. The development of the chick; an introduction to embryology. Birds -- Embryology. 186 THE DEVELOPMENT OF THE CHICK (Fig. 107) the primitive relations of the parts are still preserved. In the twenty-sixth somite (Fig. 108) it will be seen that the cells of the core and of the ventral and median wall of the somite extending from the nephrotome to about the center of the neural tube are becoming mesenchymal; they spread out towards the notochord and the space between the latter and the dorsal aorta. These cells constitute the sclerotome. The muscle plate extends from the dorsal edge of the scle
. The development of the chick; an introduction to embryology. Birds -- Embryology. 186 THE DEVELOPMENT OF THE CHICK (Fig. 107) the primitive relations of the parts are still preserved. In the twenty-sixth somite (Fig. 108) it will be seen that the cells of the core and of the ventral and median wall of the somite extending from the nephrotome to about the center of the neural tube are becoming mesenchymal; they spread out towards the notochord and the space between the latter and the dorsal aorta. These cells constitute the sclerotome. The muscle plate extends from the dorsal edge of the sclerotome to the dorso-median angle of the wall of the somite, and the dermatome from this point to the nephrotome. nSr Mj/. ..ft 'j^- ^^jst'-i=^-!^ l^cp. ^^^.: ~\ ^A. S26'. Sc/er -,£i-iv5'^ ^â j3;^v Coe/. 'A/ep/i. /;â .//. ;«g9^_, Fig. 108. â Transverse section through the twenty-sixth somite of a 29 s embryo. (Same embryo as Fig. 107.) Derm., Dermatome. My., Myotome. Scler., Sclerotome. V. c. p., Pos- terior cardinal vein. Other abbreviations as before. Fig. 109 is a section through the twentieth somite of the same embryo. The sclerotome is entirely mesenchymal, and its cells are extending between the notochord and aorta, and along the sides of the neural tube. The muscle-plate has now bent over so that its inner surface is being applied against the dermatome, but there is still a considerable cavity (myocoele) between the two, at the lateral angle of the dermo-myotomic plate. The lateral edge of the dermatome is freed from the nephrotome, and turns in to a slight extent. Other details are readily understood from the figure. The growth of the free edge of the muscle-plate towards the free lateral edge of the dermatome continues as illustrated in. 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 Lillie
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