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.