# The Works of William Harvey/Anatomical Exercises on the Generation of Animals/Of the Uterine Membranes and Humours

ON
THE UTERINE MEMBRANES AND HUMOURS.
OF THE
UTERINE MEMBRANES AND HUMOURS.
"Four kinds of bodies" are enumerated by Hieronymus Fabricius "as existing externally to the fœtus; these are the umbilical vessels, the membranes, the humours, and a fleshy substance." On these subjects, guided by my observations, I shall briefly state wherein I differ from him; first, however, giving his statement in his own words.
"There are," he says, "three membranes, two of which envelope the whole fœtus, but the third does not do so. Of those which envelope the whole fœtus, the innermost, immediately investing one, is called ἄμνιον, i.e. the mantle. That which follows next is entitled by the Greeks χόριον; the Latins, however, have not given it a name, although some interpreters have thought proper erroneously to call it "secundæ" or "secundina," the secundines; this also envelopes the entire fœtus. The third is called ἀλλαντοειδὴς, i.e. gut-like, from its resemblance to a stuffed intestine; it does not entirely encompass the fœtus, but is applied upon the thorax and part of the abdomen, and extends to either horn of the uterus." He allows that this last membrane is only found in the fœtus of the sheep and cow; he asserts also that it is continuous with the urachus, and by means of this receives the urine from the bladder. Hence, he goes on, "horned animals, in whom this allantois is found, have the urachus so wide and straight, that it resembles a small intestine; it gradually decreases in size until it reaches the fundus of the bladder; whence it would appear to owe its ​origin rather to the intestine than to the bladder itself. But in man and other animals furnished with incisors in both jaws, and in whom the allantois is wanting, the size of the urachus is so diminished, that although it rises from the fundus of the bladder as a single tube, it afterwards splits into innumerable fibres, which pass beyond the umbilicus together with the vessels, and carry the urine into the chorion, although the exact mode in which it does so cannot be demonstrated." On this ground he accuses Arantius of a double error—first, his denial of the existence of the urachus in man; and, secondly, his assertion that the fœtus passes its urine through the genital organs.
For my own part, I must confess I am a willing party to the errors of Arantius, if errors they are to be called. For I am quite sure, if pressure be made on the bladder of a full-grown fœtus, whether of man or of any other animal, that urine will flow by the genitals. But I have never seen an urachus, nor observed that the urine is propelled into the membranes by making pressure on the bladder. I have indeed seen in the sheep and deer what appeared to be a process of bladder between the umbilical arteries, and which contained urine; but it in no way resembled the urachus as described by Fabricius. Not that I would obstinately deny the existence of an allantois; for the minor membranes are so delicate and transparent (those, for example, which we have described as existing between the two "whites" of the egg) that they may easily escape observation. Moreover, in the hen's egg a white excrementitious matter, and even fæces are found between the colliquament and albumen, i.e. between the amnion and chorion; this I have mentioned before, and Coiterus has also observed it. Added to which, the membrane of the colliquament itself, in which the fœtus swims, although it is so exceedingly transparent and delicate that Fabricius himself allows nothing can be imagined more so, nevertheless (for according to him all membranes, however thin, are double) may nature sometimes find herself compelled to deposit urine or some other matter between its duplicatures. An allantois of this kind I am ready to allow Fabricius; but that other intestine-like body produced into either horn of the uterus, I do not discover among the membranes in cloven-footed animals, nor aught else, in ​fact, except the conception itself. I can only find, as I before said, a process of the bladder, situated between the umbilical arteries, which contains an excrementitious matter, and varies in length in different animals. Wherefore, in my opinion, the tunic which Fabricius calls the allantois is, in fact, the chorion; and the ancients applied the name of allantois to it on account of its resemblance to a double intestine. For that external membrane, constricted in the middle, and resembling a saddle-bag in form, which is stretched upwards to each horn of the uterus, and in its passage is pinched in by that part of the uterus which connects the horns, is in truth the chorion; and in the sheep, goat, roe, fallow-deer, and other cloven-footed animals, it can be raised by the hand in the middle of its course, and easily extracted whole; this is the same as what is called the "conception" or ovum. Like an egg, it contains within itself two fluids, and the fœtus with its appendages; it is possessed besides of those characters which Aristotle attributes to the egg; these are, that out of part of it the embryo is originally formed, and that the remainder constitutes the sustenance of the new animal, as has been frequently explained. I believe, then, the tunic which Fabricius called the allantois to be either the chorion or else some unnatural structure formed out of the reduplication of the membranes. It is accordingly only found to exist in some animals, and not always in these; it cannot be traced from the commencement of conception, and in some animals it is more apparent than in others: whilst in others nothing can be seen except a mere process of the bladder. Besides, Fabricius himself allows that its purpose is not to envelope the fœtus, but to contain its urine. In truth, I must think that he has described it rather to defend the doctrine of the ancients, than because he really believed he had discovered such a membrane, or that it served any good purpose. For he allows, with the ancients, and every medical school, that the chorion contains urine, when he says that there are two humours encircling the fœtus, one, viz. in the amnion, consisting of sweat; the other in the chorion, consisting of urine. It is, therefore, clear that the ancients under the two names understood one and the same membrane; and that in ​the cloven-footed animals they called it "allantois," on account of its form; but in others "chorion," because they thought its object was to receive the urine. Wherefore they allow that this tunic is neither found in man nor any of the other animals. For what need can there be of another tunic to retain the urine, when they themselves admit that the office of doing so belongs especially to the chorion? There can be no probable reason assigned why this tunic should exist in the sheep, goat, and the other cloven-footed animals, and not also in the dog, cat, mouse, and others. For in truth, if the object of this membrane were to contain the urine, the fœtus of the sheep and cow must secrete a much larger quantity than those of animals furnished with incisors in both jaws; there must then either be three different humours, or at least two receptacles for the urine. For myself, I am sure that the chorion from the first is full of water. I will not, however, enter into controversies; I would rather record what I have found by my own observations.
To do as Fabricius has done, and give the structure of the full-grown and perfect embryo, is one thing, but it is another to enter fully on the subject of its generation and first formation: just as they are very different things to describe the ripe fruit of an apple or any other tree, and to explain the manner in which it is produced from the germ. I will, therefore, briefly go through the stages by which the "conception" is brought to maturity, in which way the true doctrines in the matter of the membranes and other fœtal appendages will be better ascertained.
In the production of all living creatures, as I have before said, this invariably holds, that they derive their origin from a certain primary something or primordium which contains within itself both the "matter" and the "efficient cause;" and so is, in fact, the matter out of which, and that by which, whatsoever is produced is made. Such a primary something in animals (whether they spring from parents, or arise spontaneously, or from putrefaction) is a moisture inclosed in some membrane or shell; a similar body, in fact, having life within itself either actually or potentially; and this, if it is generated within an animal and remain there, until it produce an "univocal" (not equivocal) animal, is commonly called a "conception;" but if it is exposed to the air by birth, or assumes its beginning under other ​circumstances, (than within an animal), it is then denominated an "egg," or "worm." I think, however, that in either case the word "primordium" should be used to express that from whence the animal is formed; just as plants owe their origin to seeds: all these "primordia" have one common property—that of vitality.
I find a "primordium" of this kind in the uterus of all viviparous animals before any trace of a fœtus appears: there is a clear, thick, white fluid (like the albumen of the egg) inclosed in a membrane, and this I call the ovum. In the roe, fallow-deer, sheep, and other cloven-footed animals, it fills the whole uterus and both its horns.
In process of time an extremely limpid and pure watery fluid (similar to that which in the hen's egg I have called the colliquament) is secreted by this "primordium" or "ovum;" in clearness and brilliancy far exceeding the remaining fluid of the ovum in which it is contained. It is of a circular form, and inclosed in a very delicate and transparent membrane of its own called the "amnion." The other fluid, of a denser and thicker character, is contained in the outer envelope, or chorion, which is in immediate contact with the concave surface of the uterus, and which also encompasses the entire ovum: the shape of this second membrane varies according to that of the uterus: in some animals it is oval, in others oblong, but in those with cloven feet it resembles a saddle-bag. After a short time a red pulsating point shows itself within the transparent substance, and from this point exceedingly fine twigs, or rather rays of vessels, start forth. By and by the first aggregated portion of the body makes its appearance, folded upon itself orbicularly, and somewhat resembling a grub: the remaining parts follow in the order described in our history. For I have ascertained that the production of the fœtus from their ova or "conceptions" in viviparous animals, takes place exactly in the same way as the growth of the chick within the egg.
As I before observed, "conceptions" in viviparous animals vary in form, number, and in their modes of attachment to the uterus. At first, especially in the cloven-footed animals, the "conception" does not adhere to the uterus, but is only in contact with, and fills and distends the organ, and can be easily ​extracted entire. In cloven-footed animals, which conceive within the horns of the uterus, and also in the solidungula, one ovum only of this kind is found, and that stretching up into either horn of the uterus: and although these animals sometimes produce one, sometimes two young at a birth, and so sometimes one, sometimes two colliquaments are found, one in the right, the other in the left horn of the uterus, yet the two are always contained in one and the same ovum.
In other animals, however, the number of ova answers to the number of fœtuses, and within them are as many colliquaments: this is the case in the dog, cat, mouse, and other animals of this kind with teeth in either jaw. In cloven-footed animals the ovum is shaped like a saddle-bag: the form, in fact, under which Fabricius represented the allantois. In the mare, the figure of the uterus internally resembles an oblong bag; in the woman it is of a globular form.
In animals in whom the "conception" adheres to the uterus, (and in very many it does not do so until the foetus is fully formed), this takes place in various modes. In some it is adherent in one place by the intervention of a fleshy substance, which in the woman is called the "placenta," from its resemblance to a round cake (placenta): in others it is attached at many points by certain fleshy bodies, or "carunculæ:" these are five in number in the hind and doe; more numerous, but of smaller size, in the cow; and in the sheep they are in great numbers and of various sizes. In dogs and cats these fleshy bodies entirely surround each ovum like a girdle. A similar substance, in the hare and mole, grows to the side of the uterus: like the human placenta, which embraces about half the "conception," (just as the cup does the acorn at the commencement of its growth), it is attached by its convex aspect to the uterus, and by its concave surface to the chorion.
With these observations premised, I shall now state my opinions on the humours, membranes, fleshy substance of the uterus, and the distribution of the umbilical vessels, in the order described by Fabricius.
The words δεύτερα and ὕστερα are correctly understood by Fabricius to answer to "secundæ" and "secundina" (the ​secundines) and by these are implied not only the membranes, but everything which comes away from the uterus at the last stage of parturition, or at least not long after it, viz. the humours, membranes, fleshy substance, and umbilical vessels.
Of the Humours.
The doctrines inculcated on the subject of the humours, and which, as being entertained by the ancients, Fabricius regards as certain truths requiring no further proof, are altogether inconsistent and false; the doctrines, I mean, that the fluid within the amnion, wherein the fœtus swims, consists of sweat; and that within the chorion of urine. For both these humours are found in the "conception" before any trace of the fœtus is visible; added to which, the fluid they call urine can be seen before that which they regard as sweat. In truth, these humours, especially the outer one, may be observed in unfruitful conceptions where nothing like a fœtus is discoverable.
Women sometimes expel conceptions of this kind, analogous to the subventaneous or wind egg. Aristotle says they are called "fluxes;" among ourselves they are termed "false conceptions," or "slips." An ovum of this kind was aborted in the case of Hippocrates's pipe-player. "In all creatures," we are informed on the authority of Aristotle, "which breed another within themselves, immediately on conception an egg-like body is formed; that is to say, a body in which a fluid is contained within a delicate membrane just like an egg with the shell removed." The humour in the chorion, which Fabricius and other physicians consider to be urine, Aristotle seems to have regarded as the seminal fluid (spermatis sive genituræ liquor). He says, "when the semen is received into the uterus, after a certain time it becomes surrounded by a membrane, and if expulsion takes place before the fœtus is formed, it has the appearance of an egg with the shell removed and covered by its membrane: this mem​brane, moreover, is loaded with vessels." It is, in fact, the chorion; so called from the conflux or multitude of veins. I have often observed ova of this kind escape in the second and third month; they are frequently decomposed internally, and come away gradually in the form of a leucorrhoeal discharge, and thus the hopes of the parent are lost.
Another reason why these humours cannot be sweat and urine, is, that they exist in such abundance at the very beginning;—for the purpose, no doubt, of preventing the body of the fœtus from coming in contact with the adjacent parts when the mother runs, jumps, or uses violent exertion of any kind.
Added to which, many animals never sweat at all, (and we must remember what is said by Aristotle, "that all creatures which swim, walk, or fly," I will add serpents and insects, whether viviparous or oviparous, or generated spontaneously, "are produced after the same manner,") as is the case with birds, serpents, and fishes, which neither sweat nor pass urine. The dog and cat also never sweat; neither in fact does any animal in which the urinary secretion is very abundant. Besides, it is impossible that urine can be passed before the kidneys and bladder are formed.
Moreover, and this is the strongest argument that can be brought forward, those humours can never be excrementitious into which so many branches of the umbilical vessels are distributed by means of the chorion; these vessels, in fact, in this manner taking up nourishment, (as it were from a large reservoir,) and then conducting it to the fœtus.
Besides what need is there of an allantois, if the fluid within the chorion is urine? And if that in the amnion is sweat, why does Nature, who contrives all things well, ordain that the fœtus should float about in its own excrement? And why, too, should the mother (as is the case with some animals) immediately after birth, so greedily devour the excretions of its own offspring, together with the containing membranes? Some have even observed that if the animal fails to eat up these matters it does not give its milk freely.
Notwithstanding these arguments, it may possibly be ima​gined by some that the humours which I believe serve for the nutrition of the fœtus are excrementitious, led chiefly by the fact that they increase as the fœtus grows larger, and in some animals are observed to exist in immense quantities at the period of birth (at which time it might be supposed that all alimentary matters would have been absorbed), and serve besides other uses hardly compatible with their supposed function of nutrition. I nevertheless most confidently assert my belief that these humours are at the commencement destined for the nourishment of the fœtus, just as the colliquament and albumen are in the case of the chick; but that, in course of time, when the thinner and purer portions are absorbed, the remainder takes on the character of excrementitious matter, but still has its uses, and in some animals especially conduces to the safety of the fœtus, and also greatly facilitates birth. For just as wine becomes poor and tasteless when the spirit has evaporated; and as all excreted matters owe their origin for the most part to what has been previously food; so, after all the nutrient portions of the fluid contained in the chorion have been taken up by the fœtus, the remainder become excrementitious, and is applied to the above-mentioned uses. But all the fluid of the amnion is usually consumed by the time of birth; so that it is probable the fœtus seeks its exit on account of deficiency of nutriment.
Lastly, if any other fluid is ever contained within the allantois, and this is sometimes the case, I believe it to be unnatural. For sometimes we see women at their delivery have an enormous flow of water, sometimes a distinctly double flow; and this the midwives call the "by-waters." And so some women are seen with the abdomen immensely distended, and yet they bring forth a little shrivelled fœtus accompanied by a vast flow of water. Some imagine that a larger quantity of water is found with weakly and female children, whilst stronger and male fœtuses have a smaller share. I have often seen the waters come away in the middle of pregnancy, and abortion not take place, the child remaining strong and vigorous until birth. Since, then, there are naturally two collections of fluid, one in the chorion, the other in the amnion, so it sometimes happens that unnatural accumulations take place either in membranes of their own, or between the duplicatures of the chorion.
Of the Membranes.
With respect to the membranes or tunics of the uterus; as their special office is to contain the "waters," and as these waters are two only, it is pretty certain that the membranes themselves do not necessarily or usually exceed that number.
Those who enumerate three tunics are, I believe, in error, owing to the ancients having described the same membrane at one time under the title of "chorion," from the concourse of veins, at another under the name of "allantois" from its form.
Unquestionably, every "conception" is inclosed in two envelopes, just as the brain is surrounded by its two membranes; every tree and fruit, moreover, has it double bark; and lastly, seeds and fruits are protected by a double covering, the outermost of which is harder and stronger than the inner one.
Of the above-mentioned membranes, the innermost (that which contains the colliquament or purer fluid,) is exceedingly delicate; it is called the "amnion," i. e. the mantle, from the way in which it is disposed round the fœtus. The outer tunic, however, is much thicker and stronger, and has received the name of "chorion," "because," says Fabricius, "a multitude of arteries and veins are aggregated together and arranged in it, as it were, after the manner of a chorus. Hence one of the tunics of the eye has been denominated χοροειδὴς (choroid) from its vessels having a similar arrangement to those in the chorion; the plexus of arteries and veins in the ventricles of the brain has also gained its name from the same circumstance."
The chorion fills the whole uterus, and contains a viscid and rather turbid fluid; whilst the placenta, or carunculæ, adhere to its outer surface, and thus attach the "conception" to the uterus.
In the woman it is usually adherent to the amnion at its lower portion; nor can it be separated there without difficulty.
In cloven-footed animals the chorion is of very large size, and contains a hundred times more fluid than the amnion: this last membrane at first is scarcely as large as a nutmeg, or broad bean, and is generally found in one or other horn of the uterus; that, namely, in which the embryo lies.
​In the woman, more particularly, the chorion is externally rough and viscous, but internally it is smooth, slippery, and interwoven with abundance of vessels. In the woman, also, the upper part is thick and soft, but the lower is thinner and more membranous in character.
The placenta in the woman grows to the upper part of this membrane. In the sheep, numerous carunculæ adhere to it at various points. In the fallow and red deer the ovum is united to the uterus in five places only; whilst in the mare it is in contact with the inner surface of the uterus by an almost infinite number of points of attachment. Hence Fabricius states that in almost all viviparous animals there is a soft, loose, porous, and thick fleshy body of a dark colour, in intimate union with the terminations of the umbilical vessels; he compares it to a sponge, or to the loose parenchyma of the liver or spleen; hence, too, it was called by Galen "glandular flesh;" and it is now commonly known by the name of the uterine liver, in which the extremities of the umbilical vessels ramify to bring nutriment from the uterus to the fœtus.
But this fleshy substance is not found in all animals, nor at all periods of utero-gestation; but in those alone in which the conception adheres to the uterus; and then only when it becomes attached for the purpose of taking up nutriment. At the commencement the "conception" (like an egg placed within the uterus) is found in contact with every part of the uterus, yet at no point is it adherent; but produces and nourishes the embryo out of the humours contained within it, as I have explained in the instance of the hen's egg. This adhesion, or growing together, first takes place, and the fleshy mass (constituting the bond of union between the "conception" and the uterus) is first produced, when the fœtus becomes perfectly formed, and, through want either of different or more abundant nourishment, dispatches the extremities of the umbilical vessels to the uterus, that from hence, (as plants do from the earth by their radicles) it may absorb the nutrient juices. For in the beginning, as I have said, when the "punctum saliens" and the blood can alone be seen, the ramifications of the umbilical vessels are only visible in the colliquament and amnion. When, ​however, the fabric of the body is completely formed, the ramifications extend further, and are distributed in vast numbers throughout the chorion, that from the albuminous fluid which there exists, they may obtain nourishment for the fœtus.
Hence it is manifest that the young of viviparous animals are at the beginning nourished in exactly the same manner as the chick in the egg; and that they are detained within the uterus in order that (when they can no longer supply themselves with nutriment from their own stores) they may form adhesions to it by means of this fleshy substance, and receiving more abundant supplies of food from the mother, may be nourished and made to grow.
Wherefore Fabricius has rightly observed, that in some animals the "conception" is scarcely attached to the uterus at all. Thus the sow and the mare have no such fleshy mode of union,—but in them the ovum or @conception," as in the beginning it is formed out of the humours of the uterus, so it is nourished subsequently by the same means; just as the ovum of the hen is supplied with aliment at the expense of the albuminous matter without any connexion whatever with the uterus: and thus the fœtus is furnished with aliment by the conception" in which it is contained, and is nourished as the chick is from the fluids of the egg. This is a strong argument that the fœtus of viviparous animals is no more nourished by the blood of the mother than the chick in the egg; and moreover, that the fluid within the chorion is neither urine nor any other excrementitious matter; but serves for the support of the fœtus. Although, as I have before remarked, it is possible when all the nutrient portions have been taken up, the remainder may degenerate into excrementitious matter resembling urine. This is also clear from what I formerly observed of the cotyledons in the deer, viz., that in these animals the fleshy mass was of a spongy character, and constituted, like a honeycomb, of innumerable shallow pits filled with a muco-albuminous fluid, (a circumstance already observed by Galen); and that from this source the ramifications of the umbilical vessels absorbed the nutriment and carried it to the fœtus: just as, in animals after their birth, the extremities of the mesenteric vessels are spread over the coats of the intestines and thence take up chyle.
Of the Placenta.
In my opinion, then, the placenta and carunculæ have an office analogous to that of the liver and mamma. The liver elaborates for the nourishment of the body, the chyle previously taken up from the intestines: the placenta, in like manner, prepares for the fœtus alimentary matters which have come from the mother. The mammæ also, which are of a glandular structure, swell with milk, and although in some animals they are not even visible at other times, they become full and tumid at the period of pregnancy; so, too, the placenta, a loose and funguslike body, abounds in an albuminous fluid, and is only to be found at the period of pregnancy. The liver, I say, then, is the nutrient organ of the body in which it is found; the mamma is the same of the infant, and the placenta of the embryo. And just as the mother forms more milk from her food than is requisite to sustain her own flesh and blood, which milk is digested and elaborated in the mamma; so do those animals, furnished with a placenta, supply to the fœtus nourishment which is purified in that organ. Hence it happens that the embryo is furnished with good or bad nutriment just as the mother takes wholesome or unwholesome food, and in proportion as it is elaborately prepared or not in these uterine structures. For some embryos have a more perfect structure provided for them, such as that fleshy substance mentioned above, which in some is altogether wanting. In some, also, the placenta is observed to be thicker, larger, and more loaded with blood; whilst in others it is more spongy and white, like the thymus or pancreas. But there is not more variety found in the placenta than in the mamma or viscera generally: for instance, the liver in some animals is red and filled with blood, in others, as is the case with fishes and some cachectic persons in the human species, it is of much paler hue. The mare feeds on crude grass, and does not ruminate; the sow gorges itself with any unclean food; and in both the placenta, or organ for perfecting the aliment, is wanting.
Rightly then is it observed by Fabricius, that "this fleshy ​structure, differs much in shape, size, position, and number in different kinds of animals. The human female has one placenta only; as is the case with the mouse, rabbit, guinea-pig, dog, and cat:" so also with many animals which have the toes distinct, and incisor teeth in both jaws. "All those which have the hoof cloven and incisors in one jaw only, have several placentæ, whether they be domesticated animals, like the sheep, cow, and goat, or wild, as the red-deer, roe, fallow-deer, and others of the same kind. Again, where there is only one of these fleshy structures it either resembles a cake, (whence its name placenta), as in the human female, rabbit, hare, mole, mouse, and guinea-pig; or else it is like a girdle or bandage encircling the trunk of the body, as in the dog, cat, ferret, and the like." In some it resembles the cup or chalice of the acorn, and surrounds the greater part of the "conception," as in the hare and rabbit, its convex part adhering to the uterus, the concave looking towards the fœtus. "Again, in animals which have this structure in the form of a cake, although the shape is similar, the situation in which it is found is very different. In the human female it adheres to the fundus of the uterus, and is as far removed from the fœtus as possible, their connexion being effected by means of long vessels. In the mouse, guinea-pig, and rabbit, it is attached partly in the region of the loins, partly at the sides of the thorax. Those animals which have numerous placentæ are all furnished with incisors in one jaw only, as the sheep, cow, goat, red-deer, roe, and the like. Yet in these some variety is observable."
For in the sheep the carunculæ are many in number, and of different magnitudes, the largest being of the size of a nutmeg, the smallest of that of a pea or vetch: they are also of a rounded form and reddish hue, with their convex portion turned towards the uterus, something in the semblance of soft warts or nipples. "In the cow they are larger, wider, and whiter, more like a spongy or fungoid body," and they appear to take their origin from the chorion. In the red or fallow-deer they are five only in number; these spring from the walls of the uterus, and thrust themselves inwards, exhibiting their depressions or acetabula on the side of the fœtus. But in all animals it is observed that the carunculæ adhere firmly to the uterus, and cannot be separated from it without considerable difficulty, ​except at the period of birth; at which time they become loosened from their attachments and fall like ripe fruit. If they are forcibly torn from the uterus, I have observed the greater part of the blood that escapes to flow, not from the "conception," but from the uterus itself.
Fabricius, when discussing the mode of union between the "fleshy substance" and the uterus, uses many arguments, but in my opinion weak ones, to prove that the umbilical vessels anastomose with those of the uterus: yet he seems chiefly to have done so to countenance the old opinion once held almost by all; for he confesses that he can make no positive assertion on the subject, "because the fleshy mass itself stands in the way of any accurate investigation." Yet neither reason nor observation would lead us to believe that more anastomoses exist in the uterus, than in the liver between the branches of the vena portæ and the cava; or in the mamma, between the vessels which transmit blood and those which carry milk. There may be, indeed, at places a juxtaposition of vessels, and sometimes the insertion of one into the coats of another; but the perfect coalition and union, described by Fabricius, never exist. Were it so, the veins and arteries ought to be continuous; for the vessels which bring the blood from the mother into the uterus and carunculæ are arteries, whilst those which pass from the uterus to the fœtus are veins, as is readily apparent; for they carry blood from the placenta into the vena cava.
Hence the opinion of Arantius seems to me to be the true one, viz. that the orifices of the umbilical veins are in no way continuous with the uterine vessels. For there is a smaller number of vessels carrying blood to the uterus than there is of veins returning it to the fœtus; and the greater part of the roots of those terminate in the chorion. Yet Fabricius, either from respect to the ancients, or through an envious feeling towards Arantius, most pertinaciously holds to the old opinion.
Of the Acetabula.
Fabricius has ascertained nothing on the subject of the "cotyledons" or "acetabula;" he gives only the various opinions of the ancients. In the former part of my work, however, in the history of the fœtus in the deer, I have mentioned the animals in which acetabula are found; at the same time I described them as constituting numerous cells of a small size scattered throughout the carunculæ, or "fleshy substance," and filled with an albuminous or mucilaginous fluid, like a honeycomb full of honey.
In the deer they greatly resemble in shape the cavity of the haunch-bone which receives the head of the thigh; hence their name in Greek, κοτυλήδονες (little measures); and in Latin, acetabula, because they resemble the little cups formerly brought to table filled with vinegar for sauce.
These cavities do not exceed in size the holes in a large sponge, and a delicate ramification of the umbilical vessels penetrates deeply into each of them; for in them aliment is laid up for the fœtus, not indeed constituted of blood, as Fabricius would have it, but matter of a mucous character, and greatly resembling the thicker part of the albumen in the egg. Hence it is clear, as I have before observed, that the fœtus in cloven-footed animals (as indeed in all others) is not nourished by the blood of the mother.
Aristotle's statement, "that the acetabula gradually diminish with the growth of the fœtus, and at last disappear," is not borne out by experiment; for as the fœtus increases so do the carunculæ; the acetabula at the same time become more capacious and numerous, and more full of the albuminous matter.
If the carunculæ are pressed no blood escapes, but just as water or honey can be squeezed from a sponge or honeycomb, so if pressure is made a whitish fluid oozes from out of the acetabula, which then become shrunk, white, and flaccid, and at last come to resemble a nipple, or a large flabby wart.
​Aristotle asserts, with truth, that acetabula are not found in all animals; for they do not exist in the woman, nor (as far as I know) in any animal which possesses a single fleshy substance or placenta. As to the uses of the carunculæ, I believe that, like the mamma, they elaborate not blood but a fluid resembling albumen, and that this serves for the nourishment of the fœtus.
Of the Umbilical Cord.
Fabricius gives an elegant description, as well as most beautiful figures, of the umbilical vessels. "The veins," he says, "which pass from the uterus in the direction of the fœtus are always closely united and become larger and larger as they proceed; nor does this mutual interlacement cease until all end in two large trunks; these penetrate the fœtus at the umbilicus, and become one vein of great size, which is inserted into the liver of the fœtus, and has a communication both with the vena cava and vena porta. In like manner the arteries which accompany the veins, being many in number and exceedingly minute, pass from the uterus towards the fœtus, and, gradually uniting and increasing in size, terminate in two large trunks; these, after penetrating the umbilicus, separate from the veins, and attaching themselves to the lateral surface of the bladder by the intervention of a membrane, proceed downwards on either side and become continuous with the branches of the aorta descending to the thigh." It must be observed, however, that this description of Fabricius applies only to the umbilical vessels of the human fœtus, and not to the young of every animal. Nor even does it hold in the case of the human fœtus except when it is full grown; for at the beginning the arteries make little show, and are so small as to require the eyes of a lynx to see them; nor afterwards indeed are they distinguishable except by their pulsation: in other particulars they resemble veins. Since then, as I have elsewhere shown, the very small branches of arteries do not pulsate, in so far as the eye is concerned, there can be no difference between them and veins. The arteries, I say, at this time are so fine and ​minute, that they are woven, as it were, like the most delicate threads, into the tissues of the veins, or rather in some obscure manner insinuate themselves into them; hence they almost entirely elude the sight. But all the veins, by a retrograde movement, unite their twigs and terminate in one trunk like the branches of a tree, in the same manner as the mesenteric veins, all of which terminate in the vena portæ.
Near the embryo [the umbilical veins] are divided into two trunks, but when entered within it they constitute one umbilical vein, which ends in the vena cava, near the right auricle of the heart, and passes through the liver, entering the vena porta; giving off no branches besides until it leaves the convex portion of the liver by a very large orifice. So that if the vena cava is opened from the right auricle downwards and emptied of blood, three apertures may be seen close to each other; one is the entrance of the vena cava descendens, the second that of the hepatic vein, which ramifies throughout the convex portion of the liver, and the third is the origin of the umbilical vein. Hence it is quite clear that the origin of the veins is by no means to be looked for in the liver; inasmuch as the orifice of the vena cava descendens is much larger than the hepatic branch, which is indeed equalled in size by the umbilical vein. For the branches are not said to be the origin of their trunk; but where the trunk is greatest there the origin of the veins is to be looked for, and this is the case at the entrance of the right ventricle: here, then, the origin of all veins, and the storehouse of the blood must be placed.
To return to the umbilical vessels, which are not subdivided in the same way in all animals; for in some two or more branches of veins are found within the body of the fœtus,some of which pass through the liver, whilst others join the portal and mesenteric veins. In the human fœtus, at a distance of three or four fingers' breadth from the umbilicus, the trunks of the arteries and veins are involved together in a complicated manner, (as if one were to twist several waxen tapers in the form of a stick,) and are besides covered and held together by a thick gelatinous membrane. This cord passes on towards the chorion, and when arrived at the concave portion of the placenta and the inner surface of the chorion, splits into innumerable branches; these divide again, and constitute ​the means by which the nutrient matter is taken up, as by rootlets, and distributed to the fœtus. The veins of the cord are marked at various places by knots or varices, resembling vesicles filled with blood; this is a contrivance of nature to prevent the blood rushing too violently to the fœtus. From the number of these knots superstitious midwives are accustomed to predict the number of the future offspring; and if none can be seen at all they pronounce that the woman will be ever after barren: they also absurdly prophesy by the distance between the knots about the interval to take place between the birth of each child, and also of its sex from their colour.
A like arrangement of the umbilical vessels is found in almost all fœtuses furnished with a single placenta, as in the dog, mouse, and others; but in these the cord is shorter and less convoluted. In the ox, sheep, red-deer, fallow-deer, hog, and others, in which the nutrient material is not supplied from one fleshy mass or placenta, but from several, the umbilical vessels are distributed in a different manner. The branches and extremities of these vessels are not only disseminated through the fleshy substance, but still more and chiefly through the membrane of the chorion itself by means of the most delicate fibres; exactly in the same way as the vessels are distributed in the human fœtus, without the aid of the cord, before the "conception" adheres to the uterus. Hence it is plain that the embryo does not derive all its nourishment from the placenta, but receives a considerable portion of it from the fluid contained in the chorion.
As to the uses of the umbilical vessels, I cannot agree with Fabricius, for he imagines that all the blood is supplied to the fœtus from the uterus by means of the veins, and that the vital spirits are transmitted from the mother by the arteries. He also asserts that no part of the fœtus performs any common function, but that each individual portion looks only to itself, how it may be nourished, grow, and be preserved. In like manner, because he has found no nerve in the umbilical cord, he refuses to allow sensation or voluntary motion to the fœtus. Just as if the uterus or placenta of the mother were the heart or first source whence these functions are derived to the fœtus, and whence heat flows in and is distributed through all its parts. All these are manifest errors. For the human fœtus, even ​before the completion of the fourth month, (in some animals sooner,) in no obscure manner moves, rolls about, and kicks, especially if it suffer from cold, heat, or any external source of inconvenience. Moreover, the "punctum saliens" (whilst yet the heart is not) moves to and fro, with an evident pulsation, and distributes blood and spirits; and this part, as I have before stated, if languid and nearly extinct through cold, will, if warmth be applied, again be restored and live. In the Cæsarean section, also, it is quite clear that the life of the embryo does not immediately depend upon the mother, and that the spirits do not proceed from her; for I have often seen the fœtus extracted alive from the uterus when the mother has been dead some hours. I have also known the rabbit and hare survive when extracted from the uterus of the dead mother. Besides, in a tedious labour we learn whether the infant is alive or not by the pulsation of the umbilical arteries; and it is certain that these arteries receive their impulse from the heart of the fœtus and not of the mother, for the rhythm of the two differs: this can be easily ascertained if one hand is applied to the wrist of the mother and the other to the umbilical cord. Nay, in the Cæsarean section, when the embryo is still enveloped in the chorion, I have often found the umbilical arteries pulsating, and the fœtus lively, even when the mother was dead and her limbs stiffened. It is not, therefore, true that the "spirits" pass from the mother to the fœtus through the arteries; nor is it more so that the umbilical or fœtal vessels anastomose with those of the uterus. The fœtus has a proper life of its own, and possesses pulsating arteries filled with blood and "spirits," long before the "conception," in which it is formed and dwells, is attached to the uterus; just as it is with the chick in the egg.
In my treatise on the Circulation of the Blood I have shown the uses of the arteries, both in the fœtus and in the adult, to be very different from what is generally supposed, and my views receive confirmation from the subject now under consideration.
In truth, the "secundines" are part of the "conception," and depend upon it, borrowing thence their life and faculty of growth. For, just as in the mesentery, the blood is propelled to the intestines by the branches of the cœliac and mesenteric ​arteries, and returns thence by means of the veins to the liver and heart, together with the chyle, so in like manner do the umbilical arteries carry the blood to the secundines; which blood, together with the nutrient fluid, is brought back by the veins to the fœtus. Hence it is that these arteries do not proceed immediately from the heart, as if they were the principal vessels, but take their origin from the arteries of the lower limbs, as being of inferior rank, use, and magnitude.
Adrian Spigelius lately published a book entitled 'On the Formation of the Fœtus' (de Formato Fœtu); in which he treats of the uses of the umbilical arteries, and proves, by powerful arguments, that the fœtus does not receive vital spirits" from the mother through the arteries; he also answers fully the arguments on the other side. He could also have shown by the same arguments that neither is the blood transferred to the fœtus from the vessels of the mother by means of the branches of the umbilical veins; this is especially clear from the case of the hen's egg, and also of the Cæsarean section. In truth, if heat and life flow to the blood from the mother, should she die the child must straightway be destroyed also, for the same fatality must attach to both; nay, the child must be the first to perish; for as dissolution approaches, the subordinate parts languish and grow chill before the principal ones, and so the heart fails last of all. The blood, I mean of the fœtus, would be the first to lose its heat and become unfit to perform its functions were it derived from the uterus, since the uterus would be deprived of all vital heat before the heart.
* ↑ Lib. de Form. Fœt. cap. 1.
* ↑ Cap. i.
* ↑ Cap. v.
* ↑ De Gen. Anim. lib. iii, cap. 9.
* ↑ Ibid.
* ↑ Hist. Anim. lib. vii, cap. 7.
* ↑ Hist. Anim. lib. vii, cap. 7.
* ↑ Cap. iii.
* ↑ 5 Aphor. xlv.
* ↑ Lib. de Dissect. Uteri, cap. ult.
* ↑ Cap. iii.
* ↑ De Form. Fœt. p. 122.
* ↑ Cap. iv.
* ↑ Hist. Anim. lib. vii, cap. 8.
* ↑ Op. cit. cap. 2.