. A text-book of comparative physiology [microform] : for students and practitioners of comparative (veterinary) medicine. Physiology, Comparative; Veterinary physiology; Physiologie comparée; Physiologie vétérinaire. 78 COMPARATIVE PHYSIOLOGY. TBB iHBTAXi (BMBRTONIO) MBBIBIUNBS OF. The differences between the development of the eggf mem- branes of iTii^mmftl* and birds are chiefly such as result from the absence in the '^ • ^ former of an eggnshell and its membranes, and of yelk and albumen. The mammalian orum is inclosed by a zona radiata (zona peUuci- da) surrounded by an- other very delica
. A text-book of comparative physiology [microform] : for students and practitioners of comparative (veterinary) medicine. Physiology, Comparative; Veterinary physiology; Physiologie comparée; Physiologie vétérinaire. 78 COMPARATIVE PHYSIOLOGY. TBB iHBTAXi (BMBRTONIO) MBBIBIUNBS OF. The differences between the development of the eggf mem- branes of iTii^mmftl* and birds are chiefly such as result from the absence in the '^ • ^ former of an eggnshell and its membranes, and of yelk and albumen. The mammalian orum is inclosed by a zona radiata (zona peUuci- da) surrounded by an- other very delicate cov- ering {vitettine mem- brane). The growth of the bkutodermic vesicle (yelk-sac) is rapid, and, being filled with fluid, the zona is thinned and soon disappears. The germinal area alone is made up of three layers of cells (Fig. 100), the rest of the upper part of the oSsperm being lined witii epiblast and hyp- oblast, while the low- er zone of the yelk-sac consists of epiblast only. Simple, non-vascular villi, serving to attach the embryo to the uterine walls, usually project from the epiblast of the subzonal membrane. In the rabbit they do not occur every- where, but only in that region of the epiblast beneath which the mesoblast does not extend, with the exception of a patch which soon appears and demarkates the site of the future plar centa. The amnion and allantois are formed in much the same way as has been described for the chick. At about the same period as these events are transpiring the vascular yelk-sac has become smaller, and the allantois with its abundant supply of blood-vessels is becoming more promi- Fio. 79. —DUgnunoutlc lonxitndtnal Mction of oOspenn of rabbit at an advanced itaRe of prec- nancy (KAIIiker, after Biacholt). a, amnion; <u, •llantoiR with iU blood-veHela; «, embirp; (b. yelk-aae; €d, «d', td", hypoblaatic cplthelinm of the vellc-Mc and its atalk (ambllical veaiele and cord); /d. vaicniar meiobUiatic membrane of the nmbt
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Keywords: ., bookauthormillswes, bookcentury1800, bookdecade1890, bookyear1890
