubal symphysis, and before the rectum in the male, and the uterus in the female. From the peculiarity of its figure and relations, it is distinguished into a superior∕wn<⅛s, spheroidal, directed to the abdominal cavity; an inferior fundus, cubo-spheroidal, between the ureters and urethral opening; a neck (cervix), pyriform at the latter point; an anterior surface, corresponding to the posterior of the pubal symphysis; a posterior, corresponding to the rectum in the male and the uterus in the female; and lateral regions, corresponding to the ilio-ischial inner surface, and those of the obturator internus and levator am.

In females generally the transverse extent of the bladder is greater than in the male, and in females after childbearing than in the virgin. In infancy its superior fundus is pointed and conical rather than globular,—a peculiarity derived from its foetal shape, which is pointed, with the urachus, a ligamentous chord proceeding to the navel, attached.

The bladder consists of a muscular coat, covered above, behind, and laterally by peritoneum, and lined by mucous membrane.

The peritoneal covering is continued from the anterior surface of the rectum, and the lateral regions of the pelvis over the posterior and lateral and part of the superior surfaces of the bladder, all of which are free; while the inferior fundus, the neck, and the anterior, are covered by filamentous tissue, connecting the organ to the neighbouring parts. This filamentous tissue is abundant, especially below.

The muscular coat, always distinct, varies in thickness in different individuals. In females, so far as we have observed, it is rather thicker than in males. The fibres run in all directions, but are strong at the superior surface, where some anatomists have arbitrarily distinguished them by the name of detrusor urinoe. There are no fleshy pillars, mentioned by some, in the healthy state.

The neck is surrounded by a thick range of circular fibres, which has been denominated the sphincter of the bladder.

The mucous membrane, without villi or epidermis, is extended over the whole inner surface of the organ, and is continuous behind with that of the ureters, and before with that of the urethra. The space inclosed between these three orifices is named the vesical triangle (trigorius vesicae); and a minute duplicature of the mucous membrane at the urethral orifice is denominated the vesicae uvida.

The bladder is supplied with blood chiefly from the posterior iliac or hypogastric trunk, by means of the common pudic, the obturator, the ischiatic, and the hemorrhoidal. Of these, one vesical artery proceeds from the hemorrhoidal; another often comes off directly from the hypogastric as an inferior vesical; and in some instances they issue from the umbilical. The vesical nerves are partly from the sympathetic, partly from the sacral.

The capacity of the bladder varies in different individuals. In the female it is generally more capacious than in the male. In the healthy state it may contain a pound of urine, without extreme distension; and it is often capable of containing two, three, or four pounds. Its situation varies at different periods of life, and in different degrees of distension. In the foetus and infant, when the pelvis is small, the bladder is contained in the abdomen. In the adult in the ordinary state it is within the limits of the pelvis; but when much distended, its superior fundus, rising above the pubis, is in the abdomen. During pregnancy, also, it is thrust forwards and upwards by the gravid womb.

Urine, the fluid secreted by the kidneys, is particularly distinguished by containing, with various saline substances, urea, an animal principle containing 46 per cent, of azote. As the saline ingredients also abound in principles containing this element, it may be inferred that the chief purpose of the kidneys is to remove from the system a considerable proportion of nitrogen, which would either be injurious by its presence, or disturb the due proportion of the other elements.

The urethra, which terminates the urinary apparatus, is nevertheless common to it with the reproductive organs. The male urethra especially is more connected with the reproductive than the secretory organs. In the female, in whom alone this canal is proper to the latter, it is a short muco-membranous tube, terminating in a papillated orifice in the superior anterior wall of the vagina.

PART III.

ANATOMY OF THE ORGANS PERTAINING TO THE REPRODUCTIVE FUNCTIONS.

These organs, by the possession of which the individuals of the human race are distinguished into two sexes, male and female, consist in the former of impregnating, and in the latter of the impregnable organs. The former may be again distinguished into preparing and transmitting [7:2:824]Organs; and the latter into receiving and ootrophic organs, or those which nourish the product of generation.

CHAP. I. — THE MALE OR IMPREGNATING ORGANS.

The male organs consist of two glandular organs, named testicles with excretory ducts, for secreting the impregnating fluid, and an organ for transmitting it to those of the female.

The testicles (testes') are two ovoidal bodies contained on each side of the mesial plane in a cutaneo-cellular sac named the scrotum, attached to the anterior inferior part of the pubal symphysis.

The scrotum consists of skin with very thin corion, resting on loose filamentous tissue, which forms on the mesial plane a thick wall, separating the right half of the scrotal bag from the left. On the median line is a superficial groove, named suture (raphe), at which the corion and filamentous tissue, elsewhere loose, are united into a solid and firm substance. Most of the old anatomists mention a muscular layer known by the name of dartos, and to which they ascribe the contraction of the scrotum on exposure to cold; but the existence of this muscular layer is not supported by inspection. The scrotal skin is well Supplied with arteries, and especially veins connected with those of the epigastric, external iliac, femoral, obturator, and external pudic, the branches of which anastomose freely. The nerves are from the lumbar, obturator, and crural.

The scrotal filamentous tissue incloses on each side a thin membranous sac of a pyriform shape, with the base below, and tapering to a neck above. Adherent on the outside to the filamentous substance, this membranous sac is free and smooth within, except at the neck, where it embraces a part distinguished by the name of spermatic chord. This, which is the sheath-like or vaginal coat (tunica vaginalis), is distinguished into two parts, an inferior pyriform, forming a cavity for the testicle, and a superior cylindrical, covering the spermatic chord, and adhering to it. This membrane is said to be fibrous externally; but it appears to be merely condensed filamentous tissue. Within it is evidently a transparent serous membrane, both in qualities and distribution. It is continued from the adherent part of the chord downward, and over the testicle.

Within the cavity of the former are contained the testicles, both suspended by the spermatic chord, with the epididymis behind. Their substance is inclosed in a firm, opaque, white, fibrous investment, covered by a thin transparent membrane, reflected from the vaginal coat. The former is the tunica albuginea, or proper tissue of the gland; the latter is the vaginal coat of the testicle (tunica vaginalis testis).

The testicle consists of minute irregular-shaped granules, of a white or gray-white colour, soft, closely compacted, and with numerous capillaries distributed through them. More minutely examined, these are found to be capillary tubes of extraordinary length, folded on themselves, and contorted so as to occupy a small space, and when unfolded extending, according to some anatomists, 16 feet, according to others to 25 or even 100 ells. These long tortuous tubes, which are named the seminiferous (ductus seminiferi), are estimated at about 300 in number. They communicate by one extremity with the bloodvessels and lymphatics of the testicle, and by the other, after several unite into one common duct, terminate in about 20 larger tubes, denominated egredient ducts (vasa efferentia), which, united in a cluster by means of filamentous tissue, and invested by part of the tunica albuginea, form at the upper part of the gland a whitish cylindrical body, about six lines long and two broad, distinguished by the name of the process of Highmore (corpus Highmori). These efferent vessels unite and form a single' tube of great length, which, folded on itself by innumerable turns, connected by filamentous tissue, and invested by tunica albuginea, constitutes the epididymis, attached by its head to the testicle, and by an incurvated extremity∣ named tail, continuous with the common excretory duct (vas deferens).

The latter is a long fibro-cartilaginous tube, ascending upwards from the tail of the epididymis, and making part of the spermatic chord, with which it enters the abdomen at the inguinal aperture. At the inner margin of this it separates from the chord, and descends into the pelvis, first by the side, then at the posterior and inferior fundus of the bladder; and, approaching that of the opposite side with the vesicula seminalis on the outer margin, each vas deferens is in contact with the other at the base of the prostate gland. Here each receiving a tube from the corresponding vesicula, forms a common duct (ductus ejaculans), which traverses the prostate, and terminates in the urethra about one inch and a half from its vesical end, on each side of the eminence named veru-montanum.

The spermatic chord, by which the testicle is suspended, consists of the spermatic artery or its divisions, derived in general from the aorta, two or three spermatic veins, several lymphatics, and the vas deferens, inclosed in filamentous tissue, and covered by a slip of muscular fibres denominated the suspensory muscle (cremaster, tunica erythroides), detached partly from the internal oblique and transverse of the belly, fixed partly at the inner surface of the ligament of Poupart and the tuberosity of the pubis.

The spermatic artery divaricates into several branches, which are distributed, after a few sent to the epididymis, among the seminiferous ducts. They communicate with numerous tortuous veins, which are collected into a cluster known by the name of the pampiniform body, situate immediately below the tunica albuginea.

Below the inferior fundus of the bladder, on the outside of that organ, are placed two bodies, oblong, flattened, pyriform, with the base behind, composed at first sight of a series of cells separated by septa. Each of these bodies, which have been named the seminal vesicles (vesiculae seminales), consists of a long tortuous membranous tube, convoluted on itself, and with the folds aggregated by bridles of filamentous tissue, which convert it into communicating sacs. The cavity of this canal, which communicates with the urethra by a tube, common to the vesicles and the vasa deferentia, has been supposed to serve as a reservoir for the seminal fluid after secretion by the testicles; but this supposition is by no means verified, and is open to several objections.

The transmitting organs consist of the penis with the urethra and prostate gland.

The penis, the shape of which is well known, consists, of two parts, the cavernous body (corpus cavernosum), and the spongy body (corpus spongiosum) containing the urethra. The cavernous body, single before, bifurcated behind, may be described as two cylindrical bodies, inclosed in a fibrous investment, which, uniting them on the mesial plane, forms a partition (septum medium), perforated nevertheless with orifices for vessels. The divaricating posterior extremities (crura) are firmly attached to the ιschio-pubal rami on each side. The intermediate triangular interval is occupied by the perineal filamentous tissue, fat, the perineal muscles, and the spongy body in the middle. Above and before, both are connected to the pubal symphysis by a triangular, flat, fibrous substance, named the triangular or suspensory ligament.
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The spongy body is a cylindrical cellulo-vascular tube, inclosing the urethra, and occupying the middle depression, along the lower surface of the cavernous body, from ’its anterior extremity, where it constitutes the glans, to the angular bifurcation of the cavernous body, where it is expanded into a substance denominated the bulb of the urethra. The spongy body is invested on the side and below by integuments only.

Both these parts, but especially the cavernous body, consist of numerous minute arteries, communicating directly with elongated and dilatable veins, and constitute the best example of erectile arrangement in the body. The injection of these vessels constitutes the erection of the penis, and induces the contraction of the urethra necessary to expel the seminal fluid. The two extremities of the spongy body, the glans before and the bulb behind, form the limits of the erectile tissue round the urethra. The anterior extremity is covered by loose skin, which forms the foreskin (prceputium), and, in the shape of a thin semimucous corion, provided with epidermis, is continued over the glans, from which it passes insensibly into the mucous membrane of the urethra.

With the penis several muscular organs are connected. The ischio-cavernosus and transversus perinoei on each side connect the cavernous body to the ischium; and the bulbο-cavemosus connects it to the bulb of the urethra. Mr Houston of Dublin has lately discovered a packet of muscular fibres situate between the pubal arch and the penis on each side, which, by compressing the dorsal vein, may, he imagines, contribute to erect the organ.

The cavernous and spongy bodies are supplied with blood from the terminal end of the internal pudic artery, by means of two vessels, the cavernous and the dorsal. The bulb receives branches from the transverse perineal artery.

The prostate gland is a body cordiform or flat conoidal in shape, with the base behind and the apex before, corresponding to the vesical end of the urethra, situate behind the pubal symphysis before, and below the neck of the bladder, in the angle between it and the rectum, and between the levator ani of each side.

It is distinguished into three lobes,—two lateral, united on the mesial plane,—and a small cellulo-vascular slip in the angle between them, towards the base. In structure it is composed chiefly of minute arteries and veins ramified in a firm, fleshy, filamentous tissue, amidst which are placed follicles with minute ducts, which terminate in larger tubes, varying in number from seven to twelve, the apertures of which are on the sides and the surface of the urethra. These follicles secrete a viscid liquor, the use of which is unknown. From the fact, however, that, when the prostate gland is diseased or injured, the sexual appetite is languid or extinguished, it may be inferred that the prostate is essential to the generative functions in the male. It is analogous to the uterus in the female.

With the prostate may be mentioned the accessory glands of Cowper, two small bodies, oblong-round, placed on each side of the urethra, before the prostate. They appear to be mucous follicles on the large scale.

The urethra is a membranous canal, extending from the neck of the bladder in the pelvis to the extremity of the glans, where it terminates on the surface by an aperture (orificium urethroe), consisting of two lateral segments. Its length and width vary in the erect and unerected state of the penis. In the latter it is about seven or eight inches long, and its calibre is about three lines, but admitting of distension beyond this. According to the parts with which it is connected, it is distinguished into four different portions; 1sZ, the prostatic, about one inch; 2d , the membranous, from one to one inch and a half; 3<7, the bulbous, scarcely one inch; and, ⅛th, the spongy portion, occupying the anterior part of the canal, inclosed by the spongy body.

The surface of the urethra is a mucous membrane supplied with follicles, and moulded into blind sacs named laxunae, which appear to contain mucous ducts. Its capacity varies in different parts. Wide at the middle of the prostate, it is contracted in the membranous part, which is indeed the narrowest of the canal; it enlarges again in the bulb; and from this it preserves the same diameter to immediately behind the glans, where it forms a dilatation distinguished by the name of the navicular (fossa navicularis). The apertures in this canal have been already mentioned to be, besides that of the bladder, one ejaculatory on each side of the veru-montanum, from seven to ten excretory apertures from the prostatic ducts, and one aperture from each accessory gland. The mucous membrane of the membranous and spongy portions presents longitudinal folds, which appear to be connected with the occasional distensions of the tube for the expulsion of the urine.

The urethra, straight in direction on the mesial plane, is incurvated within the pelvis from behind forwards, so that its concave incurvation incloses the pubal arch, while its convexity is turned to the perinaenm. The pendulous state of the penis, when nncrected, causes it to acquire another incurvation without the pelvis, with the convexity directed upward. These curvatures are considerably exaggerated in engravings. The first round the arch of the pubis is much less angular than it is delineated.

CHAP. II. THE FEMALE OR OOTROPIIIC ORGANS.

The female generative organs consist of the ovaries, the uterine or Fallopian tubes, the womb, and the vagina. These organs are contained in the pelvis.

From the time of Steno, anatomists have given the name of ovaries or eggbeds (ovaria) to two ovoidal bodies, about the size of a pigeon’s egg, placed one on each side of the womb in the pelvis, in a duplicature of peritoneum termed the broad ligament (ligamentum latum) of the uterus. Convex and free on their anterior and posterior surfaces, and tapering towards each extremity, their lower margin is straight or slightly concave, with a vascular sinuosity. The external extremity is contiguous to a round solid chord (ligamentum teres), forming the anterior margin of the broad ligament, and proceeding from the womb to the internal orifice of the inguinal canal and the pubal extremity of the ligament of Poupart, and by which the uterus is retained in the pelvis. Each ovary weighs about one drachm and a half.

Covered externally by peritoneum, stretched over a< fibrous membrane of some firmness, the ovaries consist of a pulpy brownish-gray substance, very vascular, in which l are embedded minute bodies of vesicular appearance and oval shape, varying in number from 15 to 20. These bodies, which, from the time of De Graaf at least, have been regarded as ova or embryal atoms or germs (ova Graafiana, ovarii vesiculae), consist of a thin membrane containing a viscid, reddish, or yellow fluid.

The ovary is supplied with blood from arteries analogous to the spermatic of the male.

Previous to puberty the ovaries are smooth in surface and entire. After this period, both in females who have had children, and even in virgins, they are marked on the surface by minute depressions, which have been denominated cicatrices, and which are believed to be the consequence of minute breaches of the ovarian tunics, occasioned by the escape of the vesicles from the surface of the ovary. There is no proof that these cicatrices are the invariable result of sexual intercourse. Small before puberty, at that period they acquire considerable size, and [7:2:826]retain them till the age of 45 or 48, after which they shrivel and shrink to a very small size.

The Fallopian or uterine tubes are the excretory ducts of the ovaries. They are cylindrical tubes about four or five inches long, contained in the anterior fold of the superior margin of the broad ligament, between the round ligament and the ovary, and connected by their lower extremity with the superior angles of the womb. Their superior extremity, which is loose, is surrounded by a fringed or laciniated slip of peritoneum, in the centre of which is seen the upper or peritoneal aperture (orificium superius), larger than the calibre of the canal, which admits a hog’s bristle, but contracts at the lower or uterine extremity (orificium uterinum), which is situate in the upper angle of the inner surface of the womb.

Covered by serous membrane externally, lined by thin mucous membrane with follicular glands, the Fallopian tubes consist of fibrous tissue interposed between these two. Below, however, at their junction with the womb, they seem to partake of the structure of that body.

The womb (uterus, matrix) is a hollow organ with thick walls, shaped like a conoid, flattened before and behind, situate on the mesial plane in the pelvic cavity, between the bladder before and the rectum behind. Small before puberty, at that period it is about 2 1/2-inches long, l 1/2 broad at its widest part, and weighs from 7 drachms to 1 1/2 ounce. It is distinguished into the fundus, body (corpus), and neck (cervix) ; the first free, directed upwards; the second also free, between the bladder and rectum; and the third connected within and below to the vagina. At each side of the fundus is a corner or angular part, which communicates with the uterine extremity of the Fallopian tube. The neck of the womb may be distinguished into the external or peritoneal, and the internal or mucous neck, which terminates in an elliptical opening, with rounded, thick, firm margins, not unlike the mouth of the tench, and named therefore os tincae, as well as os uteri. These lips become rough and irregular in women after child-bearing, in consequence of the distension during parturition.

The cavity of the womb is small compared with the volume of the organ, in consequence of the thickness of its containing walls. It is triangular in shape, with the base at the fundus, and the apex at the neck. The superior angles are small recesses, in which the uterine extremity of the Fallopian tube of each side opens. The cavity is much contracted at the neck, forming a short cylindrical canal, the lower aperture of which is the os uteri, communicating with the vagina.

Covered externally by peritoneum, the womb consists of a peculiar thick, firm, whitish substance, lined by mucous membrane. This intermediate matter, though neither red nor distinctly fibrous, has been very generally regarded as muscular. Its contractile powers during parturition it is impossible to doubt. But while it is difficult to reconcile this phenomenon with the absence of muscular tissue, it must be allowed that it is much more easy to maintain than demonstrate the unequivocal appearance of muscular fibres. On this topic the reader may consult a paper by Mr Charles Bell, in the 4th volume of the Medico Chirurgical Transactions ; and an elaborate account of the different ranges of muscular fibres in the uterus, by Madame Boivin, an eminent Parisian accoucheuse, in her Memorial de (Art des Accouchemens, Paris, 1824.

The uterine mucous membrane is thin, but reddish-gray, villous, and marked by numerous pores, the apertures of blood-vessels, most probably those which secrete the menstrual fluid. At the neck it is provided with muciparous glands, which are the seat of several of the forms of leucorrhoea.

The blood-vessels of the uterus are derived partly from the spermatic, partly from the hypogastric. The former, after passing between the folds of the broad ligaments, and giving branches to the tubes, enter the uterine substance by its lateral regions. The second, named the uterine, after sending branches to the vagina and neighbouring parts, ascend along the margins of the organ, and are distributed to itsjfimćføs.

The uterine veins correspond to the arteries in course and connections. In the walls of the organ they form large sinuses, very distinct after parturition.

The uterine lymphatics are connected with those of the pelvis and hypogastric region. The nerves, which are numerous, proceed from the lower extremity of the great sympathetic, from the renal plexus, the spermatics, the last lumbar nerves, and the sacral.

The womb is the proper ootrophic organ, to the inner surface of which the ovum is attached by a vascular body denominated the placenta or after-birth.

The vagina is a membranous vascular tube, situate on the mesial plane, behind the pubal arch, and before the rectum and urethra, and extending from the neck of the womb in the pelvic cavity to the external outlet (vulva), where it is continuous with the surface. Not exactly cylindrical, but flattened before and behind, its length is about four inches, its breadth one, but very distensible. It is generally distinguished into the upper vaginal recess (vaginae fundus), inclosing the neck of the womb behind the os tincae, the lower vagina (vagina propria), and the vaginal opening (vulva).

The vagina consists of mucous membrane surrounded by filamentous tissue, a vascular network, and some muscular fibres. The mucous membrane, which is red below, gray above, and not unfrequently marbled, soft and spongy, is disposed in numerous large transverse and semicircular folds (rugoe) on the anterior and posterior surfaces. In the recesses of these folds are numerous pores, evidently the source of the mucous viscid secretion which is so abundant on this membrane, during sexual excitation, at the period of parturition, and morbidly in gonorrhoea in the female. On the lateral regions it presents pyramidal eminences (papillae).

The mucous membrane is connected by filamentous tissue to another, which in the vicinity of the uterus is compact, firm, and elastic, and below, towards the orifice, is thinner, and contains a network of numerous communicating vessels, in which the blood is occasionally accumulated in the manner of erection. The lower extremity is inclosed laterally by some muscular fibres (constrictor'vulvoe), which are believed to have the effect of contracting the vagina voluntarily, and by which, when continued, as they occasionally are, to the base of the lαbia magna, women, according to Soemmering, may move these parts. The vaginal membrane is provided with lymphatics connected with those of the pelvis. The nerves, which are numerous, and some of which appear to terminate in the pyramidal eminences, are derived partly from the sacral, partly from the crural trunks.

The vagina terminates in the vulva, an opening formed within by the clitoris before, the hymen behind, and the nymphoe or labia parva on each side; externally by the mons veneris before, the frenum and navicular fossa behind, and the labia magna on each side.

The clitoris is a small, oblong, conical process, consisting of erectile vessels, covered by mucous membrane, attached to the lower margin of the pubal symphysis. The hymen is a crescentic fold of mucous membrane, surrounding the sides and posterior part of the vagina. The small lips or nymphoe (labia parva) are two crescentic bodies, consisting chiefly of erectile vessels, contained within a duplicature of semimucous membrane. With these the inner surface of the labia is continuous; and they consist [7:2:827]chiefly of filamentous tissue, placed between semimucous membrane and skin.

Connected with the female ootrophic organs are the ’breasts or mammae.

The female of the human species has only two breasts; and their position on the anterior and superior part of the thorax, on each side of the mesial plane, is a character which, with those of the locomotive apparatus, indicates distinctly the erect biped attitude.

Of a hemispherical or conical shape, the female breast consists of a glandular organ, named the mammary, surrounded by adipose tissue, and covered by integuments. It is distinguished into the breast (mamma), the nipple (papilla, mammilla), and a coloured ring of skin (areola).

The gland is of a flat, rounded figure, and consists of lobes of white pulpy substance, separated from each other by filamentous tissue, and which may be resolved into granules or acini about the size of millet seeds, which again arc composed of minute oblong vesicles disposed in a radiating manner. From the granules or acini proceed minute tubes named the lactiferous (ductus lactiferi, tubuli galactophori), which uniting into larger tubes, varying in number from 20 to 30, terminate in the centre of the mammary gland, behind the areola in conical dilated sacs (sinus), varying from one or two to three lines in diameter. These galactophorous ducts, which are larger than in any other gland, are formed of mucous membrane, which extends into the sinuosities, and is at the nipple identified with the skin. Several of the lactiferous tubes arc said to originate from the adipose tissue of the breast; but this seems merely to indicate that they communicate with the vessels of this substance. The lactiferous tubes arc indistinct before puberty, small in the virgin, and in general in the sterile, and during the intervals of pregnancy, and large only at the close of that period, and during the process of suckling.

The nipple of the female breast is a flat, conical process, the shape of which is well known, consisting externally of skin, with thin delicate corion and epidermis, internally of mucous membrane, and an intermediate network of dilatable arteries and veins mutually and freely communicating. These parts are united by filamentous tissue, which varies in quantity at different periods. But from the vessels now mentioned the nipple derives its property of occasional erection, especially under the influence of mental emotions.

The breast derives its blood from the internal mammaries, the intercostals, and the thoracics or external mammaries, ’the branches of which penetrate between the lobules of the gland. It has lymphatics, though not more abundantly than any other organ. The nerves are chiefly cutaneous.

The mammary gland is separated from the pectoral muscle by a thick cushion of adipose substance, on which it rests; and it derives a gentle conical elevation from the subcutaneous adipose tissue. The mammary skin is remarkable for the delicacy and softness of the corion.

CHAP. III. THE PRODUCT OF GENERATION.

The ovum or impregnated germ, the result of the union of the sexes, consists of an embryo or new animal, inclosed in several membranes, and attached to the inner surface of the uterus by a vascular mass.

Of the membranes, one, the decidua (epichorion), belongs to the uterine surface; the other two, the chorion and amnion, belong to the foetus or embryo. The decidua consists of two parts, an external (decidua vera), and an internal (decidua reflexa) ; both modifications of albuminous secretion. The chorion, the outer covering of the foetus, is a thin transparent membrane, covered with villosi ties on both surfaces, but especially the external. The amnion is a thin transparent membrane, adhering feebly by its external surface to the inner of the chorion, and inclosing a watery fluid, variable in quantity, in which the foetus, suspended by the umbilical chord, floats.

The umbilical chord (funis umbilicalis) consists of, 1st, one vein and two arteries, inclosed in— 2d , a soft, semifluid, gelatinous substance, named from Wharton gelatina Whar-toniana; 3d, the urachus, a ligamentous chord proceeding to the superior fundus of the bladder; and, ⅛th, the umbilical sheath (vagina umbilicalis). In the early period of uterine life, it also contains part of the intestinal canal, the vesicula umbilicalis either partly or wholly, and the omphalo-mesenteric vessels. Of these parts the umbilical veins and arteries, by their connection with the placenta, are the most important. The others our limits allow us merely to indicate.

The placenta is a round or orbicular, thick, cake-shaped mass, with two surfaces, a filamento-vascular, attached to the inner surface of the womb, and a smooth membranous one, to which the umbilical chord is fixed. It consists of lobular portions (cotyledones), separable from each other, and each of which receives a small artery derived from the uterine trunks, which are much enlarged during pregnancy. The average weight of the placenta is 1 pound 2 ounces.

The placenta, according to Dr Hunter (Anatomical Description of the Human Gravid Uterus, edit, by Dr Baillie, Lond. 1794), consists of two portions; a foetal or umbilical, and a maternal or uterine part.

The foetal part is composed entirely of ramifications of the umbilical arteries and umbilical vein. These, dividing with extreme minuteness, are distributed to all parts of the placenta. The branches of the umbilical arteries finally terminate in the umbilical vein, and have no other termination: all the branches of the umbilical vein arise from the umbilical arteries, and have no other commencement.

The maternal part consists of a whitish-coloured substance, which is spread over the outer surface of the placenta in the form of a membrane, and sends off innumerable irregular processes, which pervade its substance as deep as its inner surface. These are everywhere so blended and entangled with the ramifications of the umbilical system, that it is impossible to discover the nature of their union. They are interwoven in such a manner, however, as to leave innumerable small vacuities or cells between them, which communicate freely with each other through the whole mass. The maternal part is full of large and small arteries and veins, none of which are derived from the vessels of the foetal part, but all from the arteries and veins of the uterus. All the arteries are serpentine, and much convoluted; the larger, when injected, arc almost of the size of crow-quills; and, after little or no ramification, they terminate abruptly in the cells already described. This is their only termination. The veins have frequent anastomoses, pass in a very slanting direction, and generally appear flattened; some of them are as large as a goose-quill, but many of them very small; and all arise abruptly from the cells of the placenta. This is their only commencement.

The umbilical arteries, which are branches of the hypogastric, ascend beside the bladder and before the rectum, approach each other, pass over the fundus of the bladder, and reach the navel with the urachus. There they alter their direction, and are wound round the umbilical vein, which proceeds from the placenta by the same aperture (the naveD by which the arteries escape. These arteries, which are almost equal in diameter to the hypogastric or posterior iliac, of which they appear to be the continuation, diminish in size after birth, and appear then to be mere branches. Eventually they are obliterated and converted into solid chords, about 1⅜ inch from their origin.

The umbilical vein, which is larger than both arteries taken together, is the common trunk of the veins of the [7:2:828]placenta, from which it proceeds through the umbilical opening or navel, in the folds of the falciform ligament, to the umbilical fossa of the liver, where it divides into two branches, one large, proceeding to the vena portae and liver, another small, into the vena cava, known by the name of venous duct or canal (ductus venosus). The umbilical vein is distributed chiefly to the left lobe of the liver.

The structure of the foetus differs in many respects from that of the adult; and these differences depend on the stage which the process of developement has attained. As it is impossible to trace the history of this interesting process within the limits of this sketch, we shall merely specify the principal anatomical peculiarities by which the foetus is distinguished from the full-grown subject.

A large vascular body, denominated the thymus gland, is found to occupy the anterior mediastinum. The kidneys are covered by triangular filamento-vascular bodies, named renal capsules, larger than the glands themselves, and supplied with large blood-vessels. The liver is very large, especially its left lobe, and occupies not only the right hypochondriac and epigastric, but the left hypochondriac region. The lungs are compact and of a deep red colour, and sink in water; and the bronchial tubes are collapsed and void of air. In the heart the right and left auricle communicate freely by an oval aperture in the septum. The pulmonary artery, rising from the right ventricle, divides, not into two, as in the adult, but into three branches; one on each side, going to each lung, small, and conveying little blood; and one in the middle, proceeding to the aorta, about 9 lines long, named the arterial canal (ductus vel canalis arteriosus). The umbilical vein, proceeding to the liver, is distributed by about 15 or 20 branches to the left lobe of that organ. In the horizontal furrow it divides into two branches, one of which goes to the portal vein, the other, apparently the continuation of the trunk, opens into the vena cava, under the name of venous duct (ductus vel canalis venosus), forming with it an angle acute above, and provided with a valve. The kidneys consist of lobules as numerous as their tubular cones, which indeed these lobules are, separate from each other. The urinary bladder is not within the pelvis, but in the abdominal part of that cavity; and it terminates above in a point, to which a ligamentous process (urachus), connecting it to the navel, is attached. In the male, the testicles are contained in the abdomen, often immediately behind the internal aperture. Lastly, till the seventh month the pupillary aperture is closed by a peculiar membrane.

In the foregoing account of the anatomy of the human body, many points have been treated in a manner too short and cursory, considering their importance; and in the attempt to restrain it within due limits, the heads of several have been only indicated. For those who wish to study the subject more minutely, besides the works occasionally mentioned, we refer to the following general systems.

1. S. Th. Soemmering De Corporis Humani Fabrica ; Latio donata, ab ipso auctore aucta et emendata. Tom. i. De Ossibus, Trajecti ad Moenum, 1794. Tom. ii. De Ligamentis Ossium, 1794. Tom. iii. De Musculis, Tendinibus, et Bursis Mucosis, 1796. Tom. iv. De Cerebro et Nervis, 1798. Tom. v. De Angiologia, 1800. Tom. vi. De Splanchnologia, 1801. This work, which is excellent so far as it goes, and is particularly distinguished for clear arrangement, and distinctness, precision, and accuracy of description, is incomplete. It wants the anatomical description of the eye, the ear, and the generative organs in the two sexes. The first two defects, however, are ably supplied by the author in his Abbildungen des Menschlichen Auges, fol. Frankfort, 1801; and Abbildungen des Menschlichen Hoerorganes, fol. Frank. 1806.

2. Traite d' Anatomie Descriptive; par Xav. Bichat, Médicin du Grand Hospice d’Humanité de Paris, Professeur d’Anatomie et de Physiologie. Tome i. à Paris, 1801; tome ii. et iii. 1802; tome iv. par M. F. R. Buisson, 1803; tome v. par Philib. Jos. Roux, Prof. d’Anatomie, 1803. The death of the author interrupted the publication of this work in the middle of the third volume, the first part of which only is by Bichat; while the sequel of that volume is compiled from the materials left at his death. This constitutes the most accurate descriptive system yet extant; and the strongest proof of its superiority is, that its descriptive portion has been very closely copied in the work of Cloquet.

3. Cours d’ Anatomie Medicale, ou Element de l’ Anatomie de l’H omme, avec des Remarques Physiologiques et Pathologiques, et les Résultats de l' Observation sur le Siège et la Nature des Maladies, d’après l' Ouverture des Corps; par Antoine Portal, Prof. de Méd. &c. &c. Paris, 1803, tomes cinq. A complete and accurate work.

4. Grundriss der Anatomie des. Menschlichen Körpers, von J. C. Rosenmüller. Jena, 1806.

5. Handbuch der Menschlichen Anatomie, von J.F. Meckel, band i. ii. and iii. Halle und Berlin, 1815. This has been translated into French by MM. Jourdan and Breschet.

6. Traité d’Anatomie Descriptive, redig é d’après l’ordre adopté a la Faculté de M é dicine de Paris; par Hippol. Cloquet, Docteur en M é dicine, &c. This is a very good system of descriptive anatomy. In arrangement, Μ. Cloquet follows that of Bichat; and in description the first volume, and a great part of the second, are copied almost literally from the first, second, and part of the third of that author. It would have been quite as well had this been avowed; for it deprives Bichat of much of his most unquestionable merit, and gives an unfavourable impression of the candour of Μ. Cloquet. In the sequel of the second, on the vascular system, and the organs of respiration and digestion, the author has availed himself of the materials of Soemmering.

7. Elements of the Anatomy of the Human Body in its sound state, with occasional remarks on Physiology, Pathology, and Surgery, by Alexander Monro, Μ. D. &c. 2 vols. Edinburgh, 1825.

On the subject of General Anatomy, and several details on the anatomical divisions and peculiarities of the brain, we here beg to refer in general to a work already mentioned, viz.

8. Elements of General and Pathological Anatomy, adapted to the present state of knowledge in that science, by David Craigie, Μ. D. Edinburgh, 1828.

The engravings with which the foregoing article is illustrated have been sufficiently explained by literal or numeral references, in the course of description. We have only to add, that fig. 1 and 2 of Plate XXX., from Soemmering, are intended to show the important parts at the lower surface of the brain; fig. 3, from the same, the relations of the middle band, vault, and septum ; and the other two, from Reil, the internal arrangement of the nucleus. Plate XXXI., from Scarpa, shows the phrenic nerve, and the thoracic part of the pneumogastric and sympathetic, with the cardiac plexus and nerves. Plate XXXII., from Cruikshank, gives a general view of the arrangement of the lymphatics.
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