The anatomy of the nervous system, from the standpoint of development and function . yramids Pyramid, corticospinal tract Fie. 96. -? Fourth motor nucleus of vagus-? Nucleus of hypoglossal nerveTractus solitariusNucleus of spinal tract of N. VSpinal tract of trigeminal nerveFibers of hypoglossal >:?Reticular substanceDorsal accessory olivary nucleusMedia! lemniscusInferior olivary nucleusMedial accessory olivary nucleus— Pyramid, corticospinal trad Fig. 94-97.—Diagrammatic cross-sections to show the relation of the structures in themedulla oblongata to those in t
The anatomy of the nervous system, from the standpoint of development and function . yramids Pyramid, corticospinal tract Fie. 96. -? Fourth motor nucleus of vagus-? Nucleus of hypoglossal nerveTractus solitariusNucleus of spinal tract of N. VSpinal tract of trigeminal nerveFibers of hypoglossal >:?Reticular substanceDorsal accessory olivary nucleusMedia! lemniscusInferior olivary nucleusMedial accessory olivary nucleus— Pyramid, corticospinal trad Fig. 94-97.—Diagrammatic cross-sections to show the relation of the structures in themedulla oblongata to those in the spinal cord: Fig. 94, First cervical segment of spinal cord;Fig. 95, medulla oblongata, level of decussation of pyramids; Fig. 96, medulla oblongata, levelof decussation of medial lemniscus; Fig. 97, medulla oblongata, level of olive. At the level of the middle of the olive most of the fibers of the funiculus cune-atus and funiculus gracilis have terminated in their respective nuclei; and thenuclei also disappear a short distance farther rostrally (Fig. 97). With the. 136 THE NERVOUS SYSTEM disappearance of these fibers and nuclei there ceases to be any nervous sub-stance dorsal to the central canal, and this, which has been displaced dorsallyby the accumulation of the corticospinal fibers and those of the lemniscus ven-tral to it, opens out as the floor of the fourth ventricle (Fig. 97). The outline of the gray matter in the most caudal portions of the medullaoblongata closely resembles that of the spinal cord. The anterior columns arefirst cut off by the decussation of the pyramids (Fig. 95). Then the posteriorcolumns are displaced ventrolaterally due to the increased size of the posteriorfuniculi and the disappearance of the lateral corticospinal tracts from theirventral aspects. This rotation of the posterior column causes the apex ofthat column with its spinal tract and nucleus of the trigeminal nerve, which arecontinuous with the fasciculus dorsolateral and substan
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectnervoussystem, bookye
