A system of obstetrics . ry of Haddon and Minot be accepted, the blastodermicvesicle must be regarded as a mere survival from a time when a food- THE EARLY STAGES OF DEVELOPMENT. 125 yelk was present in all mammalian eggs. In the now-existing highermammals it contains no yelk, but becomes filled and distended by analbuminous liquid absorbed from the ute-rine mucous membrane. The Development of the Foetal Membranesand Appendages of the Mammal,1 while inessentials similar to that of the bird, pre-sents certain differences which we must nowconsider. These arc, in part, due to therelatively small
A system of obstetrics . ry of Haddon and Minot be accepted, the blastodermicvesicle must be regarded as a mere survival from a time when a food- THE EARLY STAGES OF DEVELOPMENT. 125 yelk was present in all mammalian eggs. In the now-existing highermammals it contains no yelk, but becomes filled and distended by analbuminous liquid absorbed from the ute-rine mucous membrane. The Development of the Foetal Membranesand Appendages of the Mammal,1 while inessentials similar to that of the bird, pre-sents certain differences which we must nowconsider. These arc, in part, due to therelatively small size and trivial import-ance of the mammalian yelk-sac, and toits very early completion and subsequentrapid shrinkage. From Fig. 50 may begained some idea as to the relative extentof the embryonic and non-embryonic areasof the rabbits oosperm at a stage shortlyafter the formation of the mesoblast in theembryonic region, and when the hypoblasthas spread beyond that region aud halfway around the embryonic vesicle. Fig. Longitudinal Section of MammalianEmbryo when the hypoblast isabout halfway round the blasto-dermic vesicle: a, (i, anterior andposterior ends of embryonic area;zp, zona pellucida; ep, epiblast; hy,hypoblast, me, mesoblast; , cav-ity of blastodermic vesicle.
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectobstetrics, bookyear1
