A system of obstetrics . Diagrammatic Transverse Section through a Hypothetical Mammalian Oosperm, after theprimary layers of the blastoderm had been formed by segmentation of the fertilized i _•food-yelk of the original mammalian ovum is supposed to have been Lost |: a,earlier, and B,later Btage of development; ep, embryonic epiblast; ep, non-embryonic epiblast; yt, cavityof blastodermic vesicle enclosed by non-embryonic epiblast (after Haddon). grow around, has precociously completed the blastodermic vesicle,and the [embryonic portion of the] blastoderm lias sunk into the cavity <»rthe em
A system of obstetrics . Diagrammatic Transverse Section through a Hypothetical Mammalian Oosperm, after theprimary layers of the blastoderm had been formed by segmentation of the fertilized i _•food-yelk of the original mammalian ovum is supposed to have been Lost |: a,earlier, and B,later Btage of development; ep, embryonic epiblast; ep, non-embryonic epiblast; yt, cavityof blastodermic vesicle enclosed by non-embryonic epiblast (after Haddon). grow around, has precociously completed the blastodermic vesicle,and the [embryonic portion of the] blastoderm lias sunk into the cavity <»rthe empty [blastodermic vesicle]. The non-embryonic epiblast then(Fi<r. 49, B) grows over the embryonic area as the cover-cells (p. 104).In this way would arise something very like what we actually find to Fig. Oosperm Of a Rabbit, seven day- after coition. non-embry-onic blastoderm (magnified 10 diameters) (from Kdlliker). occur in the early stages of the development of the rabbit (Figs, L6 and17) and some other higher mammals. [f the theory 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 toit
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectobstetrics, bookyear1
