ÜBER DIE ENTWICKLUNG DER SCHWEINEPLACENTA

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Abstract
Eight stages from the 2-cm. embryo to the afterbirth are carefully descr. Care was taken to preserve the natural close apposition of the chorion to the endometrium. This is shown to be very intimate, fine protoplasmic processes of the trophoblastic cells penetrating between the uterine epithelial cells. The only remnants of the uterine cavity are the areolae. Three distinct placental situations are recognized (1) areolae, where secretion of uterine glands (histiotroph) is absorbed by the lining epithelium of the areolar cavity, (2) epithelial arcades between the bases of the villi and also at the bases of their branches, where hemotrophic transfer of foodstuffs is believed to occur, and (3) the tips and sides of the villi where the chorionic capillaries penetrate into the trophoblast and the latter persists between the fetal endo-thelium and the maternal epithelium only as extremely thin protoplasmic plates. These are believed to be the areas of respiratory and excretory function. Hitzig believes that Grosser''s designation "epithelio-chorial" for the pig placenta is adequately descriptive only on a morph. basis, not physiologically or phylogenetically. He considers the pig placenta highly specialized, instead of primitive.