. The development of the human body : a manual of human embryology. Embryology; Embryo, Non-Mammalian. THE MEDULLARY GROOVE 67 Fig. 38, A. How this cavity is formed can only be conjectured, but it seems probable that it arises by the splitting of the layer of cells which lines the interior of the trophoblast in the earlier stage (or perhaps by the vacuolization of the central cells of this layer) and the subsequent accumulation of fluid between the two meso- dermal layers so formed. However that may be, it seems clear that the size of the human ovum is due mainly to the rapid growth of this ca
. The development of the human body : a manual of human embryology. Embryology; Embryo, Non-Mammalian. THE MEDULLARY GROOVE 67 Fig. 38, A. How this cavity is formed can only be conjectured, but it seems probable that it arises by the splitting of the layer of cells which lines the interior of the trophoblast in the earlier stage (or perhaps by the vacuolization of the central cells of this layer) and the subsequent accumulation of fluid between the two meso- dermal layers so formed. However that may be, it seems clear that the size of the human ovum is due mainly to the rapid growth of this cavity, which, as future stages show, is the extra-embryonic portion of the body-cavity, the splitting or vacuolization of the. Fig. 38.—Diagrams to show the Probable Relationships of the Parts in the Embryos Represented in Figs. 29, C, and 37. Ac, Amniotic cavity; C, extra-embryonic body-cavity; Me, (in figure to the left) mesoderm, (in figure to the right) somatic mesoderm; Me, splanchnic mesoderm; D, digestive tract; En, endoderm; T, trophoblast. The broken line in the mesoderm of the figure to the left indicates the line along which the splitting of the mesoderm occurs. mesoderm by which it is probably formed being the precocious appearance of the typical splitting of the mesoderm to form the embryonic body-cavity which, as will be seen in a subsequent chap- ter, takes place only at a later stage of development. From now on the trophoblast and the layer of mesoderm lining it may together be spoken of as the chorion, the mesoderm layer being termed the chorionic mesoderm. A little older again than the Peters and Herzog ova are those described by Strahl and Beneke and by von Spee (Embryo v. H.), the chorionic cavity of the former two having an average diameter. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work
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