562 THE MEMBRANES.
however, the fabric of the body is completely formed, the rami- fications 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 foetus.
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 them- selves 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 nou- rished and made to grow.
Wherefore Eabricius 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 be- ginning 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 albu- minous matter without any connexion whatever with the uterus : and thus the foetus is furnished with aliment by the " concep- tion" 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 foetus 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 ex- crementitious matter ; but serves for the support of the foetus. Although, as I have before remarked, it is possible when all the nutrient portions have been taken up, the remainder may de- generate 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 in- numerable shallow pits filled with a muco-albuminous fluid, (a circumstance already observed by Galen 1 ) ; and that from this source the ramifications of the umbilical vessels absorbed the nutriment and carried it to the foetus : 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. 1 Lib. de Dissect. Uteri, cap. ult.
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