The anatomy of the nervous system, from the standpoint of development and function . of spinal trad X. V Central canal Fig. 130.—Sensory nuclei projected upon a median sagittal section of the human brain lines, general somatic sensory nuclei; cross-hatching, visceral sensory nucleus; stipple,special somatic sensory nuclei. and mesencephalon (Fig. 132). It is composed in large part of long fibers whichreach the thalamus. The dorsal secondary afferent path of the trigeminal nerveconsists chiefly of uncrossed fibers and lies not far from the floor of the fourthventricle and the ce
The anatomy of the nervous system, from the standpoint of development and function . of spinal trad X. V Central canal Fig. 130.—Sensory nuclei projected upon a median sagittal section of the human brain lines, general somatic sensory nuclei; cross-hatching, visceral sensory nucleus; stipple,special somatic sensory nuclei. and mesencephalon (Fig. 132). It is composed in large part of long fibers whichreach the thalamus. The dorsal secondary afferent path of the trigeminal nerveconsists chiefly of uncrossed fibers and lies not far from the floor of the fourthventricle and the central gray matter of the cerebral aqueduct. It consist- inconsiderable part of short fibers (Cajal, 1911; Wallenberg, 1905; Economo,1911; Dejerine, 1914). The proprioceptive nuclei of the cranial nerves are not well known. Theyhave to do with afferent impulses arising in the muscles of mastication and in 184 THE NERVOUS SYSTEM the extrinsic muscles of the eye. Johnston (1909) has shown that the largeunipolar cells of the mesencephalic nucleus of the fifth nerve which give rise. Fig. 131.—Diagram of the nuclei and central connections of the trigeminal nerve: A, Semi-lunar ganglion; B, mesencephalic nucleus, N. Y.; C, motor nucleus, N. Y.; D, motor nucleus, ; E, motor nucleus, N. XII; F, nucleus of the spinal tract of N. V.; G, sensory fibers of the sec-ond order of the trigeminal path: a, ascending and b, descending branches of the sensory fibers,N. V.; c, ophthalmic nerve; d, maxillary nerve; e, mandibular nerve. (Cajal.) to the fibers of the mesencephalic root of that nerve, are probably sensory infunction. Willems (1911) and Allen (1919) believe that these are sensory fibers THE CRANIAL NERVES AND NUCLEI 185 to the muscles of mastication. If this interpretation is correct we are pre-sented with an exception to the rule that the afferent fibers of the cerebrospinalnerves take origin from cells located outside the cerebrospinal axis. This nu< leus lies in th
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