# Some distinctive characters of human structure

William Turner

► To cite this version:

William Turner. Some distinctive characters of human structure: address to the anthropological section. Report of the British association for the advancement of sciences, 1897, pp.21. hal-03554718

HAL Id: hal-03554718

https://hal.science/hal-03554718

Submitted on 3 Feb 2022

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>
<figure><img src="image_2.png" /></figure>

British Association for the Advancement of
Science.

<figure><img src="image_3.png" /></figure>

TORONTO, 1897.

<figure><img src="image_4.png" /></figure>

ADDRESS

TO THE

P. 186.

ANTHROPOLOGICAL SECTION.

BY

PROFESSOR SIR WILLIAM TURNER, M.B., LL.D., D.C.L., D.Sc.,
F.R.SS. L. and E.,

PRESIDENT OF THE SECTION.

Some Distinctive Characters of Human Structure.

WHEN the British Association for the Advancement of Science held its first Canadian meeting at Montreal in 1884, the subject of Anthropology, or the Science of Man, attained on that occasion for the first time the rank of an independent Section.

It was presided over by the accomplished writer and learned anthropologist Dr. E. B. Tylor, who selected as the subject-matter of his opening address several prominent questions in Anthropology, with special reference to their American aspects. For example, the question of the presence of a stone age in America; whether the aborigines are the descendants and representatives of man of the post-glacial period; the question of the Asiatic origin of the American Indians, and the arguments derived from anatomical structure, language, and social framework, bearing upon this theory. The traces of Asiatic influence in the picture writings of the Aztecs, correspondences in the calendar cycles of Mexico and Central America with those of Eastern Asia, and the common use of certain games of chance were also referred to.

It is not my intention, even had I possessed the requisite knowledge, to enlarge on the topics so ably discussed by my eminent predecessor. As my own studies have been more especially directed to the physical side of Anthropology, rather than to its archæological, historical, philological, moral and social departments, I naturally prefer to call your attention to those aspects of the subject which have from time to time come within the range of my personal cognizance. I have selected as the subject of my address 'Some Distinctive Characters of Human Structure.'

When we look at man and contrast his form and appearance with other vertebrate creatures, the first thing probably to strike us is his capability of assuming an attitude, which we distinguish by the distinctive term, the erect attitude. In this position the head is balanced on the summit of the spine, the lower limbs are elongated into two columns of support for standing on two feet, or for walking, so that man's body is perpendicular to the surface on which he stands or moves, and his mode of progression is bipedal. As a consequence of this, two of his limbs, the arms, are liberated from locomotor functions; they acquire great freedom and range of movement at the shoulder-joint, as well as considerable movement at the elbow and between the two bones of the forearm; the hands also are modified to serve as organs of prehension, which minister to the purposes of his higher intelligence. The erect position constitutes a striking contrast to the attitude
assumed by fish, amphibia, and reptiles when at rest or moving, in which vertebrates the body is horizontal and more or less parallel to the surface on which they move. Birds, although far removed from the erect attitude, yet show a closer approximation to it than the lower vertebrates or even the quadrupedal mammals. But of all vertebrates, those which most nearly approximate to man in the position assumed by the body when standing and walking are the higher apes.

The various adaptations of structure in the trunk, limbs, head, and brain which conduce to give man this characteristic attitude are essential parts of his bodily organisation, and constitute the structural test which one employs in answering the question whether a particular organism is or is not human.

These adaptations of parts are not mere random arrangements, made at hazard and without a common purpose; but are correlated and harmonised so as to produce a being capable of taking a distinctive position in the universe, superior to that which any other organism can possibly assume. If we could imagine a fish, a reptile, or a quadruped to be provided with as highly developed a brain as man possesses, the horizontal attitude of these animals would effectually impede its full and proper use, so that it would be of but little advantage to them. It is essential, therefore, for the discharge of the higher faculties of man, that the human brain should be conjoined with the erect attitude of the body. The passage of a vertebrate organism from the horizontal position, say of a fish, in which the back, with its contained spinal column, is uppermost, and the head is in front, to the vertical or erect position of a man, in which the back, with its contained spinal column, is behind, and the head is uppermost, may be taken as expressing the full range and limit of evolution, so far as the attitude is concerned, of which such an organism is capable. Any further revolution of the body, as in the backward direction, would throw the back downwards, the head backwards, and would constitute a degradation. It would not be an advance in the adaptation of structure to the duties to be discharged, but rather an approach to the relation of parts existing so generally in invertebrate organisms.

At an early period in the evolution of the human mind and intelligence an anthropomorphic conception of the Deity arose, to whom were ascribed the possession of the bodily form and attitude of man, and even human affections and passions. This idea took so firm possession of the imagination that, in the course of time, it obtained objective expression in the statues of ancient Greece and Rome and in the masterpieces of Christian art. In one of the most ancient of all books, in which is embodied the conception entertained by the Jewish writers of the Genesis of the world, and of all creatures that have life, we read that 'God created man in his own image, in the image of God created he him, male and female created he them.' By the association, therefore, of the human form with the idea of Deity, there was naturally present in the minds of these writers, although not expressed in precise anatomical language, a full recognition of the dignity of the human body, of its superiority to that of all other creatures, and that the human form was the crown and glory of all organic nature.

This conception of the dignity of man in nature is not confined to those writings which we are accustomed to call sacred. The immortal Greek philosopher and naturalist, Aristotle, in his treatise 'On the Parts of Animals,' composed at least three hundred years B.C., refers more than once to the erect attitude of man, and associates it with his 'God-like nature and God-like essence.' In the second century of our present era lived another Greek author, Claudius Galen, whose writings exercised for many centuries a dominating influence in medicine and anatomy, comparable to that wielded by Aristotle in philosophy. Although Galen, as has been shown by Vesalius and other subsequent anatomists, was often incorrect in his descriptions of the internal parts of the human body, doubtless because his opportunities of dissection were so scanty, he had attained a correct conception of the perfection of its external form, and he thoroughly understood that in its construction it was admirably fitted for the sentient and intelligent principle which animated it, and of which it was merely the organ. In his treatise on the use of the various parts of the body he associates the hand with the exercise of the gift

of reason in man, and he speaks of it as an instrument applicable to every art and occasion, as well of peace as of war. It is, he says, the best constructed of all prehensile organs, and he gives a careful description of how both the hand as a whole and the individual digits, more especially the thumb, are brought into use in the act of grasping.<fnref n="1" /> Galen does not indeed enter into the minute anatomical details which have been emphasised by more recent writers on the subject, but by none of these has the use of the hand and its association with man's higher intelligence been more clearly and more eloquently expressed than by the Greek physician and philosopher seventeen centuries ago.

By the publication in 1850 of Charles Darwin's ever-memorable treatise 'On the Origin of Species,' an enormous impulse was given to the study of the anatomy of man in comparison with the lower animals, more especially with the apes. By many anatomists the study was pursued with the view of pointing out the resemblances in structure between men and apes; by a more limited number to show wherein they did not correspond. I well remember a course of lectures on the comparative characters of man delivered thirty-five years ago by my old master, Professor John Goodsir, in which, when speaking of the hand of man and apes, he dwelt upon sundry features of difference between them.<fnref n="2" /> The human hand, he said, is the only one which possesses a thumb capable of a free and complete movement of opposition. It may be hollowed into a cup and it can grasp a sphere. It is an instrument of manipulation co-extensive with human activity. The ape's hand again is an imperfect hand, with a short and feeble thumb, and with other clearly defined points of difference and inferiority to that of man. It can embrace a cylinder, as the branch of a tree, and is principally subservient to the arboreal habits of the animal. Its fingers grasp the cylinder in a series of spirals.

Here then is an important difference in the manipulative arrangements of the two hands, the advantage being with the hand of man, in regard to the greater variety of movement and adaptability, to co-ordinate it with his reasoning faculties. As showing the acuteness of perception of Galen and his complete recognition of a fundamental feature of the human hand, he also dwells on the hand being able to form a circle around a sphere, so as to grasp it on every side, and to touch it with every part of itself, whilst it can also securely hold objects that possess plane or concave surfaces. So impressed was the old Greek writer with the fitness of the hand to discharge the duties imposed on it by the higher intelligence of man that, pagan though he was, he regarded its construction as evidence of design in nature, and as a sincere hymn to the praise and honour of the Deity.

It is not my intention to dwell upon the multitudinous details of those features of structure which distinguish man from other vertebrates, for these have been considered and described by numerous writers. The leading structural differences constitute the merest commonplaces of the human anatomist, and are already sufficiently imprinted on the popular mind. But it may not be out of place to refer to certain aspects of the subject which are not so generally known, and the significance of which has been brought into greater prominence by recent researches.

If we compare the new-born infant with the young of vertebrates generally, we find a striking difference in its capability of immediately assuming the characteristic attitude of the species. A fish takes its natural posture and moves freely in its element as soon as it is hatched. A chicken can stand and walk when it is liberated from the egg, though, from its wings not being developed, it is not at once able to fly. A lamb or calf can assume the quadrupedal position a few minutes after its birth. But, as we all know, the infant is the most helpless of all young vertebrates, and is months before it can stand on two feet and move freely on them. During the period of transition,

<footnote n="1">¹ See passages translated in Dr Kidd's *Bridgewater Treatise*, 1833, and Dr J. Finlayson's *Essay on Galen*, Glasgow, 1895.</footnote>

<footnote n="2">² 'On the Dignity of the Human Body,' in *Anatomical Memoirs*, by John Goodsir, vol. i. p. 238, Edinburgh, 1868.</footnote>
from the stage of absolute dependence on others to the acquisition of the power of bipedal progression, important modifications in the structural arrangements both of the spine and lower limbs have to take place. At the time of birth the infant's spinal column exhibits only two curves; one, corresponding to the true vertebrae, extends from the upper end of the neck to the lowest lumbar vertebra, and the concavity of its curve is directed forwards; the other and shorter corresponds to number and character of the curves, the new-born infant differs materially from the adult man, in whose spine, instead of one continuous curve from the neck to neck, succeeded by one concave forwards in the region of the which again is succeeded by a marked convexity forwards in the vertebrae of the new-born child. The formation and preservation of this alternating series of the lumbar convexity is correlated with the straightening of the lower limbs when the child begins to walk.<fnref n="1" />

When the child is born, the curvature of its spine in the dorso-lumbar region approximates to that of an ordinary quadruped in which there is no lumbar convolutions. For some time after its birth the infant retains one continuous curve concave character of the spinal curve in the dorso-lumbar region, and, as it acquires nervous gression in the early months by creeping on hands and knees approximates to that months that it can erect its trunk, completely extend the hip and knee joints, and enables it to stand or move about on two feet. Hence there is this great difference born with the dorso-lumbar curve proper to its attitude, and which it retains after its birth, the characteristic spinal curves of the man. These curves are therefore secondary in their production; they are acquired after birth, and are not acquiring them at the proper time is a fundamental attribute of the human organism.<fnref n="2" />

It has sometimes been assumed that the acquisition of the erect attitude by the young child is due to the fostering care of the mother or nurse; that it is a matter of training, encouragement and education, without which the child would not raise itself upon its feet. I cannot, however, agree with this opinion. If one fitted for its nutrition and growth, it should never receive any aid or instruction in its mode of progression, there can, I think, be little doubt that when it had gained sufficient strength it would of itself acquire the erect attitude. The greater growth in length of the lower limbs, as compared with the upper, would render it inconvenient to retain the creeping or the quadrupedal position.

We cannot lose sight of the important influence which, altogether independent of education, is exercised by parents on their offspring. The transmission of hereditary qualities, through the germ from which each individual organism is derived, is one of the fundamental and most striking properties of the germ plasm. Characters and peculiarities which appertain not only to the family of which the individual is a member, but also to the species to which he belongs, are conveyed through it from one generation to another. Hence, as the capability of assuming the erect attitude and of thus standing and moving on two feet have been attri-

butes of the human form from its beginning, there can be little doubt that this power is potential in the human organism at the time of birth, and only requires a further development of the nervous and muscular systems to become a reality, without the aid of any special training.

The spinal column in the region of the true vertebrae consists of numerous bones jointed together, and with discs of soft fibro-cartilage interposed between and connecting the bodies of adjoining vertebrae with each other. It is to their presence that the spinal column owes its flexibility and elasticity. These discs are larger and thicker in the region of the loins, where the lumbar convexity is situated, than in other parts of the column, and there can be no doubt that the acquisition of this convexity is intimately associated with the presence of these discs.

It is a matter for observation and consideration to what extent the bodies of the vertebrae contribute to the production of this curve. A few years ago Professor Cunningham, of Dublin,<fnref n="1" /> and ¹² undertook much about the same time researches into the form and dimensions of the bodies of these bones. Our observations were made independently of each other and on two different series of skeletons, and as we arrived at practically the same conclusions, we may, I think, infer that, in their main features at least, these conclusions are correct.

The method followed in the investigation was to measure the diameter from above downwards of the body of each of the five lumbar vertebrae, both in front and behind. If the upper and lower surfaces of the bodies of the vertebrae were parallel to each other, it is obvious that, so far as they are concerned, the column formed by them would be straight, as is the case in a column built of hewn stones possessing similar parallel surfaces. But if the surfaces are not parallel the body of the vertebra is wedge-shaped; should the front of the collective series of bones have a greater vertical diameter than the back, it is equally obvious that the column would not be straight, but curved, and with the convexity forwards. From the examination of a considerable number of spinal columns of Europeans, we found that, although the vertical diameter of the bodies of the two highest vertebrae was greater behind than in front, in the two lowest the anterior vertical diameter so greatly preponderated over the posterior that the anterior vertical diameter of the bodies of the entire series of lumbar vertebrae in each spine was collectively greater than the corresponding diameter of the posterior surface. In twelve European skeletons I observed that the mean difference was between 5 and 6 mm. in favour of the anterior surface. If we are to regard the collective vertical diameter anteriorly of the five bones as equal to 100, the same diameter posteriorly is only equal to 96, which may be regarded as the lumbar index in Europeans. Dr. Cunningham obtained a similar index from the examination of a much larger number of European skeletons, and he further showed that in women the lumbar convexity forwards is more pronounced than in men. It follows therefore, from these observations, that when the broad end of the wedge-shaped bodies is in front the bones themselves would by their form give a forward convexity to the spine in the lumbar region. But a similar wedge-shaped form is also possessed by the lower intervertebral discs in this region, and especially by that interposed between the last lumbar vertebra and the sacrum. Hence it follows that both vertebral bodies and intervertebral discs contribute in the white races to the production of the lumbar convexity.

When we pass to the examination of the corresponding region in the spines of those races of men that we are accustomed to call lower races, we find a remarkable and important difference. Let us take as a characteristic example of a lower race the aborigines of Australia. In their skeletons our observations have proved, that the vertical diameter of the bodies of the five lumbar vertebrae was collectively deeper behind than in front. In my series of skeletons the mean difference was between 6 and 7 mm. in favour of the posterior surface, so that they possessed the opposite condition to that which prevails in Europeans. Hence if the spine had

<footnote n="1">¹ Professor Cleland, in *Reports of British Association*, 1863, p. 112.</footnote>

<footnote n="2">² In his work on the *Origin and Progress of Language* (vol. i. p. 173, Edinburgh, like speech, is acquired with difficulty and as the result of training.</footnote>

<footnote n="1">¹ The Lumbar Curve in Man and the Apes,' Cunningham, *Memoirs of the Royal Irish Academy*, Dublin, 1886.</footnote>

<footnote n="2">² Report on Human Skeletons,' *Challenger Reports*, Part XLVII., 1886.</footnote>
been constructed of vertebrae only, instead of a lumbar convexity, the column would have possessed a forward concavity in that region. For this character, as shown in the skeleton only, I have suggested the descriptive term 'Koilorachic.'

We know, however, that elastic discs are intercalated between the bodies of the osseous vertebrae in the black races as well as in Europeans. It is necessary, therefore, to examine their spinal columns, when the intervertebral discs are in position, in order to obtain a proper conception of the character of the curve in the living man.

A few years ago Professor Cunningham had the opportunity of studying the spinal column of an aboriginal Australian,<fnref n="1" /> in which the intervertebral discs had been preserved in their proper position, in relation to the bones, without losing their flexibility, or their natural shape and thickness. He found that, whilst the bodies of the lumbar vertebrae were longer than in Europeans, the proportion of intervertebral disc to vertebral body was distinctly less, so that the disc appeared to be reduced in depth, in relation to the greater vertical diameter of the vertebral body. Notwithstanding this difference, as compared with the white man, the Australian spine had a marked lumbar convexity which showed no material difference from that seen in Europeans. As the lumbar curve was not due to the wedge-shaped form of the bodies of the vertebrae, it was therefore produced solely by the strong wedge-shape of the intervertebral discs, and was not, as in Europeans, a product of a combination of both these factors. The spinal column, when complete, is not therefore koilorachic in the lumbar region.

The greater vertical diameter of the bodies of the lumbar vertebrae behind than in front, as compared with Europeans, is not limited to the Australians, but is participated in by other black races, as the now extinct Tasmanians, the Bushmen, Andaman Islanders, and Negroes, which, if tested solely by the measurements of the skeleton, would also be koilorachic. But in these races intervertebral discs are also present, and there can be no doubt that through the compensating influence of the wedge-shaped discs, with their deeper ends in front, the lumbar curve is in them also convex forwards. It is clear, therefore, that in the black races the intervertebral discs play relatively a more important part in the production of the lumbar curve than in Europeans.

One of the requirements of civilisation is the wearing of clothes, and fashion frequently prescribes that they should be tight-fitting and calculated to restrict motion in and about the spinal column. In savage races, on the other hand, clothing is often reduced to a minimum, and when worn is so loose and easy as in no way to hamper the movements of the body. The spinal column retains therefore in them much more flexibility, and permits the greater measure of freedom in the movements of the trunk, which is found in savage man, and has often been referred to by travellers.

It used to be considered that the possession of a lumbar convexity in the spinal column was the exclusive privilege of man, and was shared in by no other vertebrae. There can be no doubt that it attains a marked development in the human spine, and as such is associated with the erect posture. But the observations of Cunningham on the spinal column of apes, more especially the anthropoid group, made in fresh specimens, in which the intervertebral discs were in place, have proved that in the Chimpanzee the lumbar convexity is probably as strongly pronounced as in the adult man. In a Chimpanzee, two years old, the development is more advanced that in a child of the same age. The lumbar convexity is established at an earlier age than in the child, for it would seem as if the Chimpanzee attained its maturity at a younger period of life than the human being. In the Orang the lumbar curve is more feeble than in Man and the Chimpanzee, and in the specimen described by Cunningham resembled that of a boy six years old. In a fresh specimen of the Gibbon, examined by the same anatomist, the lumbar curve was intermediate between the Chimpanzee and the Orang.

In 1888, I purchased the bones of an adult male Gorilla, in which the vertebrae

were in position and connected together by the dried intervertebral discs. This condition is of course not so satisfactory, for the study of the spinal curves, as if the specimen had been fresh, and with the discs retaining their natural flexibility and elasticity. But it was quite obvious that the spine possessed an alternating series of convex-concave curves from above downwards. The cervical and lumbar convexities, more especially the latter, did not project so far forwards as in man, and the dorsal concavity was not so deep. The most projecting part of the lumbar convexity was at the junction of the bodies of the third and fourth lumbar vertebrae and their intermediate disc. A vertical line drawn downwards from the most prominent part of this convexity fell in front of the coccyx. When prolonged upwards it passed in front of the bodies of the dorsal vertebrae, and intersected the body of the sixth cervical vertebra, so that the bodies of the vertebrae, higher than the sixth, were directed obliquely from below upwards and forwards in front of the vertical line.

The dried state of the discs did not enable one to determine precisely the proportion in which they entered into the formation of the length of the column, but the vertical diameter of the interlumbar and lumbo-sacral discs was obviously not as great as in the human spine. On the other hand, the vertical diameter of the bodies of the lumbar vertebrae was greater than in man, so that the length of the lumbar spine, and possibly its degree of convexity, were due more to the bodies of the vertebrae than to the elastic discs interposed between them. The Gorilla corresponds with the Chimpanzee in having longer vertebral bodies and shorter intervertebral discs than in man.

Without going into the question whether a lumbar convexity exists in the tailed monkeys, the determination of which with precision is a matter of some difficulty, it must be obvious that the presence of this convexity can no longer be regarded as the exclusive prerogative of man. It undoubtedly forms an important factor in the study of the erect attitude; but in order that man should acquire and be able to retain his distinctive posture, something more is necessary than the possession of a spinal column with a curve in the lumbar region convex forwards.

Our attention should now be directed to the lower limbs, more especially to the two segments of the shaft, which we call thigh and leg.

If we look at a quadruped we see that the thigh is bent on the trunk at the hip joint, and that the leg is bent on the thigh at the knee joint; whilst the foot forms more or less of an angle with the leg, and the animal walks either on the soles of its feet or on its toes. In the Anthropoid apes there is also distinct flexure both of the hip and knee joints, so that the leg and thigh are set at an angle to each other, and the foot is modified, through a special development of the great toe, into an organ of prehension as well as of support. When we turn to the human body we find that in standing erect the leg and thigh are not set at an angle to each other, but that the leg is in line with and immediately below the thigh, that both hip and knee joints are fully extended, so that the axis of the shaft of the lower limb is practically continuous with the axis of the spine. The foot is set at right angles to the leg, and the sole is in relation to the ground. The vertical axis of the shaft of the lower limb, the extended condition of the hip and knee joints, and the rectangular position of the foot to the leg are therefore fundamental to the attainment of the erect attitude of man.

In narratives of travel by those who have studied the Penguins in their native habitats, you may read that these birds may be seen standing on the rocks on the coasts which they frequent, in rows like regiments of soldiers, and the idea has become implanted in the minds of many that they can stand erect. Even so accomplished a writer and acute a critic as the late Mr. G. H. Lewes thought that the Penguins had the vertical attitude when standing, and that some mammals, as the Jerboa and Kangaroo, very closely approached to it. The attitude of man was, he considered, merely a question of degree, and did not express a cardinal distinction.<fnref n="1" />

In arriving at this conclusion, however, only the external appearance of the birds and mammals referred to by him can have been looked at. If the skin and

<footnote n="1">¹ Proc. Roy. Soc. London, January 24, 1889, vol. xlv.; also see *Journal of Anatomy and Physiology*, vol. xxiv. 1890.</footnote>

<footnote n="1">¹ Aristotle, *A Chapter from the History of Science*, p. 303, London, 1861.</footnote>
flesh be removed, and the arrangement of the constituent parts of the skeleton be studied, it will be seen that the axis of the spine in them, instead of being vertical, is oblique, and that there is no proper lumbar convexity; that the hip and knee joints, so far from being extended, are bent; that the thigh is not in the axis of the spine, and that the leg, instead of being in a vertical line with the thigh, is set at an acute angle to it. The so-called vertical attitude therefore in these animals is altogether deceptive. It does not approximate to, and can in no sense be looked upon as equivalent to, the erect attitude in man.

We may now consider what agents come into operation in changing the curve of the spine from the concavity forwards, found in the new-born infant, to the alternating series of curves so characteristic of the adult. The production of the lumbar convexity is, without doubt, due to structures associated with the spine, the pelvis and the lower limbs, whilst the cervical convexity is due to structures acting on the spine and the head.

There can, I think, be little doubt that muscular action plays a large part in the production of the cervical and lumbar convexities. The study of the muscles, associated with and connected to the spinal column, shows that large symmetrically arranged muscles, many of which are attached to the neural arches and transverse processes of the vertebrae, extend longitudinally along the back of the spine, and some of them reach the head. On the other hand, those muscles which lie in front of the spine, and are attached to the vertebrae, are few in number, and are practically limited to the cervical and lumbar regions, in which the spine acquires a convexity forwards.

It has already been pointed out that the formation of the lumbar convexity is correlated with the power of extending the hip joints and straightening the lower limbs. When these joints are in the position of extension, an important pair of muscles called the 'psœæ,' which reach from the small trochanter of the femur to the bodies and transverse processes of the lumbar vertebrae, are in a state of tension. In the act of extending the hip joints so as to raise the body to the erect position, the opposite ends of these muscles are drawn asunder, and the muscles are stretched and elongated, so that they necessarily exercise traction upon the lumbar spine. Owing to its flexibility and elasticity, a forward convexity is in course of time produced in it in this region. By repeated efforts the convexity becomes fixed and assumes its specific character.

Along with the changes in the spinal column, a modification also takes place in the inclination of the pelvis during the extension of the hip joints and the straightening of the lower limbs. The muscle called 'iliacus' is conjoined with the psœæ at its attachment to the small trochanter, but instead of being connected to the spinal column by its upper end, it is attached to the anterior surface of the ilium. It exercises traction therefore on that bone, draws it forwards and increases the obliquity of the pelvic brim. This in its turn will react on the lumbar spine and assist in fixing its convexity.

By some anatomists great importance has been given to the 'ilio-femoral band,' situated in the anterior part of the capsular ligament of the hip joint, as causing the inclination of the pelvis, and in promoting the lumbar curve. This band is attached by its opposite ends to the femur and the ilium. As the hip joint is being extended, the ends are drawn further apart, the band is made tense, and the ilium might in consequence be drawn upon, so as to affect the inclination of the pelvis. As the ligament has no attachment to the spinal column, it cannot draw directly on it, but could only affect it indirectly through its iliac connections. It can therefore, I think, play only a subordinate part in the production of the lumbar curve.

Contemporaneous with the straightening of the lower limbs and the extension of the hip joints, the spinal column itself is elevated by muscles of the back, named 'erectores spinæ,' which, taking their fixed points below, draw upon the vertebrae and ribs and erect the spine. The lumbar convexity is the form of stable equilibrium which the flexible spinal column tends to take under the action of the muscular forces which pull upon it in front and behind. It is probably due to the fact that the average pull, per unit of length, of the psœæ muscles attached in

front is greater than the average pull, per unit of length, of the muscles attached behind in the same region.

The muscles which lie on the back of the neck and which are attached to the occipital part of the skull, when brought into action, will necessarily affect the position of the head. The new-born infant has no power to raise the head, which is bent forward, so that the chin is approximated to the chest. As it acquires strength the head becomes raised by the muscles of the back of the neck, and the flexible spine in the cervical region loses its primary curve, concave forwards, and gradually assumes the cervical convexity. The formation of this curve is, I believe, assisted by the anterior recti muscles, the lower ends of which are attached to the front of the vertebrae, whilst their upper ends are connected to the basi-occipital. In the elevation of the head the opposite ends of the muscles are drawn apart, which would exercise a forward traction upon the cervical vertebrae. The production of the cervical convexity precedes the formation of the lumbar curve, for an infant can raise its head, and take notice of surrounding objects, months before it can stand upon its feet.

We shall now look at the bones in the thigh and leg, which possess characters that are distinctively human, and which are associated with the erect posture. These characters can be more clearly r-cognised when the bones are contrasted with the corresponding bones of the large Anthropoid apes.

As compared with the ape, the shaft of the human thigh bone is not so broad in relation to its length; when standing erect the shaft is somewhat more oblique, it is more convex forwards and generally more finely modelled, and it has three almost equal surfaces, the anterior of which is convex. But, further, a strong ridge (linea aspera) extends vertically down its posterior surface; so that a section through the shaft is triangular, with the two anterior angles rounded and the posterior prominent. In the Gorilla, Chimpanzee, and Orang, the shaft is flattened from before backwards, and the linea aspera is represented by two faint lines, separated from each other by an intermediate narrow area. A section through the shaft approximates to an ellipse. In the Gibbon the femur is greatly elongated, and the shaft is smooth and cylindriform. The linea aspera is for the attachment of powerful muscles, which are more closely aggregated in man than in apes, so that the human thigh possesses more graceful contours.

In the human femur the shaft is separated from the neck by a strong anterior intertrochanteric ridge, to which is attached the ilio-femoral ligament of the hip joint, which, by its strength and tension, plays so important a part in keeping the joint extended when the body is erect. In the Anthropoid apes this ridge is faint in the Gorilla, and scarcely recognisable in the Orang, Gibbon, and Chimpanzee. and the ilio-femoral ligament in them is comparatively feeble. It may safely therefore be inferred that in apes, with their semi-erect, crouching attitude, the ilio-femoral band is not subjected to, or capable of sustaining, the same strain as in man.

The head of the thigh bone is also distinctive. In the apes the surface covered by cartilage is approximately a sphere, and is considerably more than a hemi-sphere. It is sharply differentiated from the neck by a definite boundary, and it has a mushroom-like shape. In man the major part of the head is also approximately a sphere; but, in addition, there is an extension outwards of the articular area on the anterior surface and upper border of the neck of the bone. The form of this extended area differs from the spherical shape of the head in general. The curvature of a normal section of its surface has a much larger radius than the curvature of a normal section of the head, near the attachment of the ligamentum teres.

The amount of this extended area varies in different femora, but as a rule it is larger and more strongly marked in Europeans than in the femora of some savages which I have examined. When the joint is in the erect attitude, the area is in contact with the back of the iliac part of the ilio-femoral ligament. It provides a cartilaginous surface which, during extension of the joint, is not situated in the acetabulum, but, owing to the centre of gravity falling behind the axis of movement, is pressed against that ligament, and contributes materially to its tension. It is associated with the characteristic position of the human hip joint in
standing, and may be called appropriately the extensor area. When the femur is abducted it passes within the acetabulum. The head of the femur in man is not so sharply differentiated from the neck as in the Anthropoid apes, especially in the region of the extensor articular area.

Both man and apes possess at the lower end of the femur a trochlear or pulley-like sur ace in front for the patella, and two condyles for the tibia. In the apes the trochlea is shallow, and the concave curve from side to side is a segment of an approximate circle, with a large radius. In man the trochlea is much deeper, and the inner and outer parts of the curve deviate considerably from a circle, and are not symmetrical; the outer part is wider and extends higher on the front of the bone than the inner part, whilst the direction of the curve changes towards the edges of the trochlea.

In the apes the articular surface of the inner condyle is very markedly larger than that of the outer condyle, both in breadth and in the extent of its backward curve, which winds upwards on the posterior part of the condyle, so that the articular surface is continued on to its upper aspect. The curve of the outer condyle is much sharper, and the condyle does not project so far backwards; its articular surface is not prolonged so high on the back of the bone. In the apes, therefore, the inner is the more important condyle in the construction of the knee joint, and the marked extension of its articular area backwards and upwards is associated with the position and movements of the knee in flexion. In the apes the thigh is more rotated outwards than in man, and the inner condyle is directed to the front of the limb.

In man there is not nearly the same disproportion in the size of the two condyles as in the apes. I have occasionally seen in man the articular area of the inner broader than that of the outer condyle, but more usually the outer is appreciably the wider. The backward curve of the outer condyle is also prolonged somewhat higher than that of the inner, and thus the condition of the two condyles is the reverse of that found in the ape. It should, however, be stated, as has been shown by Dr. Havelock Charles,<fnref n="1" /> that in persons, who habitually rest in the squatting position, an upward extension of the articular area of the inner condyle exists, which is associated with the acute flexion of the knee whilst squatting. In man, the outer condyle, when seen in profile, is, as compared with the inner, more elongated antero-posteriorly than in the Gorilla. The approximate equality in the size of the two condyles in man is, without doubt, associated with the extension of the weight of the body downwards on the head of the tibia. In the ape in man; but it is wider behind in man than in the ape, for in the latter the inner condyle inclines nearer to the outer condyle than in man.

In man, when the knee joint is extended, the tibia is slightly rotated outwards on the femoral condyles, and the joint is fixed, partly by the tension of the lateral and posterior ligaments and the anterior crucial ligament, and partly by the genetic tension of the muscles and fasciae around the joint. So long as these structures remain tense, the joint cannot be bent, and no lateral movement, or rotation, is permitted. The fixation of the joint is of fundamental importance in the act of standing. Free rotation of the human knee can only take place when the joint is acutely bent.

In apes, the joint cannot be fully extended; its natural position, when the animal is standing, is partial flexion, and in this position a limited rotation is permitted, which can be greatly increased when the joint is more completely bent. In rotating the leg on the thigh the inner condyle is apparently the pivot. The ape to turn the sole inwards and forwards when holding an object. These movements produce results, which approximate to those occasioned by pronation and supination of the radius on the ulna, in the movements of the forearm and hand.

In the Anthropoid apes, the head of the tibia slopes very decidedly backwards at the upper end of the shaft, so that its axis forms an angle with that of the shaft,

<fnref n="1" /> *Journal of Anatomy and Physiology*, vol. xxviii.

and the head may be described as retroverted. If the shaft of the tibia were held vertically, the articular surface for the inner condyle would also slope downwards and backwards, and to a greater degree than that for the outer condyle. But in the natural semillexed position of the ape's knee the condylar articular surfaces of the tibia are essentially in the horizontal plane.

In the human tibia the axis of the head is, as a rule, almost in line with that of the shaft, and the backward and downward slope of the inner articular surface is not so great as in the ape. In some human tibiae, however, well-marked retroversion of the head has been seen. In skeletons referred to the Quaternary period of the geologist, this character has been noticed by MM. Collignon, Fraipont, and Testut, and the inference has been drawn that the men of that period could not extend the knee joint and walk as erect as modern man. It has, however, been shown by Professor Manouvrier<fnref n="1" /> and Dr. Havelock Charles<fnref n="2" /> that this condition of the tibia is not uncommon in some races of men, in whom there can be no question that the attitude is erect when standing. Dr. Charles has associated the production of retroversion to the habit in these races of resting on the ground in the position of squatting. I have found in the tibiae of the people of the Bronze Age that retroversion of the head of the tibia is not uncommon. In five specimens the backward slope of the head formed with the vertical axis of the shaft an angle which ranged in the several bones from 20° to 30°. But when these tibiae were put into the erect position alongside of similarly placed modern European bones, the condylar articular surfaces were seen to approximate to the horizontal plane in all the specimens. In order, therefore, that retroversion of the head of the tibia should be associated with inability to extend the knee joint, it is obvious that the articular surfaces should have a marked slope downwards and backwards, as is the case in the Anthropoid apes, when the shaft of the tibia is held in a vertical plane.

I shall now proceed to the examination of the human foot (pes), and in order to bring out more clearly its primary use as an organ of support and progression, I shall contrast it with the human hand (manus) and with the manus and pes in apes. In man, while standing erect, the arched sole of the foot is directed to the ground, and rests behind on the heel and in front on pads, placed below and in line with the metatarso-phalangeal joints, the most important of which is below the joint associated with the great toe. It is therefore a plantigrade foot. The great toe (hallux) lies parallel to the other toes, and from its size and restricted movements gives stability to the foot.

The ape's foot agrees with that of man in possessing similar bones and almost similar soft parts; but it differs materially as to the uses to which it can be put. Some apes can undoubtedly place the sole upon the ground, and in this position use the foot both for support and progression; though the Orang, and to some extent other Anthropoid apes, rest frequently upon the outer edge of the foot. But in addition these animals can use the foot as a prehensile organ like the hand. The old anatomist Tyson, in his description of a young Chimpanzee,<fnref n="3" /> spoke of the pes as ' liker a hand than a foot ' and introduced the term ' quadrumanous,' four-handed, to designate this character. This term was adopted by Cuvier and applied by him to apes generally, and has long been in popular use. The eminent French anatomist was, however, quite alive to the fact that though the pes was capable of being used as a hand, yet that it was morphologically a foot, so that the term was employed by him to express a physiological character.

In the ape, the great toe, instead of being parallel to the other toes as in man, is set at an angle to them, not unlike the relation which the thumb (pollex) bears to the fingers in the human hand. It is able, therefore, to throw the hallux across the surface of the sole in the prehensile movement of opposition. As it can at the same time bend the other toes towards the sole it also has the power of encircling an object more or less completely with them. By the joint action of

<figure><img src="image_5.png" /></figure>

<footnote n="1">¹ Mémoires de la Société d'Anthropologie de Paris, 1890.</footnote>

<footnote n="2">² *Journal of Anatomy and Physiology*, vol. xxviii.</footnote>

<footnote n="3">³ *Anatomy of a Pygmy*, 1899, p. 13.</footnote>
all the toes a powerful grasping organ is produced, more important even than its hand, in which the thumb is feebly developed.

It has sometimes been assumed that the human foot is also a prehensile instrument as well as an organ of support. In a limited sense objects can undoubtedly be grasped by the human toes when bent towards the sole. In savages, this power is preserved to an extent which is not possible in civilised man, in whom, owing to the cramping, and only too frequently the distorting influence, exercised by badly fitting boots and shoes, the proper development of the functional uses of the toes is impeded and their power of independent movement is often destroyed.

Even in savages who have never worn shoes, the power of grasping objects by the toes cannot be regarded as approximately equal in functional activity and usefulness to the range of movement possessed by the ape. The four outer toes are so short and comparatively feeble, that they cannot encircle an object of any magnitude. But, what is even more important, the great toe cannot be opposed to the surface of the sole, in the way that an ape can move its hallux or a man his thumb. Savage man can no doubt pick up an object from the ground with the great toe. Many of us have doubtless seen, among civilised men, persons who have had the misfortune to be born without arms, or who have accidentally lost them in early life, who have trained themselves to hold a pen, pencil, brush, or razor with the foot, and to write, draw, paint, or even shave. But in these cases the object is held between the hallux and the toe lying next to it, and not grasped between the great toe and the sole of the foot by a movement of opposition.

If we compare the anatomical structure of the human foot with that of the foot of the ape, though the bones, joints, and muscles are essentially the same in both, important differences in arrangement may be easily recognised, the value of which will be better appreciated by first glancing at the thumb. Both in man and apes the thumb is not tied to the index digit by an intermediate ligament, which, under the name of 'transverse metacarpal,' binds all the fingers together, and restricts their separation from each other in the transverse plane of the hand. The great toe of the ape, similarly, is not tied to the second toe by a 'transverse metatarsal ligament,' such as connects together and restricts the movements of its four outer toes in the transverse plane of the foot. The hallux of the ape is therefore set free. It can, like the thumb of man and ape, be thrown into the position of opposition and be used as a prehensile digit. Very different is the case in the human foot, in which the hallux is tied to the second toe by a continuation of the same transverse metatarsal ligament which ties the smaller toes together. Hence it is impossible to oppose the great toe to the surface of the sole in the way in which the thumb can be used, and the movements of the digit in the transverse plane of the foot are also greatly restricted.

The development of a connecting transverse band, for the restriction of the movements of the great toe in man, is not the only anatomical structure which differentiates it from the hallux of an ape, or the thumb in the hand. In the manus both of man and apes the joint between the metacarpal bone of the thumb and the bone of the wrist (trapezium) is concavo-convex, or saddle-shaped, and permits of a considerable range of movement in certain directions, and notably the movement of opposition. A joint of a similar configuration, permitting similar movements, is found in the pes of the ape between the metatarsal of the hallux and the tarsal bone with which it articulates. In the foot of man, on the other hand, the corresponding joint is not saddle-shaped, but is almost plane-surfaced, and consequently the range of movement is slight, and is little more than the gliding of one articular surface on the other.

One of the chief factors in the production of the movement of opposition in the manus of man and apes is a special muscle, the opponens pollicis, which, through its insertion into the shaft of the metacarpal bone of the thumb, draws the entire digit across the surface of the palm. In the foot of the Anthropoid apes there is not complete correspondence in different species in the arrangement of the muscles which move the great toe. In the Orang the abductor hallucis, in addition to the customary insertion into the phalanx, may give rise to two slips, one of which is inserted into the base and proximal part of the first metatarsal bone, and the other

into the radial border of its shaft for a limited distance; these slips apparently represent an imperfect opponens muscle, which acts along with the adductor and short flexor muscle of the great toe. In the other Anthropoid apes, the muscle seems to be altogether absent, and the power of opposition is exercised solely by the adductor and the flexor brevis hallucis, the inner head of the latter of which is remarkably well developed.<fnref n="1" /> In the human foot there is no opponens hallucis, and the short flexor of the great toe is, in relation to the size of that digit, comparatively feeble, so that no special provision is made for a movement of opposition.

The character and direction of the movements of the digits both in hand and foot are imprinted on the integument of palm and sole. In the palm of the human hand the oblique direction of the movements of the fingers towards the thumb, when bent in grasping an object, is shown by the obliquity of the two great grooves which cross the palm from the root of the index to the root of the little finger. The deep curved groove, extending to the wrist, which marks off the eminence of the ball of the thumb from the rest of the palm, is associated with the opponent action of the thumb, which is so marked in man that the tip of the thumb can be brought in contact with a large part of the palmar surface of the hand and fingers. Faint longitudinal grooves in the palm, situated in a line with the fingers, express slight folds which indicate, where the fingers are approximated to or separated from each other, in adduction and abduction. In some hands a longitudinal groove marks off the muscles of the ball of the little finger from the rest of the palm, and is associated with a slight opponent action of that digit; by the combination of which, with a partial opposition of the thumb, the palm can be hollowed into a cup—the drinking-cup of Diogenes.

These grooves are present in the infant's hands at the time of birth, and I have seen them in an embryo, the spine and head of which were not more than 90 mm. (three and a half inches) long. They appear in the palm months before the infant (three and a half inches) long. They appear in the palm months before the infant can put its hand to any use; though it is possible that the muscles of the thumb and fingers do, even in the embryo, exercise some degree of action, especially in the direction of flexion. These grooves are not therefore acquired after birth. It is a question how far the intra-uterine purposeless movements of the digits are sufficient to produce them; but even should this be the case, it is clear that they are to be regarded as hereditary characters transmitted from one generation of human beings to another. They are correlated with the movements of the digits, which give the functional power and range of movement to the hand of man.

In the palm of the hand of the Anthropoid apes grooves are also seen, which differ in various respects from those in man, and which are characteristic of the group in which they are found. In these animals the palm is traversed by at least two grooves from the index border to that of the minimus. In the Gibbon they are oblique, but in the Gorilla, Chimpanzee, and Orang they are almost transverse, which implies that in flexion the fingers do not move so obliquely towards the comparatively feeble thumb as they do in man. The curved groove which limits the ball of the thumb is present, but on account of the less development of that eminence, it is not so extensive as in man. The longitudinal grooves in the palm are deeper than in the human hand, and in the Gorilla and Orang a groove differentiates the eminence associated with the muscles of the little finger from the adjoining part of the palm. The character and direction of these grooves are such as one would associate with the hand of an arboreal animal, in which the long fingers are the chief digits employed in grasping an object more or less cylindrical, like the branch of a tree, and in which the thumb is a subordinate digit. I have not had the opportunity of examining the palm of the embryo

<figure><img src="image_6.png" /></figure>

<footnote n="1">¹ For a comparative description of the muscles of the hand and foot of the Anthropoid apes consult Dr. Hepburn's memoir in *Journal of Anatomy and Physiology*, vol. xxvi.</footnote>
the fingers. In apes, therefore, as in man, these grooves are not acquired after birth, but have an hereditary signification.

We may now contrast the grooves in the skin of the sole of the human foot with those which we have just described in the palm. For this purpose the foot of an infant must be selected as well as that of an older person in which the toes have not been cramped and distorted by ill-fitting shoes.<fnref n="1" />

The toes are marked off from the sole proper by a deep diagonal depression, which corresponds with the plane of flexion of the first and second phalanges. Behind this depression, and on the sole proper, is a diagonal groove, which commences at the cleft between the great and second toes, and reaches the outer border of the foot. It is seen in the infant, but disappears as the skin of the foot becomes thickened from use and pressure. This groove marks the plane of flexure of the first phalanges on the metatarsal bones of the four smaller toes. Associated with its inner end is a short groove which curves to the inner border of the foot, and marks off the position of the joint between the first phalanx and the metatarsal bone of the great toe. The groove indicates the movements of the great toe in flexion, and in adduction to, or abduction from, the second toe. It has sometimes erroneously been regarded as the corresponding groove in the foot to the deep curved groove in the hand, which defines the muscles of the ball of the thumb and is associated with the movement of opposition. This is not its real character, for the chief joint concerned in opposition is that between the metacarpal bone and the corresponding carpal bone, and not that between the metacarpal bone and the phalanx. In addition, one, or it may be two faint grooves run from within outwards near the middle of the sole. In the infant's foot a groove also extends longitudinally in the centre of the foot. The grooves on the integument of the sole are in harmony with the inner anatomy of the foot, and confirm the statement, already made, that the great toe in man cannot be opposed to the sole, as the thumb can to the palm, for the great curved groove expressing the movement of opposition is wanting.

In the apes, the condition of the integumentary grooves in the sole is very different from the human foot. In the Anthropoid group, the ball of the great toe, with its muscles, is marked off by a deep curved groove, which extends from the margin of the cleft between it and the second toe, backwards along the middle of the sole almost as far as the heel. Its depth and extent are associated with the powerful opponent, or grasping action of the hallux. Two other grooves, in front of that just described, pass obliquely across the sole, from the cleft between the hallux and the second toe, and reach the outer border of the foot. They are associated with the movements of the four smaller toes, and their obliquity shows that, when the foot is used as a prehensile organ, the object is grasped not only by the great toe being moved towards the sole, but by the smaller toes being moved towards the hallux. From these arrangements it is obvious that the pes of the ape is, physiologically speaking, a foot-hand, it is pedimanous. Though anatomically a foot, it can be used not only for support and progression, but for prehension, and, for the latter-named office, the hallux is a more potent digit in the foot than is the pollex in the hand. The external rotation of the thigh at the hip joint, and the power of rotating the leg inwards on the thigh at the knee joint, contribute to make the foot of the ape a more important prehensile instrument, and enable the animal to use it more efficiently for this purpose when sitting, than would have been the case if there had been no contributory movements at the hip and knee.

The power of assuming the erect attitude, the specialisation of the upper limbs

into instruments of prehension, and of the lower limbs into columns of support and progression, are not in themselves sufficient to give that distinction to the human body which we know that it possesses. They must have co-ordinated with them the controlling and directing mechanism placed in the head, known as the brain and organs of sense.

The head, situated at the summit of the spine, holds a commanding position. Owing to the joints for articulation with the atlas vertebra being placed on the under surface of the skull, and not at the back of the head, and to the great reduction in the size of the jaws, as compared with apes and quadrupeds generally, the head is balanced on the top of the spine. The ligaments supporting it and connected with it are comparatively feeble, and do not require for their attachment strong bony ridges on the skull, or massive projecting processes in the spine, such as one finds in apes and many other mammals. The head with the atlas vertebra can be rotated about the axis vertebra by appropriate muscles. The face looks to the front, the axis of vision is horizontal, and the eyes sweep the horizon with comparatively slight muscular effort.

The cranial cavity, with its contained brain, is of absolutely greater volume in man than in any other vertebrate, except in the elephant and in the large whales, in which the huge mass of the body demands the great sensory-motor centres in the brain to be of large size. Relatively also to the mass and weight of the body, the brain in man may be said to be in general heavier than the brains of the lower vertebrates, though it has been stated that some small birds and mammals are exceptions to this rule.

We have abundant evidence of the weight of the brain in Europeans, in whom several thousand brains have been tested. In the men, the average brain-weight is from 49 to 50 oz. (1,390 to 1,418 grm.). In the women, from 44 to 45 oz. (1,248 to 1,283 grm.). The difference in weight is doubtless in part correlated with differences in the mass, weight, and stature of the body in the two sexes, although it seems questionable if the entire difference is capable of this explanation. It is interesting to note that even in new-born children the boys have bigger heads and heavier brains than the girls. Dr. Boyd gives the average for the girl infants as 10 oz., and for boys 11·67 oz. A distinction in the brain weight of the two sexes is obviously established, therefore, before the child is born, and is not to be accounted for by the training and educational advantages enjoyed by the male sex being superior to those of the female sex.

The brains of a number of men of ability and intellectual distinction have been weighed, and ascertained to be from 55 to 60 oz. In a few exceptional cases, as in the brains of Cuvier and Dr. Abercrombie, the weight has been more than 60 oz.; but it should also be stated that brains weighing 60 oz. and upwards have occasionally been obtained from persons who had shown no sign of intellectual eminence.

On the other hand, it has been pointed out by M. Broca and Dr. Thurnam, that if the brain falls below a certain weight it cannot properly discharge its functions. They place this minimum weight for civilised people at 37 oz. for the men, and 32 oz. for the women. These weights are, I think, too high for savage men, more especially in the dwarf races. We may, however, safely assume that if the brain-weight in adults does not reach 30 oz. (851 grm.), it is associated with idiocy or imbecility. There would seem, therefore, to be a minimum brain-weight, which is necessary in order that the mental functions may be actively discharged.

We have unfortunately not much evidence of the weight of the brain in the uncultivated and savage races. The weighings made by Tiedemann, Barkow, Reid, and Peacock give the mean of the brain in the negro as between 44 and 45 oz., a weight which corresponds with that of European women; whilst in the negress the mean weight is less than in the female sex in Europeans. In two Bush girls from South Africa—representatives of a dwarf race—the brain is said to have been 34 and 38 oz. respectively.<fnref n="1" />

From the weighings which have been published of the brains of the Orang and

<footnote n="1">¹ These grooves have been described generally by the late Professor Goodsir (Anatomical Memoirs, vol. i. 1868); by myself in a lecture on hands and feet, Health Lectures, Edinburgh, 1884; and by Mr. Louis Robinson, the last named of whom has called especial attention to their arrangement in the feet of infants (Nineteenth Century, vol. xxxi 1892, p. 795). The integumentary grooves in both hands and feet of men and apes have also been described and figured in detail by Dr. Hepburn in Journal of Anat. and Phys., vol. xxvii. 1893, p. 112.</footnote>

<footnote n="1">¹ Sir R. Quain in Pathological Transactions, 1850, p. 182, and Messrs. Flower and Murie in Journal of Anatomy and Phys., vol. i. p. 206.</footnote>
chimpanzee, it would seem that the brain-weight in these apes ranges from 11 to 15 oz. (312 to 426 grm.), and the brain-weight appears to be much about the same in the Gorilla. These figures are greatly below those of the human brain, even in so degraded a people as the dwarf Bush race of South Africa. They closely approximate to the weight of newly born male infants, in whom, as has just been stated, the average weight was 11.67 oz. For the purposes of ape-life, the low brain-weight is sufficient to enable the animal to perform every function of which it is capable. Its muscular and nervous systems are so accurately co-ordinated that it can move freely from tree to tree, and swing itself to and fro; it can seize and retain objects with great precision, and can search for and procure its food. In all these respects it presents a striking contrast to the infant, having an almost similar brain-weight, which lies helpless on its mother's knee.

Another line of evidence, of which we may avail ourselves, in order to test the relative size of the brain in the different races of men and in the large apes is to be obtained by determining the internal capacity of the cranium. Examples of the brains of different races (except Europeans) are few in number in our collections, but the crania are often well represented, the volume of the cavity in which the brain is lodged can be obtained from them, and an approximate conception of the size and weight of the brain can be estimated. In pursuing this line of inquiry, account has of course to be taken of the space occupied by the membranes investing the brain, by the blood vessels and the cerebro-spinal fluid. A small deduction from the total capacity will have to be made on their behalf.

There is a general consensus of opinion amongst craniologists that the mean internal capacity of the cranium in adult male Europeans is about 1,500 c.c. (91.5 cub. in.). The mean capacity of the cranium of fifty Scotsmen that I have measured by a method, which I described some years ago,<fnref n="1" /> was 1,493 c.c. (91.1 cub. in.). The most capacious of these skulls was 1,770 c.c., and the one with the smallest capacity was 1,240 c.c. Thus, in a highly civilised and admittedly intellectual people, the range in the volume of the brain-space amongst the men was as much as 530 c.c. in the specimens under examination, none of which was known or believed to be the skull of an idiot or imbecile, whilst some were known to be the crania of persons of education and position. In twenty-three Scotswomen the mean capacity was 1,325 c.c., and the range of variation was from a maximum 1,625 to a minimum 1,100 c.c.—viz., 525 c.c.

Again I have taken the capacity, by the same method, of a number of crania of the Australian aborigines, a race incapable apparently of intellectual improvement beyond their present low state of development. In thirty-nine men the mean capacity was only 1,280 c.c. (78.1 cub. in.). The maximum capacity was 1,514 c.c., the minimum was 1,044 c.c. The range of variation was 470 c.c. In twenty-four women the mean capacity was 1,115.6 c.c., the maximum being 1,240 and the minimum 930, and the range of variation was 310 c.c. It is noticeable that in this series of sixty-three Australian skulls, all of which are in the Anatomical Museum of the University of Edinburgh, eight men had a smaller capacity than 1,200 c.c., and only four were above 1,400 c.c. Of the women's skulls ten were below 1,100 c.c., four of which were between 900 and 1,000 c.c., and only three were 1,200 c.c. and upwards.

Time does not admit of further detail on the cranial capacities of other races of men. Sufficient has been said to show the wide range which prevails, from the maximum in the Europeans to the minimum in the Australians, and that amongst persons presumably sane and capable of discharging their duties in their respective spheres of activity; for we must assume that the crania of the Australians, having the small capacities just referred to, were yet sufficiently large for the lodgment of brains competent to perform the functions demanded by the life of a savage. From a large number of measurements of capacity which I have made of the skulls of the principal races of men, I would draw the following conclusions: First, that the average cranial capacity, and consequently the volume and weight of the brain, are markedly higher in the civilised European than in the savage races; second, that the range of variation is greater in the former than in the

latter; third, that in uncivilised man the proportion of male crania having a capacity equal to the European mean, 1,500 c.c., is extremely small; fourth, that though the capacity of the men's skulls is greater than that of the women's, there is not quite the same amount of difference between the sexes in a savage as in a civilised race.

It may now be of interest to say a few words on the capacity of the cranium in the large anthropoid apes. I have measured, by the method already referred to, the capacity of the skulls of five adult male Gorillas, and obtained a mean of 494 c.c., the maximum being 590 c.c. and the minimum 410 c.c., the range of variation being 180 c.c. Dr. Delisle found the old male Orang (Maurice),<fnref n="1" /> which died a short time ago in the Jardin des Plantes, to have a capacity of 385 c.c., whilst the younger male (Max) had a capacity of 470 c.c.<fnref n="2" /> The mean of eleven specimens measured by him was 408 c.c., which is somewhat less than the measurements of males recorded by M. Topinard and Dr. Vogt; but it should be stated that in some of Dr. Delisle's specimens the sex could not be properly discriminated, and possibly some of them may have been females. The cranial capacity of seven male Chimpanzees is stated by M. Topinard to be 421 c.c.

The determination of the mass and weight of the brain as expressed in ounces, and of the capacity of the cranial cavity as expressed in cubic centimetres, are only rough methods of comparing brain with brain, either as between different races of men, or as between men and other mammals. Much finer methods are needed in order to obtain a more exact comparison.

The school of Phrenologists represented in the first half of the century by Gall, Spurzheim, and George Combe, whilst recognising the importance of the size of the brain as a measure of intellectual activity, also attached value to what was called its quality. At that time the inner mechanism of the brain was almost unknown, for the methods had not been discovered by which its minute structure could be determined. It is true that a difference was acknowledged, between the cortical grey matter situated on the surface of the hemispheres and the sub-jacent white matter. Spurzheim had also succeeded in determining the presence of fibres in the white matter of the encephalon, and had, to a slight extent, traced their path. The difference between the smooth surface of the hemispheres of the lower mammals and the convoluted surface of the brain of man and the higher mammals, and the influence which the development of the convolutions exercised in increasing the area of the cortical grey matter, were also known.

A most important step in advance was made, when, through the investigations of Leuret and Gratiolet, it became clear that the convolutions of the cerebrum, in their mode of arrangement, were not uniform in the orders of mammals which possessed convoluted brains, but that different patterns existed in the orders examined. By his further researches Gratiolet determined that in the anthropoid apes, notwithstanding their much smaller brains, the same general plan of arrangement existed as in man, though differences occurred in many of the details, and that the key to unlock the complex arrangements in man was to be obtained by the study of the simpler disposition in the apes. These researches have enabled anatomists to localise the convolutions and the fissures which separate them from each other, and to apply to them precise descriptive terms. These investigations were necessarily preliminary to the histological study of the convolutions, and to experimental inquiry into their functions.

By the employment of the refined histological methods now in use, it has been shown that the grey matter in the cortex of the hemispheres, and in other parts of the brain, is the seat of enormous numbers of nerve-cells, and that those in the cortex, whilst possessing a characteristic pyramidal shape, present many variations in size. Further, that these nerve-cells give origin to nerve axial fibres, through which areas in the cortex become connected directly or indirectly, either with other areas in the same hemisphere, with parts of the brain and spinal cord situated below the cerebrum, with the muscular system, or with the skin and other organs of sense.

<footnote n="1">¹ Human Crania, *Challenger Reports*, Pt. xxix. 1884, p. 9.</footnote>

<footnote n="1">¹ *Nouvelles Archives du Muséum d'Histoire naturelle*, 1895.</footnote>

<footnote n="2">² The stature of Maurice was 1 m 40; that of Max 1 m 28.</footnote>
Every nerve-cell, with the nerve axial fibre arising from and belonging to it, is now called a Neurone, and both brain and spinal cord are built up of tens of thousands of such neurones. It may reasonably be assumed that the larger the brain the more numerous are the neurones which enter into its constitution. The greater the number of the neurones, and the more complete the connections which the several areas have with each other through their axial fibres, the more complex becomes the internal mechanism, and the more perfect the structure of the organ. We may reasonably assume that this perfection of structure finds its highest manifestations in the brain of civilised men.

The specialisation in the relations and connections of the axial fibre processes of the neurones, at their termination in particular localities, obviously points to functional differences in the cortical and other areas, to which these processes extend. It has now been experimentally demonstrated that the cortex of the cerebrum is not, as M. Flourens conceived, of the same physiological value throughout; but that particular functions are localised in definite areas and convolutions. In speaking of localisation of function in the cerebrum, one must not be understood as adopting the theory of Gall, that the mental faculties were definite in their number, that each had its seat in a particular region of the cortex, and that the locus of this region was marked on the surface of the skull and head by a more or less prominent 'bump.'

The foundation of a scientific basis for localisation dates from 1870, when Fritsch and Hitzig announced that definite movements followed the application of electrical stimulation to definite areas of the cortex in dogs. The indication thus given was at once seized upon by David Ferrier, who explored not only the hemispheres of dogs, but those of monkeys and other vertebrates.<fnref n="1" /> By his researches and those of many subsequent inquirers, of whom amongst our own countrymen we may especially name Beevor, Horsley, and Schäfer, it has now been established that, when the convolutions bounding, and in close proximity to the fissure of Rolando are stimulated, motor reactions in the limbs, trunk, head and face follow, which have a definite purposive character, corresponding with the volitional movements of the animal. The Rolandic region is therefore regarded as a part of the motor apparatus; it is called the motor area, and the function of exciting voluntary movements is localised in its cortical grey matter.

By the researches of the same and other inquirers it has been determined that certain other convolutions are related to the different forms of sensibility, and are sensory or perceptive centres, localised for sight, hearing, taste, smell, and touch.

Most important observations on the paths of conduction of sensory impressions in the cortex of the convolutions were announced last year by Dr. Flechsig,<fnref n="2" /> of Leipzig, so well known by his researches on the development of the tracts of nerve-fibres in the columns of the spinal cord, published several years ago. He discovered that the nerve-fibres in the cord did not become myelinated, i.e. attain their perfect structure, at a uniform period of time, so that some acquired their complete functional importance before others. He has now applied the same method of research to the study of the development of the human brain, and has shown that in it also there is a difference in the time of attaining perfect structural development of the nerve-tracts. Further, he has discovered that the nerve-fibres in the cerebrum become myelinated, subsequent to the fibres of the other divisions of the cerebro-spinal nervous axis. When a child is born, very few of the fibres of its cerebrum are myelinated, and we have now an anatomical explanation of the reason why an infant has so inactive a brain and is so helpless a creature. It will therefore be of especial interest to determine, whether in those animals which are active as soon as they are born, and which can at once assume the characteristic attitude of the species, the fibres of the cerebrum are completely developed at the time of birth. Flechsig has also shown that the sensory paths myelinate before the motor tracts; that the paths of transmission of touch, and the other impulses conducted by the dorsal roots of the spinal nerves, are

the first to become completely formed, whilst the fibres for auditory impulses are the last.

Flechsig names the great sensory centre which receives the impulses associated with touch, pain, temperature, muscular sense, &c., Körperfühlsphäre, the region of general-body-sensation, or the somesthetic area as translated by Dr. Barker.<fnref n="1" /> The tracts conducting these impulses myelinate at successive periods after birth. They pass upwards from the inner and outer capsules and the optic thalamus as three systems.<fnref n="2" /> Some enter the central convolutions of the Rolandic area, others reach the paracentral lobule, the inferior frontal convolution, the insula, and small parts of the middle and superior frontal convolutions; whilst considerable numbers reach the gyrus fornicatus and the hippocampal gyrus, which Ferrier had previously localised as a centre of common or tactile sensibility.

The Rolandic area, therefore, is not exclusively a motor area, but is a centre associated also with the general sensibility of the body. The motor fibres in it are not myelinated until after the sensory paths have become developed. As the motor paths become structurally complete, they can be traced downwards as the great pyramidal tract from the pyramidal nerve-cells in this area, from which they arise, into the spinal cord, where they come into close relation with the nerve-cells in the anterior horn of grey matter, from which the nerve axial fibres proceed that are distributed to the voluntary muscles.

Flechsig's observations agree with those of previous observers in placing the visual centre in the occipital lobe; the auditory centre in and near the superior temporal convolution; and the olfactory centre in the uncinate and hippocampal convolutions. Of the position of the taste centre he does not speak definitely, although he thinks it to be in proximity either to the centre of general sensibility, or to the olfactory centre.

The centres of special sense in the cortex, and the large Rolandic area, which is the centre both for motion and general sensation, do not collectively occupy so much as one-half of the superficial area of the convolutions of the cortex. In all the lobes of the brain—frontal, parietal, occipito-temporal, and insula—convolutions are situated, not directly associated with the reception of sensory impressions, or as centres of motor activity, the function of which is to be otherwise accounted for. These convolutions lie intermediary to the sensory and motor centres. Flechsig has shown that in them myelination of the nerve-fibres does not take place until some weeks after birth, so that they are distinctly later in acquiring their structural perfection and functional activity. As the nerve-fibres become differentiated, they are seen to pass from the sense-centres into these intermediate convolutions, so as to connect adjacent centres together, and bring them into association with each other.<fnref n="3" /> Hence he has called them the Association centres, the function of which is to connect together centres and convolutions otherwise disconnected.<fnref n="4" />

We have now, therefore, direct anatomical evidence, based upon differences in their stages of development, that, in addition to the sensory and motor areas in the

<footnote n="1">¹ West Riding Asylum Reports, 1873.</footnote>

<footnote n="2">² Die localisation der Geistigen Vorgänge, Leipzig, 1896.</footnote>

<footnote n="1">¹ Johns Hopkins Bulletin, No. 70, January 1897.</footnote>

<footnote n="2">² Drs. Ferrier and Aldren Turner communicated to the Royal Society of London a few weeks ago (Proc. R.S. June 17, 1897) an account of an elaborate research on the tracts which convey general and special sensibility to the cerebral cortex of monkeys. Their results were obtained by the aid of destructive lesions and the study of the consecutive degenerations in the nerve-tracts. From the brief abstract in the Proceedings, their research, though conducted by a different method, harmonises with the observations of Flechsig on the human brain, in regard to the course and connections of the great thalamic cortico-petal sensory fibres. They have also traced association fibres in connection with both the visual and auditory systems.</footnote>

<footnote n="3">³ The term association fibres was introduced a number of years ago to express fibres of the cerebrum which connect together parts of the cortex in the same hemisphere. Flechsig's fibres belong to this system.</footnote>

<footnote n="4">⁴ The Association centres had previously been referred to by other observers as 'silent portions' of the cortex, not responding to electrical stimulus. Their possible function had been discussed by Professor Calderwood in *Relations of Mind and Brain*, 2nd edit., 1884.</footnote>
cortex of the human brain, a third division—the association centres—is to be distinguished.

In we compare the cerebrum in man and the apes, we find those convolutions which constitute the motor and sensory centres distinctly marked in both. An ape, like a man, can see, hear, taste, smell and touch; it also exhibits great muscular activity and variety of movement. It possesses, therefore, similar fundamental centres of sensation and motion, which are situated in areas of the cortex, resembling in arrangement and relative position, though much smaller in size than, the corresponding convolutions in the adult human brain. It is not unlikely, though the subject needs additional research, that the minute structure of these centres resembles that of man, though, from the comparatively restricted area of grey matter in the ape, the neurones will necessarily be much fewer in number.

In the cerebrum of a new-born infant, whilst the motor and sensory convolutions are distinct, the convolutions for the association areas, though present, are comparatively simple, and do not possess as many windings as are to be seen in the brain of a chimpanzee not more than three or four years old.

Again, if we compare the brain of the Bushwoman, miscalled the Hottentot Venus, figured by Gratiolet and by Bischoff, or the one studied by Mr. John Marshall, with that of the philosopher Gauss, figured by Rudolph Wagner, we also recognise the convolutions in which the motor and sensory areas are situated. In all these brains they have a comparative simplicity of form and arrangement which enables one readily to discriminate them. When we turn, however, to the association areas in the three tiers of convolutions in the frontal lobe, and in the parieto-occipital and occipito-temporal regions where the bridging or annectant convolutions are placed, we cannot fail to observe that in a highly-developed brain, like that of Gauss, the association convolutions have a complexity in arrangement, and an extent of cortical surface much more marked than in the Bushwoman, and to a still greater degree than in the ape. The naked-eye anatomy of the brain therefore obviously points to the conclusion that these association areas are of great physiological importance.

The problem which has now to be solved is the determination of their function. Prolonged investigation into the development and comparative histology of the brain will be necessary before we can reach a sound anatomical basis on which to found satisfactory conclusions. It will especially be necessary to study the successive periods of development of the nerve-fibre tracts in the cerebrum of apes and other mammals, as well as the magnitude and intimate structure of the association areas in relation to that of the motor and sensory areas in the same species.

Flechsig, however, has not hesitated to ascribe to the association centres functions of the highest order. He believes them to be parts of the cerebral cortex engaged in the manifestations of the higher intelligence, such as memory, judgment, and reflection; but in the present state of our knowledge such conclusions are of course quite speculative.

It is not unlikely, however, that the impulses which are conveyed by the intermediate nerve-tracts, either on the one hand, from the sense centres to the association centres, or on the other, from the association centres to the sensory and motor centres, are neither motor nor sensory impulses, but a form of nerve energy, determined by the terminal connections and contacts of the nerve fibres. It is possible that the association centres, with the intermediate connecting tracts, may serve to harmonise and control the centres for the reception of sensory impressions that we translate into consciousness, with those which excite motor activity, so as to give to the brain a completeness and perfection of structural mechanism, which without them it could not have possessed.

We know that an animal is guided by its instincts, through which it provides for its individual wants, and fulfils its place in nature. In man, on the other hand, the instinctive acts are under the influence of the reason and intelligence, and it is possible that the association centres, with the intermediate association fibres which connect them with the sensory and motor centres, may be the mechanism through which man is enabled to control his animal instincts, so far as they are dependent on motion and sensation.

The higher we ascend in the scale of humanity, the more perfect does this control become, and the more do the instincts, emotions, passions and appetites become subordinated to the self-conscious principle which regulates our judgments and beliefs. It will therefore now be a matter for scientific inquiry to determine, as far as the anatomical conditions will permit, the proportion which the association centres bear to the other centres both in mammals and in man, the period of development of the association fibres, in comparison with that of the motor and sensory fibres in different animals, and, if possible, to obtain a comparison in these respects between the brains of savages and those of men of a high order of intelligence.

The capability of erecting the trunk; the power of extending and fixing the hip and knee joints when standing; the stability of the foot; the range and variety of movement of the joints of the upper limb; the balancing of the head on the summit of the spine; the mass and weight of the brain, and the perfection of its internal mechanism, are distinctively human characters. They are the factors concerned in adapting the body of man, under the guidance of reason, intelligence, the sense of responsibility and power of self-control, for the discharge of varied and important duties in relation to himself, his Maker, his fellows, the animal world and the earth on which he lives.

<figure><img src="image_7.png" /></figure>

PRINTED BY
SPOTTISWODE AND CO., NEW-STREET SQUARE
LONDON
<figure><img src="image_8.png" /></figure>

INSTITUT
DE

PALEONTOLOGIE
HUMAINE
PARIS