. The elements of embryology . Embryology. 320 THE MAMMALIAN EMBEYO. [CHAP. the primitive streak makes its appearance; it is due to a proliferation of rounded cells from the epiblast. Fm. 101. Section through an Oval Blastoderm op a Eabbit on THE Seventh Day. The Length of the Area was ABOUT 1"2 MM. AND ITS BrEADTH ABOUT '86 MM. Through the front part of the primitive streak; ep. epiblast; m. meaoblast; hy. hypoblast; pr. primitive streak. These cells give rise to a part of the mesoblastic layer of the embryo, and may be termed from their origin the primitive streak mesoblast. During
. The elements of embryology . Embryology. 320 THE MAMMALIAN EMBEYO. [CHAP. the primitive streak makes its appearance; it is due to a proliferation of rounded cells from the epiblast. Fm. 101. Section through an Oval Blastoderm op a Eabbit on THE Seventh Day. The Length of the Area was ABOUT 1"2 MM. AND ITS BrEADTH ABOUT '86 MM. Through the front part of the primitive streak; ep. epiblast; m. meaoblast; hy. hypoblast; pr. primitive streak. These cells give rise to a part of the mesoblastic layer of the embryo, and may be termed from their origin the primitive streak mesoblast. During the seventh day the primitive streak be- comes a more pronounced structure (Fig. 101), the mesoblast in its neighbourhood increases in quantity, while an axial groove (Fig. 100)—the primitive groove —is formed on its upper surface. The formation of the medullary groove. In the part of the embryonic area in front of the primitive streak there arise during the eighth day two folds bounding a shallow median groove, which meet in front, but diverge behind, and enclose between them the foremost end of the primitive streak (Fig. 103). These folds are the medullary folds and they constitute the first definite traces of the embryo. The medullary plate bounded by them rapidly grows in length, the primitive streak always remaining at its hinder end. While the. 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 Foster, M. (Michael), Sir, 1836-1907; Balfour, Francis M. (Francis Maitland), 1851-1882; Sedgwick, Adam, 1854-1913; Heape, Walter, 1855-1929. London ; New York : Macmillan
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Keywords: ., bookcentury1800, bookdecade1880, bookpubli, booksubjectembryology
