SENSE AREAS AND ASSOCIATION AREAS. 



201 



gators vary considerably. The eighth cranial nerve springs from the 

 bulb by two roots: the external and the internal. The former has 

 been shown to supply, mainly at least, the cochlear portion of the 

 internal ear, and is, therefore, the auditory nerve proper. This 

 division is spoken of as the cochlear branch. The internal root sup- 

 plies mainly the vestibular branch of the internal ear, and is there- 

 fore spoken of as the vestibular branch (see Fig. 88) . It seems cer- 

 tain that the latter is not an auditory nerve, but is concerned 



Posterior nucleus. 



Deiters's nucleus. 



Dorsal nucleus. 

 Ventral nucleus. 



Cochlear branch. 



Vestibular branch. 



Semicircular 

 canals. 



Scarpa's ganglion. 

 Cochlea. 



Spiral ganglion. 

 Fig. 88. The medullary nuclei of the eighth nerve. (From Poirier and Charpy.) 



with peculiar sensations from the semicircular canals and vestibule 

 that have an important influence on muscular activity, especially 

 in complex movements. The central course of these two roots is 

 quite as distinct as their peripheral distribution, a fact that bears 

 out the supposition that they mediate different functions. The 

 vestibular branch ends in the nucleus of Deiters, the nucleus of 

 Bechterew, and the nucleus fastigii of the cerebellum. Through 

 these nuclei reflex connections are made with the motor centers 

 of the cord and midbrain, and probably also with the cerebellum. 

 The path is not known to be continued forward to the cerebrum. 

 The central course of the cochlear branch is indicated schematically 



