. Anatomy, descriptive and applied. Anatomy. 828 THE NERVE SYSTEM the cord. The metamorphosis of the neuroepithelial columnar cells has been described (p. 806). The lateral walls thicken considerably, the central slit-like canal widens as the walls bulge out- ward in an angular manner, and the central tubular gray becomes a fluted column with dorsal and ventral ridges (or horns) enveloped by a rapidly growing mantle of axone bundles which become myelinic in successive stages. The bulging of the thickening walls in the dorsal and ventral as well as lateral directions produces the ventral fissur
. Anatomy, descriptive and applied. Anatomy. 828 THE NERVE SYSTEM the cord. The metamorphosis of the neuroepithelial columnar cells has been described (p. 806). The lateral walls thicken considerably, the central slit-like canal widens as the walls bulge out- ward in an angular manner, and the central tubular gray becomes a fluted column with dorsal and ventral ridges (or horns) enveloped by a rapidly growing mantle of axone bundles which become myelinic in successive stages. The bulging of the thickening walls in the dorsal and ventral as well as lateral directions produces the ventral fissure and the postseptum. The segmental nature of the spinal cord has been alluded to before with regard to the seg- mental derivation of the cerebrospinal ganglia and the disposition of the outgrowing nerve. Ventral aspect. Dorsal aspect. Fig. 605.—Distribution of cutaneous nerves. btmdles. There is a further mode of division into longitudinal systems based upon functional relationships. Two main categories of acti\'ity characterize the mechanism of the nerve system and find somatic expression in its architectural plan: First, actions in relation to the external world (somatic—involving skin, muscle, skeleton, etc.); second, internal activities concerned with the processes of nutrition and reproduction (visceral—involving the alimentary tract, vas- cular [blood and lymph], excretory, and reproductive systems). In each there is a twofold activity on the part of the nerve system: reception of stimuli and motor responses. In the cord (and to some extent in the brain as well) the following functional divisions may be distinguished and located anatomically (Fig. 602): Somatic sensor elements. Somatic motor elements. Visceral sensor elements. Visceral motor 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 wo
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1913
