EXERCISE THE SEVENTIETH.
Of the conception of the deer in the course of the month of December.
In the beginning of December the fœtus is seen larger, every way more perfect, and the length of the finger. The heart and other viscera which formerly hung externally are now concealed within the cavities of the body, so that they can no longer be seen without dissection.
The conception, or ovum, by the medium of the five caruncles which we have already spoken of as present in either cornu, is now in connexion with the uterus at an equal number of points; still the union is not so strong but that a very slight rather than a great effort suffices to break it. When the conception is detached, we perceive points or depressions on the surface of the chorion at the places where the adhesions to the uterus had existed, these spots being further covered with a certain viscid and wrinkled matter, as if this had been the bond of union between the mother and the ovum. Thus have we the nature and use of these caruncles made known to us: seen in the first instance as fungi or excrescences growing from the sides of the uterus, they are now recognized in connexion with the conception, as standing instead of the placenta or uterine cake in the human subject, and performing the same office. These caruncles are in fact but as so many nipples, whence the embryo by means of its umbilical vessels receives the nourishment that is supplied by the mother, as shall be clearly shown by what is to follow.
The size and capacity of the uterus, by which name we understand the cornua, or place occupied by the conception, is increased in proportion to the growth of the embryo; in suchwise, however, that the horn in which the fœtus is lodged is larger than the other.
The conception or ovum is single, whether one or several embryos are evolved from it; and it extends, as already said, into both of the horns, so that it presents itself with the shape of a double pudding, or rather of a single pudding having a constriction in its middle. Proceeding rounded and slender from the upper extremity of one of the horns, the conception gradually enlarges, and is produced into that common cavity which in the human female is called the uterus or matrix; (because, by conceiving and cherishing her offspring in this place the woman is made a mother;) the conception of the deer, passing through a kind of isthmus in the body of the uterus, is narrowed; but by and by, escaping into the other cornu, it there expands at first, but anon contracts again, and finally ends as it began in a tapering extremity. The whole conception, therefore, taken out entire, resembles a wallet filled with water on either side; and hence the chorion is also called allantois, because the conception in the lower animals, such as the deer, looks like an intestine inflated, or stuffed and tied in the middle.
In the embryo anatomized at this period every internal part is seen distinct and perfect; particularly the stomach, intestines, heart, kidneys, and lungs, which, divided into lobes, but having the proper form of the organs, look bloody. The colour of the lungs is deeper than it is in those fœtuses that have breathed, because the lungs, dilated by the act of respiration, assume a whiter tint. And by this indication is it known whether a mother has brought forth a living or dead child; in the former case the colour of the lungs is changed, and the change remains though the infant have died immediately afterwards.
In the female fœtus the testes—improperly so called—are seen situated near the kidneys at the extremities of the cornua uteri on either side; they are relatively of larger size than in the adult, and, like the caruncles of the uterus, look white.
In the stomach of the fœtus there is a watery fluid contained, not unlike that in which it swims, but somewhat more turbid or less transparent. It resembles the milk that begins to be secreted in the breasts of pregnant women about the fourth or fifth month of pregnancy, and may be pressed out of the nipples, or it is like the drink which we call white posset.
In the small intestines there is an abundance of chyle concocted from the same matter; in the colon greenish fæces and scybala begin to appear.
I do not find the urachus perforate; neither do I perceive any difference between the tunica allantoides or allantois, which is said to contain urine, and the chorion. Neither do I detect any urine in the secundines, but only in the bladder, where indeed it is present in large quantity. The bladder, of an oblong form, is situated between the umbilical arteries as they proceed from the bifurcation of the descending aorta.
The liver is rudely sketched and almost shapeless, as if it were a mere accidental part; it looks like a red coloured mass of extravasated blood. The brain, with some pretensions to regularity of outline, is contained within the dura mater. The eyes are concealed under the eyelids, which are as firmly glued together as we find them in puppies for some short time after birth, so that I found it scarcely possible to separate them and open the eyes. The breast-bones and ribs have a certain degree of firmness, and the colour of the muscles changes from white to blood red.
By the great number of dissections which I performed in the course of this month, I was every day confirmed in my opinion that the carunculæ of the uterus perform the office of the placenta; they are at this time found of a reddish colour, turgid, and of the size of walnuts. The conception, which had previously adhered to the caruncles by the medium of mucor or glutinous matter only, now sends the branches of its umbilical vessels into them, as plants send their roots into the ground, by which it is fastened and may be said to grow to the uterus.
About the end of December the fœtus is a span long, and I have seen it moving lustily and kicking; opening and shutting its mouth; the heart, inclosed in the pericardium, when exposed, was found pulsating strongly and visibly; its ventricles, however, were still uniform, of equal amplitude of cavity and thickness of parietes; and each ending in a separate apex, they form together a double-pointed cone. Occasionally I have seen the fluid contained in the auricles of the heart, which at this time present themselves as ample sacs filled with blood, continuing to pulsate for some short time after the ventricles themselves had left off contracting.
The internal organs, all of which had lately become perfect, were now larger and more conspicuous. The skull was partly cartilaginous, partly osseous. The hooves were yellowish, flexible, and soft, resembling those of the adult animal softened in hot water. The uterine caruncles, of great magnitude and like immense fungi, extended over the whole cavity of the uterus, and plainly performed the office of placentæ, for numerous and ample branches of the umbilical vessels penetrated their substance there to imbibe nutritive matter for the growth of the embryo. As in the fœtus after birth, the chyle is now carried by the mesenteric veins to the porta of the liver.
Where there is a single fœtus the umbilical vessels are distributed to the whole of the carunculse, both those of the horn where the fœtus is lodged and those of the opposite horn; where there is a pair of embryos formed, the umbilical vessels of each only extend to the caruncles of the horn appropriated to it.
The smaller umbilical veins in tending towards the fœtus, form larger and larger trunks by coalescing, until at length two great canals are formed, which in conjunction pour their blood into the vena cava and vena portæ. But the umbilical arteries, which arise from the division of the descending aorta, form two trunks of small size, not remarkable save for their pulse: proceeding to the boundary of the conception, in other words, to the conjunction of the placenta or carunculæ with the ramifications of the umbilical veins, they first divide into numerous capillary twigs, and then are lost in others that are invisible.
As the extremities of the umbilical veins within the uterus terminate in the caruncles, so the uterine vessels on the outside, which are large and numerous, and bring the blood from the mother towards the uterus, by means of the vessels of the suspensory ligaments, terminate externally on the caruncles. It is to be noted, also, that the internal vessels are almost all veins; the external vessels, again, are in many instances branches of arteries. In the placenta of the woman, if it be carefully examined immediately after delivery, a much larger number of arteries than of veins, and these of larger size, will be found dispersed on every side in innumerable subdivisions to the very edge of the mass. In the same kind of spongy parenchyma of the spleen, the number of the arteries is also greater than that of the veins.
The exterior uterine vessels run to the uterus, as I have said, not to the ovaries (testiculi) situated in the suspensory ligament, as some suppose.
I have remarked an admirable instance of the skill of nature, in the bulge or convexity of the caruncles turned towards the conception: a quantity of white and mucilaginous matter is discovered in a number of cavities, cotyledons, or little cups; these are all as full of this matter as we ever see waxen cells full of honey; now this matter, in colour, consistency, and taste, is extremely like white of egg. On tearing the conception away from the caruncles, you will perceive numbers of suckers or capillary branches of the umbilical veins, looking like lengthened filaments, extracted at the same time from every one of the cotyledons and pits, and from amidst their mucilaginous contents; very much as we see the delicate filaments of the roots of herbs following the stem when it is pulled out of the ground.
It is clearly ascertained from this that the extremities of the umbilical vessels are not conjoined by any anastomosis with the extremities of the uterine vessels; that they do not imbibe any blood from them, but that they end and are obliterated in that mucilaginous matter, and from it take up their nourishment, nearly in the same way as at an earlier period they had sought for aliment from the albuminous humour contained within the membranes of the conception. In the same manner, consequently, as the chick in ovo is nourished by the white of the egg through its umbilical vessels, is the fœtus of the hind and doe nourished by a similar albuminous matter laid up in these cells, and not directly from the blood of the mother.
These carunculæ might therefore with propriety be called the uterine liver, or the uterine mammæ, seeing that they are organs adapted for the preparation and concoction of that albuminous aliment, and fitting it for absorption by the veins. In those viviparous animals consequently that have neither caruncles nor placentæ, as the horse and the hog, the fœtus is nourished up to the moment of its birth by fluids contained within the conception or ovum; nor has the ovum in these animals at any time a connexion with the uterus.
From all of what precedes it is manifest that in both the classes of viviparous animals alluded to, those, namely, that are provided with carunculæ or cotyledons, and those that want them, and perhaps in viviparous animals generally, the fœtus in utero is not nourished otherwise than the chick in ovo; the nutritive matter, the albumen, being of the same identical kind in all. As in the egg the terminations of the umbilical vessels are in the white and yelk, so in the hind and doe, and other animals furnished with uterine cotyledons like them, the final distributions of the umbilical vessels are sent to the humours that are included within the conception or ovum, and to the albumen that is stored in the cotyledons, or cup-like cavities of the carunculæ, where they open and end. And this is further obvious from the fact of the extremities of the umbilical vessels, when they are drawn out of the afore-mentioned mucor, looking completely white; a certain proof that they absorb this mucilage liquefied only, and not blood. The same arrangement may very readily be observed to obtain in the egg.
The human placenta is rendered uneven on its convex surface, and where it adheres to the uterus, by a number of tuberous projections, and it seems indeed to adhere to the uterus by means of these; it is not consequently attached at every point, but at those places only where the vessels pierce it in search of nourishment, and at those where, in consequence of this arrangement, an appearance as if of vessels broken short off is perceived. But whether the extremities of these vessels suck up blood from the uterus, or rather a certain concocted matter of the nature of albumen, as I have described the thing in the hind and doe, I have not yet ascertained.
Finally, that the truth just announced may be still more fully confirmed, it is found that by compressing the uterine caruncles between the fingers, about a spoonful of the nutritive fluid in question may be obtained from each of them, as from a nipple, unmixed with blood, which is not obtained even with forcible pressure. Moreover, the caruncle thus milked and emptied, like a compressed sponge, contracts and becomes flaccid, and is seen to be pierced with a great number of holes. From everything, therefore, it appears that these caruncles are uterine mammæ, or fountains and receptacles of nutritive albumen.
The month of December at an end, the caruncles adhere less firmly to the uterus than before, and a small matter suffices to detach them. The larger the fœtus grows, indeed, the nearer it is to its term, the more readily are the caruncles detached from the uterus, so that, like ripe fruit from the tree, they slip at length from the uterus of themselves, and as if they had formed an original element in the conception.
Separated from the uterus you may perceive in the prints which they leave points pouring out blood; these are the arteries that entered them. But if you now detach the conception from the caruncles, no blood is effused; none escapes, save from the ends of the vessels proceeding from the conception, although it does seem more consonant with reason to suppose that blood should be shed from the caruncles than from the conception when they are forcibly separated. For, as the caruncles or cotyledons have an abundance of uterine branches distributed to them, and they are generally believed to receive blood for the nourishment of the fœtus, we should expect that they would appear replete with blood. Nevertheless, as I have said, they yield no blood either under milking or compression, and the reason of this is that they contain albumen rather than blood, and rather store up than prepare this matter. It seems manifest, therefore, that the fœtus in utero is not nourished by its mother’s blood, but by this albuminous fluid duly elaborated. It may even be perhaps that the adult animal is not nourished immediately by the blood, but rather by something mixed with the blood, which serves as the ultimate aliment; as may perhaps be more particularly shown in our Physiology and particular treatise on the Blood.
The truth of that passage of Hippocrates[342] where it said that “those whose acetabula or cotyledons are full of mucor, abort,” has always been suspected by me; for this is no excrementitious matter or cause of miscarriage, but nourishment and a source of life. But Hippocrates, by the word acetabula, perhaps, understood something else than the parts so called in the uterus of the lower animals, for they are wanting in women; nor does the placenta in the human subject contain any collections of albuminous matter in distinct cavities.
Modern medical writers, following the Arabians, speak of three nutritious humours—dew, gluten, and cambium; these Fernelius designates nutritious juices; as if he had wished to imply that the parts of our bodies were not immediately nourished by the blood as ultimate nutriment, but by these secondary juices. The first of them, like dew, bathes all the minutest particles of the body on every side: this fluid, become thicker by an ulterior concoction, and adhering to the parts, is called gluten; finally, altered and assimilated by the proper virtue of the part, it is called cambium.
He who espoused such views might designate the matter which is contained in the cotyledonous cavities of the deer as gluten or nutritious albumen, and maintain that as the ultimate nourishment destined for each of the particular parts of the fœtus it was analogous to the albumen or vitellus of the egg. For as we but lately stated, with Aristotle, that the yelk of the egg was analogous to milk, so do we think it not unreasonable to assert, that the matter lodged in the cotyledons, or acetabula of the uterine placenta, stands instead of milk to the fœtus so long as it remains in the uterus; in this way the caruncles approve themselves a kind of internal mammæ, the nutritive matter of which, transferred at the period of parturition to the proper mammæ, there assumes the nature of milk, an arrangement by which the fœtus is seen to be nourished with the same food after it has begun its independent existence, as it was whilst it lodged in the uterus. Between the two-coloured eggs of oviparous animals, consequently, or the eggs that consist of a white and a yelk, and the ova or conceptions of viviparous animals, there is only this difference, that in the former the vitellus (which is a secondary nutritive matter) is prepared within the egg, and at the period of birth, being stored within the abdomen of the young creature, serves it as food; whilst in the latter, the nutritive juice is laid up within acetabula, and after birth is transferred to the mammæ; so that the chick is nourished with milk inclosed in its interior, whilst the fœtus of the viviparous animal draws its nourishment from the breasts of its mother.
In the months of January, February, &c., as nothing new or worthy of note occurs which has not been already mentioned, (more than the growth of the hair, teeth, horns, &c.) but the parts only grow larger without reference to the process of generation, it seems unnecessary to say more upon such points at present.
I have frequently examined the conceptions of sheep during the same intervals. These I find, as in the deer, extending into both horns of the uterus, and presenting the figure of a wallet or double sausage. In several of them I found two fœtuses; in others only one: they were without a trace of wool on the surface, and the eyelids were so closely glued together that they could not be opened; the hooves, however, were present. Where there were two embryos they were contained in the opposite horns of the uterus, and without any regard to sex with reference to the right or left horn, the male being sometimes in the right, sometimes in the left, and the female the same; both, however, were, in every instance, included within one and the same common external membrane or chorion. The extreme ends of this membrane were stained on either hand with a yellow or bilious excrement, and appeared to contain something turbid or excrementitious in their interior.
Many caruncles, or miniature placentas of different sizes, were discovered, and otherwise disposed than in the hind and doe. In the sheep they look like rounded fungi with the foot-stalks broken off, and are contained in the coats of the uterus; their rounded or convex aspects are turned to the uterus, (a circumstance, by the way, common to the cow and sheep,) their concave aspects, which are the smooth ones, being turned towards the fœtus. The larger branches of the vessels are also distributed to the concave portion, as in the human placenta. The branches in extension of the umbilical vessels connected with the caruncles, grow pretty firmly into them, so that when I attempted to separate them the rounded portion was rather torn from the interior of the uterus than from the ovum or conception; different, consequently, from what we observed in the deer, where the chorion was readily detached from the cotyledons of the caruncules, and where the convexity of the caruncule, connected with the conception, is separable, whilst the concavity, or rather the pedicle or root, is firmly adherent to the uterus. In other respects the function seems to be the same in both cases; in both the same acetabula are discovered, and the same viscid and albuminous mucus can be pressed out in both, as it can also in the cow.
In the conception that contains a single fœtus, the umbilical vessels are distributed to the whole of the caruncules of either horn; but the one in which the fœtus itself is contained, swimming in its crystalline fluid within the amnion, is larger than the other. In the cases where there are two fœtuses present, each has its own separate or appropriate caruncles, and does not send its umbilical vessels in quest of nourishment beyond the cornu in which it is lodged.
In male fœtuses, the testes contained in the scrotum, of large size for the age, hang externally. Female fœtuses, again, have their dugs in the same situation, furnished with nipples like the breasts of women.
In the compound stomach of the fœtus, namely the omasus and abomasus, a clear fluid is discovered, similar to that in which it floats; the two liquids agreeing obviously in smell, taste, and consistency. There is also a quantity of chyle in the upper part of the intestinal tube; in the inferior portion a greenish-coloured excrement and scybala, such as we find when the animal is feeding on grass. The liver is discovered of considerable size, the gall-bladder of an oblong shape, and in some cases empty.
In so far as the order in which the several parts are produced is concerned, we have still found the same rule to be observed in the hind and doe as in the egg, and we believe that the same law obtains among viviparous animals generally.