A system of obstetrics . >.)»?, remnant of posterior part of prim-itive groove. The anterior divergence of the medullary folds Indicates that portion of themwhich will ultimately give origin to the fore-brain (from Balfour). THE EARLY STAGES OF DEVELOPMENT 111 meet a little way behind the front of the primitive groove. They thenquickly approximate at the region where they formerly spread apart, sothat the neural groove is converted into a narrow trough closed in frontand behind, and bounded by epiblastic elevations on each side. A cross-section of an embryo at this stage, in the region whic
A system of obstetrics . >.)»?, remnant of posterior part of prim-itive groove. The anterior divergence of the medullary folds Indicates that portion of themwhich will ultimately give origin to the fore-brain (from Balfour). THE EARLY STAGES OF DEVELOPMENT 111 meet a little way behind the front of the primitive groove. They thenquickly approximate at the region where they formerly spread apart, sothat the neural groove is converted into a narrow trough closed in frontand behind, and bounded by epiblastic elevations on each side. A cross-section of an embryo at this stage, in the region which isultimately to form the dorsal region of the chick, would show thestructure diagrammatically represented in Fig. 30. Fig. Cross-section of an Embryo in the Dorsal Region soon after the first appearance of the medul-lary folds (diagrammatic): g, medullary groove; in, m, medullary folds; n, notochord; I,peripheral plates of mesoblast; ep, epiblast; h, hypoblast. (The shading of the figure isvery diagrammatic.) In Fig. 31 is represented a later stage of development. The medul-lary folds have risen higher and begun to bend over toward one another. Fig. 31.
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectobstetrics, bookyear1
