A system of obstetrics . yers. The blasto-dermic bag which thus comes to partiallyenvelop the head is known a- the pro-Offinton,and it still persists for some time after the formation of the amnioticfold- has commenced | /> Fig. 54). It i- subsequently the bird the first mesoblastic clef) and the first amniotic fold occurat the head end of the embryo. In the mammal the reverse ifl the case:when the amniotic tail-fold (Fig. 54, ) is well developed and thepleuroperitonea] cavity and the primitive amniotic cavity (amc) arcconspicuous in the tail region, there is a mere
A system of obstetrics . yers. The blasto-dermic bag which thus comes to partiallyenvelop the head is known a- the pro-Offinton,and it still persists for some time after the formation of the amnioticfold- has commenced | /> Fig. 54). It i- subsequently the bird the first mesoblastic clef) and the first amniotic fold occurat the head end of the embryo. In the mammal the reverse ifl the case:when the amniotic tail-fold (Fig. 54, ) is well developed and thepleuroperitonea] cavity and the primitive amniotic cavity (amc) arcconspicuous in the tail region, there is a mere trace of a pleuroperi-tonea] cavity in front of the head, and a very rudimentary head-foldof the amnion (ahf). Moreover, in the chick (Fig. 40) both layer- of the amniotic foldscontain mesoblast and epiblast ; in the mammal only the inner layer,which is to form the true amnion, possesses any me-oltla-t. At a somewhat later stage (Fig. 55) the true amnion is completed 1 Arch. (/< Biologic, t. v. p. Anaiomu M Embryonal,. Embryonic Area of Rabbit Em-bryo, aged eight days and fourhours from Kolliker; magni-fied 20 diama.): rf, medullarygroove; pr, primitive streak. THE EARLY STAGES OF DEVELOPMENT 127 over the back of the embryo, and the mesoblastic cleft () hasextended back through that portion of the blastoderm which originallyformed the pro-amnion. The false amnion is also seen to have sep-arated to a considerable extent from the blastodermic vesicle, whichhas become reduced in size and covered more than halfway round bymesoblast. Still later (Fig. 56), the false amnion (fa) is seen to have Fig. 54. Fig. 55.
Size: 1224px × 2042px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1880, booksubjectobstetrics, bookyear1
