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. Quain's elements of anatomy . Fig. Fig. 638.—SUUFACE view of the transparent area of a blastoderm of 18 HOURS, SOMEWHAT diagrammatic (fiom Balfour.) pr, primitive groove, closed in front iiy the coalescence of the two lateral ridges ;one, medullary groove, having on each side the medullary folds or ridges A, which alsomeet in front to enclose the groove, but diverge behind so as to enclose the primitivestreak ; in front the fold of the amnion is commencing. Fi 639.—Area pellucida and DAY. rudiments of the embryo-chick op the second^{ (From IviJlliker.) jpr. primitive streak and groove
. Quain's elements of anatomy . Fig. Fig. 638.—SUUFACE view of the transparent area of a blastoderm of 18 HOURS, SOMEWHAT diagrammatic (fiom Balfour.) pr, primitive groove, closed in front iiy the coalescence of the two lateral ridges ;one, medullary groove, having on each side the medullary folds or ridges A, which alsomeet in front to enclose the groove, but diverge behind so as to enclose the primitivestreak ; in front the fold of the amnion is commencing. Fi 639.—Area pellucida and DAY. rudiments of the embryo-chick op the second^{ (From IviJlliker.) jpr. primitive streak and groove ; Rw, doisal or medullary ridges meeting in front; Rf,medullary groove near its middle ; stz, axial zone ; Pz, parietal zone ; P~\ two vertebralsomites ; Ch, notochord ; Vkf, cephalic fold ; vD, anterior intestinal fold shining through;vAf, anterior or amniotic fold ; Ap, area pellucida. and other organs, together with the extra-embryonic structures, such asthe amnion, yolk-sack and allantois, constituting the coverings of theembryo a
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Keywords: ., boo, bookcentury1800, booksubjectanatomy, booksubjecthumananatomy