652 



MEDULLA OBLONGATA AND THE CRANIAL NERVES 



peripheral receptor, and the other with the central nucleus. If we 

 now follow these fibers in the latter direction, we will find that they 

 pursue a separate course; those contained in the vestibular branch 

 ending in the nuclei of Deiters and Bechterew in the cerebellum, and 

 those belonging to the cochlear division in the ventral and dorsal 

 nuclei of the pons. From these primary relay stations the auditory 

 impulses are conveyed onward to the auditory center in the superior 

 gyrus of the temporal lobe of the cerebrum, but the course pursued 

 by them, has not been fully made out as yet. It seems, however, 

 that the largest number of the fibers arising in the ventral or accessory 

 nucleus acusticus, cross to the opposite side of the cerebrum. They 



TO VERMIS 



TO HEMISPHERE 



fiJ.b 



FIBRES OF 

 VESTIBULAR 

 ROOT 



NERVE 

 ENDINGS 

 IN MACUL>E 

 4.AMPULL/& 



Fig. 324. — The Course and Connections of the Fibers Forming the Vestibular 

 Root of the Auditory Nerve. 

 r., Restiform body; F, descending root of fifth nerve; p., principal nucleus of ves- 

 tibular root; d, fibers of descending vestibular root; n.d., a cell of the descending ves- 

 tibular nucleus; Z>, nucleus of Deiters; B, nucleus of Bechterew; n.t., nucleus tecti 

 (fastigii) of the cerebellum; pZ6., posterior (dorsal) longitudinal bundle. {Schafer.) 



select, however, somewhat different routes. -Some of them tend 

 directly across through the corpus trapezoideum, while others reach 

 this structure by passing around the restiform body and through the 

 tegmental region. From here they attain the superior olivary body 

 of the same and opposite sides and subsequently the lateral fillet or 

 lemniscus. Having traversed the colliculus or median geniculate 

 body, they terminate eventually in the psychic area for audition, 

 situated in the superior gyrus of the temporal lobe. . 



The dorsal nucleus or tuberculum acusticum is connected with 

 this center by secondary sensory neurons which form the medullary 

 or auditory striae, a band of fibers traceable along the floor of the 

 fourth ventricle. At the median raph^ these fibers turn and a large 



