Veterinary obstetrics, including the diseases of breeding animals and of the new-born . ot persist, but soon atrophies andalmost wholly vanishes long before birth. The formation of theallantois follows more or less the plan of the blastoderm and itsyolk sac and in these animals becomes much elongated. Inswine the apices of the allantoic .sac are destitute of placental The Chorion 357 tufts, as shown in Fig. 77. In ruminants, Fig. 80, the allantoicsac becomes much elongated, while its apex, along with theamniotic chorion, finally undergoes necrosis, as shown on theright of the figure, or the ap
Veterinary obstetrics, including the diseases of breeding animals and of the new-born . ot persist, but soon atrophies andalmost wholly vanishes long before birth. The formation of theallantois follows more or less the plan of the blastoderm and itsyolk sac and in these animals becomes much elongated. Inswine the apices of the allantoic .sac are destitute of placental The Chorion 357 tufts, as shown in Fig. 77. In ruminants, Fig. 80, the allantoicsac becomes much elongated, while its apex, along with theamniotic chorion, finally undergoes necrosis, as shown on theright of the figure, or the apex of the amniotic chorion alone be-comes necrotic without the allantois having penetrated it, asshown at the left. In case of single pregnancy, the allantoic sac of the ruminantoccupies both cornua. The arrangement of the allantois inruminants differs greatly from that of the horse. The allantoicsac does not completely surround the fetus but. lying along itsventral side, greatly elongated, only partially encloses the amnion. Amnion Epithelial Thickeningsof the Amnion miotic Chorion. Innery Layer Hippotnanes, Jfippomanes Fig. 75. Schematic longitudinal section of a horse embryo in its annexes, at about 5 mos. gestation. Reduced to about >i. (Bonnet). This applies, however, only to the inner or hypoblastic layer ofthe allantois, which constitutes the immediate wall of the vascular, or mesoblastic, laj-er extends completely aroundthe fetus and its amnion but, over that portion of the amnionwhere the allantoic sac does not extend, the amnion, vascularlayer of the allantois and amniotic chorion are unseparated by 358 Veterinarv Obstetrics
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