. The development of the sympathetic nervous system in mammals. Development.—In embryos 10 mm. in length, the anlagenof the prevertebral plexuses may be recognized as small cell-aggregates lying along the ventro-lateral surfaces of the aorta inthe dorsal and the lumbar regions. In these regions the sympa-thetic trunks are not sharply limited ventrally. Cells becomeseparated from their ventral margins and migrate ventrally alongthe sides of the aorta (fig. 11, ). In the region of the 234 ALBEHT Kr:VTZ suprarenals, such cells have descended as far as the mesial sur-faces of these bodies w
. The development of the sympathetic nervous system in mammals. Development.—In embryos 10 mm. in length, the anlagenof the prevertebral plexuses may be recognized as small cell-aggregates lying along the ventro-lateral surfaces of the aorta inthe dorsal and the lumbar regions. In these regions the sympa-thetic trunks are not sharply limited ventrally. Cells becomeseparated from their ventral margins and migrate ventrally alongthe sides of the aorta (fig. 11, ). In the region of the 234 ALBEHT Kr:VTZ suprarenals, such cells have descended as far as the mesial sur-faces of these bodies which, at this time, appear as compact ceU-colunms m^ore or less circular in transverse section, hing parallelwith the aorta a short distance from its ventro-lateral surfaces(fig. 11, supr.). Posterior to the suprarenals, small cell-aggre-gates are present aU along the ventro-lateral surfaces of the aortaas far as the origin of the ihac arteries. It is impossible, in thisstage, to determine the limits of the anlagen of the several sath- ^**>••• cmp. Fig. 11. Transverse section through the sympathetic trunks and the supra-renal bodies of an embryo 9 mm. in length, X 150. pathetic plexuses in this region. The only distinction betweenthe ceU-aggregates which constitute the anlagen of the renal, the abdominal aortic, and the hj-pogastric plexusesconsists in a difference in degree of development. Developmentproceeds somewhat more rapidly in the anterior than in the pos-terior region. In transverse sections thiough this region, tracesof one or the other of these plexuses appear in nearly every sec-tion. SYMPATHETIC SYSTEM IN MAMMALS 235 In embryos 13 mm. in length, the cell-aggregates lying alongthe ventro-lateral surfaces of the aorta have become more pro-nounced. The greatest development occurs in the region of thesuprarenals. At a few points, fibers may be traced from thesympathetic trunks into the anlagen of the prevertebral plexuses(fig. 12, ). In the r
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectmammals, bookyear1910
