. The elements of Embryology,. -\-:pp C B. D Fig. 9, A io N forms a series of purely cliagrainniatic representations in- troduced to facilitate the comprehension of the manner in which the i)odj' of the embryo is formed, and of the various relations of the yolk-sac, amnion and allaiitois. In all rt is the vitelline membrane, placed, for convenience sake, at some distance from its contents, and represented as persisting in the later stages; in the actual egg it is in direct contact with the blastoderm (or yolk), and early ceases to have a separate existence. In all e indicates the embryo, pp th
. The elements of Embryology,. -\-:pp C B. D Fig. 9, A io N forms a series of purely cliagrainniatic representations in- troduced to facilitate the comprehension of the manner in which the i)odj' of the embryo is formed, and of the various relations of the yolk-sac, amnion and allaiitois. In all rt is the vitelline membrane, placed, for convenience sake, at some distance from its contents, and represented as persisting in the later stages; in the actual egg it is in direct contact with the blastoderm (or yolk), and early ceases to have a separate existence. In all e indicates the embryo, pp the general pleuro-peritoneal space, af the folds of the amnion, a the amnion proper, ae or ac the cavity holding the liquor amnii, al the allantois, a' the alimentary canal, y or ys the yolk or yolk-sac. A, which may be considered as a vertical section taken longitudinally along the axis of the embryo, represents the relations of the parts of the egg at the time of the first appearance of the head-fold, seen on the right-hand side of the blastoderm e. The blastoderm is spreading both behind (to the left hand in the figure), and in front (to right hand) of the head-fold, its limits being indicated by the shading and thickening for a certain distance of the margin of the yolk y. As yet there is no fold on the left side of e correspond- ing to the head-fold on the right, while therefore the front limit of the embryo, as distinguished from the blastoderm, is marked out by the head-fold, there is at present no tail-fold, and therefore no hind limit. 5 is a vertical transverse s-ction of the same period drawn for convenience sake on a larger scale (it should have been made flatter and less curved). It shews that the blastoderm (vertically shaded) is extending laterally as well as fore and aft, in fact in all directions; but there are no lateral folds, and there-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability
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Keywords: ., bookcentury1800, bookdecade1870, bookpublisherlondo, bookyear1874
