190 THE NERVOUS SYSTEM 



Many of the ascending branches of the vestibular nerve, after giving off 

 collaterals to the nuclei of Deiters and Bechterew, are prolonged in the tractus 

 vestibulocerebellaris, to end in the cortex of the cerebellum (Cajal, 1909). These 

 are joined by fibers arising in the superior and lateral vestibular nuclei which 

 also run to the cerebellum (Fig. 136). From the standpoint of its embryologic 

 development the cerebellum may properly be regarded as a highly specialized 

 vestibular nucleus (p. 196). 



Secondary Vestibular Paths. In addition to the fibers to the cerebellum 

 mentioned in the preceding paragraph two important tracts of fibers take origin 

 in the superior and lateral vestibular nuclei. One of these was encountered in 

 the study of the medial longitudinal bundle. Cells in the superior and lateral 

 vestibular nuclei give rise to fibers which run to the medial longitudinal fascicle 

 of the same and of the opposite side, and through it reach the motor nuclei of the 

 ocular muscles (Fig. 136). In this way there is established an arc, which makes 

 possible the reflex response of the eye muscles to afferent impulses arising in the 

 vestibule and semicircular canals of the ear. The other bundle was considered 

 in connection with the spinal cord as the vestibule spinal tract, the fibers of 

 which take origin from the cells of the lateral nucleus and descend into the 

 anterior funiculus of the same side of the cord. These fibers serve to place the 

 primary motor neurons of the spinal cord under the reflex control of the vestib- 

 ular apparatus. 



From the medial border of the principal vestibular nucleus many scattered 

 fibers cross the raphe and enter the reticular formation of the opposite side, where 

 they become longitudinal fibers. No tract to the thalamus is known, a fact 

 which is in keeping with this other, that ordinarily the activities of the vestib- 

 ular apparatus are not clearly represented in consciousness. 



SUMMARY OF THE ORIGIN, COMPOSITION, AND CONNECTIONS OF THE CRANIAL 



NERVES 



The olfactory and optic nerves and the nervus terminalis, which have not 

 yet been considered in detail, have been included in this summary for the sake 

 of completeness. 



The nervus terminalis is a recently discovered nerve which arises from the 

 cerebral hemisphere in the region of the medial olfactory tract or stria. It is 

 closely associated with the olfactory nerve and its fibers run to the nasal septum. 

 The origin, termination, and function of its component fibers are not yet under- 

 stood (McKibben, 1911; Huber and Guild, 1913; McCotter, 1913; Johnston, 



