. The elements of embryology . Embryology. 60 THE FIEST DAY. Fig. 19. [ Transverse Section iHRonsH the Embryonic Region of THE Blastoderm, of a Chick shortly prior to the Formation of the Medullary Groove and Noto- CHORD. m. median line of the section ; ep. epiblast; lower layer cells (primitive hypoblast) not yet completely differentiated into mesoblast and hypoblast; n. nuclei. foldâthe future head-foldânear the front end of the area pellucida. In section (Fig. 20) this opaque line is seen to be due to a special concentration of cells in the form of a cord. This cord is the commen
. The elements of embryology . Embryology. 60 THE FIEST DAY. Fig. 19. [ Transverse Section iHRonsH the Embryonic Region of THE Blastoderm, of a Chick shortly prior to the Formation of the Medullary Groove and Noto- CHORD. m. median line of the section ; ep. epiblast; lower layer cells (primitive hypoblast) not yet completely differentiated into mesoblast and hypoblast; n. nuclei. foldâthe future head-foldânear the front end of the area pellucida. In section (Fig. 20) this opaque line is seen to be due to a special concentration of cells in the form of a cord. This cord is the commencement of an extremely important structure found in all vertebrate embryos, which is known as the notochord {cK). In most instances the commencing notochord remains attached to the hypoblast, after the mesoblast has at the sides become quite detached (m'cZe Fig. 20), but in other cases the notochord appears to become differentiated in the already separated layer of mesoblast. In all cases ike â notochord and the hypoblast below it unite with the front end of the primitive streak; vdth which also the two lateral plates of mesoblast become continuous. From what has just been said it is clear that in the region of the embryo the mesoblast originates as two lateral plates split off from the primitive hypoblast, and. 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
