THE PLACENTA. 563
��Of the Placenta.
In my opinion, then, the placenta and carunculse 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 foetus alimentary matters which have come from the mother. The mammae 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 fungus- like 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 requi- site 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 foetus nourishment which is puri- fied 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 pre- pared 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, 1 that " this fleshy
1 Cap. iii.
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