. The development of the chick : an introduction to embryology. Embryology; Chickens -- Embryos. FROM TWELVE TO THIRTY-SIX SOMITES 185 52, (see Keibel and Abraham, Normaltafeln). In an eight-day chick the number of somites is again about 42, including the four fused with the skull. Thus the ten somites formed last are again lost. This points towards a long-tailed ancestry for birds. ^'Although the somites have the same fundamental structure in all parts of the body, they differ greatly in many respects" (Williams). It is not, however, our purpose to consider the indi- vidual characters of
. The development of the chick : an introduction to embryology. Embryology; Chickens -- Embryos. FROM TWELVE TO THIRTY-SIX SOMITES 185 52, (see Keibel and Abraham, Normaltafeln). In an eight-day chick the number of somites is again about 42, including the four fused with the skull. Thus the ten somites formed last are again lost. This points towards a long-tailed ancestry for birds. ^'Although the somites have the same fundamental structure in all parts of the body, they differ greatly in many respects" (Williams). It is not, however, our purpose to consider the indi- vidual characters of each pair of somites, but rather the relations common to all. Each somite is composed of an epithelial wall of high, columnar cells, enclosing a core of cells that nearly fills the cavity (Figs. 112, 113, etc.). From each somite there arise three parts of fundamental significance, viz., the sclerotome, the muscle plate, and the cutis plate (dermatome), the primordium of the axial /).â¬/:. S ^^1 â ^^3t^ Coe/ ^^^?^^-*,. ^i? â Som'pL N'c/i. IVD. //epA ^; JiO- Coel. ^/'^y Fig. 107. â Transverse section through the last somite of a 29 s embryo. n. Cr., Neural crest. Neph., Nephrotome. W. D., Wolffian duct. Other abbreviations as before. skeleton, the voluntary muscles (excepting those of the head), and derma respectively. The manner of origin of these parts may be studied fully in an embryo of 25 to 30 somites, by com- paring the most posterior somites, in which the process is begin- ning, with somites of intermediate and anterior positions in the series, which show successively later stages. Figs. 107, 108, 109, and 110 represent transverse sections through the twenty-ninth, twenty-sixth, twentieth, and seven- teenth somites of a 29 s embryo. In the twenty-ninth somite. 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
Size: 2288px × 1092px
Photo credit: © Central Historic Books / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorlilliefrankrat, bookcentury1900, booksubjectembryology
