. A text-book of comparative physiology for students and practitioners of comparative (veterinary) medicine . Fig. 89.—Human embryo, twelve weeks old, with its coverings; natural size. Thenavel-cord passes from the navel to the placenta, b, amnion; c, chorion; d, pla-centa; d, remains of tufts on the smooth chorion; /. decidua reflexa (inner); g,decidua vera (outer). (Haeckel after Bernhard Schultze.) this fusion of several, is of a low type of structure, the result ofgradual degeneration, as the role they once played was takenup by the other parts. But of paramount importance is the formation
. A text-book of comparative physiology for students and practitioners of comparative (veterinary) medicine . Fig. 89.—Human embryo, twelve weeks old, with its coverings; natural size. Thenavel-cord passes from the navel to the placenta, b, amnion; c, chorion; d, pla-centa; d, remains of tufts on the smooth chorion; /. decidua reflexa (inner); g,decidua vera (outer). (Haeckel after Bernhard Schultze.) this fusion of several, is of a low type of structure, the result ofgradual degeneration, as the role they once played was takenup by the other parts. But of paramount importance is the formation of the pla-centa. The chorion ceases to be vascular except at the spot atwhich the villi not only remain, but become more vascular andbranch into arborescent forms of considerable complexity. Itis discoidal in form, made up of a fcetal part just described anda maternal part, the decidua serotina, the two becoming blended COMPARATIVE PHYSIOLOGY. so that the removal of one involves that of more or less of theothers. The connection of parts is far closer than that described. Fig. 90.—Diagram illustrating the decidua, placenta, etc. (after Liegeois). e, embryo;i, intestine: p, pedicle of the umbilical vesicle; u. v, umbilical vesicle; a, amnion;eh, chorion; v. t, vascular tufts of the chorion, constituting the fcetal portion ofthe placenta; , maternal portion of the placenta; d. v, decidua vera; d. r, de-cidua reflexa; al, allantois. for the rabbit; and, even with the preparation that Naturemakes for the final separation of the placenta from both foetusand mother, this event does not take place without some ruptureof vessels and consequent haemorrhage. It is difficult to conceive of the great vascularity of thehuman placenta without an actual examination of this structureitself, which can be done after being cast off to great advan-tage when floating in water; by which simple method also thethinness and other characteristics of the membranes can bewell made out. The great v
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishernewyo, bookyear1890
