. Cunningham's Text-book of anatomy. Anatomy. DEVELOPMENT OF THE SYMPATHETIC SYSTEM. 681 trunks are homologous with the lateral and ventral branches of the somatic nerves in other regions. DEVELOPMENT OF THE SYMPATHETIC o,, ^ 2 ^Pi. i There are two diametrically opposite views of the mode of development of the sym- pathetic system. In birds and mammals the first rudiment of the sympathetic trunk occurs in the formation of a longitudinal unsegmented column of mesodermic cells (which stain more deeply than the mesoderm in which they lie) on either side of the aorta, and coterminous with
. Cunningham's Text-book of anatomy. Anatomy. DEVELOPMENT OF THE SYMPATHETIC SYSTEM. 681 trunks are homologous with the lateral and ventral branches of the somatic nerves in other regions. DEVELOPMENT OF THE SYMPATHETIC o,, ^ 2 ^Pi. i There are two diametrically opposite views of the mode of development of the sym- pathetic system. In birds and mammals the first rudiment of the sympathetic trunk occurs in the formation of a longitudinal unsegmented column of mesodermic cells (which stain more deeply than the mesoderm in which they lie) on either side of the aorta, and coterminous with it. This column of cells becomes joined at an early stage by the visceral branches of the spinal nerves which grow inwards from the main nerve trunks into the splanchnic area, and result from the division of the nerve into somatic and visceral parts. These visceral branches constitute the white rami communi- cantes. They receive contributions usually from both posterior and anterior roots, and gradually approaching the above-mentioned column of mesodermic cells, they become intimately associ- ated with the cells. In some cases fibres of the visceral nerves pass over the cellular column into the splanchnic area without connexion with it (Fig. 603). By the junction of these visceral nerves with the cells of the column, certain cells persist and produce the ganglia. The in- tervening portions of the column, by changes in the cells, and by the addition of fibres belonging to the visceral nerves, give rise to the com- missural cords. The cellular column, besides producing the gangliated trunk, by the further growth of its cells and their extension centrally and peripherally, produces the gray rami com- municantes, parts of the peripheral branches, and the peripheral (collateral and terminal) ganglia, as well as the medullary portion of the suprarenal gland. The cervical, lower lumbar, and sacral portions of the sympathetic gangliated trunk are secondary extensions from the primitiv
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1914
