Diseases of the nervous system .. . il these fibers of the nuclei ofthe posterior column enter the lemniscusthey are called fihro arcuatcp interna(Figs. 85, 91, 92). Thus we find a secondsensory crossing above the pyramidal de-cussation. All sensory fibers of the secondneurons, like the motor, find their way tothe brain by crossing over. Those whichpass from the lateral columns of the spinalcord into the lemniscus without cross-ing have passed through the anteriorcommissvre of the spinal cord from the posterior horn of the other side, whilethe fibras arcuata^ internae cause the crossing of the
Diseases of the nervous system .. . il these fibers of the nuclei ofthe posterior column enter the lemniscusthey are called fihro arcuatcp interna(Figs. 85, 91, 92). Thus we find a secondsensory crossing above the pyramidal de-cussation. All sensory fibers of the secondneurons, like the motor, find their way tothe brain by crossing over. Those whichpass from the lateral columns of the spinalcord into the lemniscus without cross-ing have passed through the anteriorcommissvre of the spinal cord from the posterior horn of the other side, whilethe fibras arcuata^ internae cause the crossing of the sensory tract from the pos-terior columns which until then had not been made. Hence the second sensoryneuron of the posterior roots of the spinal cord ascends to the medulla oblongatain the lemniscus on both sides of the raphe. We must trace this through thepons and the middle brain. The fibers of the second sensory neuron of the cranial nerves now unite,and, the lowest, the nucleus of the pneumogastric nerve (Fig. 87) whose cells. Fig. So.—Diagram of the CorRSE of theSensory Tracts from the PosteriorRoots to the Medulla. (After Edin-ger.) 90 HISTOLOGY OF THE CEXTRAL NERVOUS SYSTEM form the second neuron, sends its fibers through the raphe to the most dorsalregion of the crossed lemniscus. The same is true of the nucleus of the glosso-pharyngeal nerve. (Probably the ascending roots of the glosso-pharyngealand vagus send crossed fibers into the lemniscus tract; no positive knowledgeconcerning this is at hand.) The relations of the auditori/ nerve are more complicated. ^ These ariseat the height of the pons in the median portion of which, above the pyramidal Radix anterior Central motor path of conductionMotor nerve cell Sensory collaterals (reflex collateralPeripheral moti Peripheral motor ^^|nerve terminal Peripheral sensory nervfiber Peripheral sen sory nerve terminal
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