A system of obstetrics . 2centi-meters); it become- gradually attenuated toward the margin, which is 1 The placenta of Rodentia, rnsectivora, and Cheiroptera is also disooidal in term,hui differs in several important respects, as regards development, from that of manand apes. Comparative embryologists reserve the name disooidal tor the rodent name the human type meta-discoida! 8 I sterand Balfour, Elements of Embry-ology, p. 363 et THE EARLY STAGES OF DEVELOPMENT. 137 slightly rounded, measuring here only 2-4 lines (4-7 millimeters) inthickness (Farre). At its margins it is continuous
A system of obstetrics . 2centi-meters); it become- gradually attenuated toward the margin, which is 1 The placenta of Rodentia, rnsectivora, and Cheiroptera is also disooidal in term,hui differs in several important respects, as regards development, from that of manand apes. Comparative embryologists reserve the name disooidal tor the rodent name the human type meta-discoida! 8 I sterand Balfour, Elements of Embry-ology, p. 363 et THE EARLY STAGES OF DEVELOPMENT. 137 slightly rounded, measuring here only 2-4 lines (4-7 millimeters) inthickness (Farre). At its margins it is continuous with both thedecidua vera and the decidua reflexa (Figs. 61 and 64). The amniotic sheath of the umbilical cord is shown in Figs. 57 and60 as having extended a considerable distance along the allantoic stalk,but as not yet having reached the inner surface of the chorion. Thisit ultimately does, and the amnion then spreads out on all sides overthe chorion frondosum, and, adhering closely to it, forms the inner or Fig. Vertical Section of Uterus, with placenta attached (from a woman in the thirtieth week of ges-tation ; from Farre, after Wagner). The lines uu indicate the thickness of the uterine walloutside the decidua serotina; dp, the decidua serotina, or placenta; p, the thickness of therest of the placenta (toward the right of the figure the serotina is separated into rtd. uterineserotina. and <lp, decidual serotina, with its septa passing up among the chorionic villi); /,umbilical cord; am, amnion; ch, chorion : vf, total blood-vessel on surface of placenta cutacross; it, chorionic villi; us and «, dilated uterine blood-vessels. foetal surface of the placenta. At the margins of the placenta it turnsback to envelop the embryo. A section through the placenta (Fig. 63)therefore shows the amnion (am) as forming its innermost layer, [mmediately external to the amniotic layer comes the chorion (ch),from whose outer surface the very numerous, greatly-branched, tortuousvil
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectobstetrics, bookyear1
