906 NEUROLOGY 



Cochlear Nerve. The cochlear nerve or root, the nerve of hearing, arises from 

 bipolar cells in the spiral ganglion of the cochlea, situated near the inner edge of 

 the osseous spiral lamina. The peripheral fibers pass to the organ of Corti. The; 

 central ones pass down the modiolus and then through the foramina of the tractus 

 spiralis foraminosus or through the foramen centrale into the lateral or outer end 

 of the internal auditory meatus. The nerve passes along the internal auditory 

 meatus with the vestibular nerve and across the subarachnoid space, just above 

 the flocculus, almost directly medialward toward the inferior peduncle to terminate 

 in the cochlear nucleus. 



The cochlear nerve is placed lateral to the vestibular root. Its fibers end in two 

 nuclei: one, the accessory nucleus, lies immediately in front of the inferior peduncle; 

 the other, the tuberculum acusticum, somewhat lateral to it. 



The striae medullares (strice acusticce) are the axons of the cells of the tuberculum 

 acusticum. They pass over the inferior peduncle, and across the rhomboid fossa 

 to the median sulcus. Here they dip into the substance of the pons, to end around 

 the cells of the superior olivary nuclei of both sides. There are, however, other 

 fibers, and these are both direct and crossed, which pass into the lateral lemniscus. 

 The cells of the accessory nucleus give origin to fibers which run transversely in the 

 pons and constitute the trapezium. Of the trapezoid fibers some end around the 

 cells of the superior olivary nucleus or of the trapezoid nucleus of the same or 

 opposite side, while others, crossed or uncrossed, pass directly into the lateral 

 lemniscus. 



If the further connections of the cochlear nerve of one side, say the left, be con- 

 sidered, it is found that they lie lateral to the main sensory tract, the lemniscus, 

 and are therefore termed the lateral lemniscus. The fibers comprising the left 

 lateral lemniscus arise in the superior olivary and trapezoid nuclei of the same or 

 opposite side, while others are the uninterrupted fibers already alluded to, and these 

 are either crossed or uncrossed, the former being the axons of the cells of the right 

 accessory nucleus or of the cells of the right tuberculum acusticum, while the 

 latter are derived from the cells of the left nuclei. In the upper part of the lateral 

 lemniscus there is a collection of nerve cells, the nucleus of the lateral lemniscus, 

 around the cells of which some of the fibers arborize and from the cells of which 

 axons originate to continue upward the tract of the lateral lemniscus. The ultimate 

 ending of the left lateral lemniscus is partly in the opposite medial geniculate 

 body, and partly in the inferior colliculi. From the cells of these bodies new fibers 

 arise and ascend in the occipital part of the internal capsule to reach the posterior 

 three-fifths of the left superior temporal g}*rus and the transverse temporal gyri. 



Vestibular Nerve. The vestibular nerve or root, the nerve of equilibration, 

 arises from bipolar cells in the vestibular ganglion, ganglion of Scarpa, which is 

 situated in the upper part of the outer end of the internal auditory meatus. The 

 peripheral fibers divide into three branches: the superior branch passes through 

 the foramina in the area vestibularis superior and ends in the utricle and in the 

 ampullae of the superior and lateral semicircular ducts; the fibers of the inferior 

 branch traverse the foramina in the area vestibularis inferior and end in the saccule; 

 the posterior branch runs through the foramen singulare and supplies the ampulla 

 of the posterior semicircular duct. 



THE GLOSSOPHARYNGEAL NERVE (N. GLOSSOPHARYNGEUS ; NINTH 



NERVE) (Figs. 791, 792, 793). 



The glossopharyngeal nerve contains both motor and sensory fibers, and is dis- 

 tributed, as its name implies, to the tongue and pharynx. It is the nerve of ordinary 

 sensation to the mucous membrane of the pharynx, fauces, and palatine tonsil, and 

 the nerve of taste to the posterior part of the tongue. It is attached by three or 





