712 THE EAR 



brane. Beneath the overhanging vestibular lip of the limbus the mosaic 

 of large polygonal epithelial cells of the internal sulcus comes into 

 view. At the margin of the organ of Corti these are exchanged for the 

 broader cell ends of the inner sustentacular cells and the adjacent single 

 row of inner hair cells. 



The flattened rectangular head plates of the inner pillar cells form 

 the next row, the heads of the outer pillars projecting from beneath, 

 and extending beyond the heads of the inner pillar cells. These are fol- 

 lowed by the interdigitating phalanges of the cells of Deiters, which 

 enter into the formation of the reticular membrane, through the fenestra 

 of which the cilia of the three to five rows of outer hair cells project. 

 This cuticular membrane is continued outward, and beneath it are 

 successively seen the ends of the cells of Hensen, and of the cells of 

 Claudius. 



THE ACOUSTIC NERVE 



The acoustic nerve presents two distinct divisions both of which are 

 sensory, but which differ greatly as regards their central termination. 

 They likewise differ in their peripheral distribution. Within the inter- 

 nal acoustic meatus the nerve divides, each branch consisting of numer- 

 ous bundles. The vestibular (superior or anterior) division is supplied 

 with a ganglion of considerable size, the vestibular ganglion (of Scar pa) , 

 beyond which the nerve separates into three branches which supply, re- 

 spectively, the macula of the utricle, and the cristas of the superior and 

 lateral semicircular canals, in the neuro-epithelium of each of which 

 their terminal fibrils end in relation with the bases of the hair cells (Figs. 

 582 and 583). The remaining nerve fibers which are distributed to the 

 vestibule are derived from a branch of the cochlear (inferior or poste- 

 rior) division, and they supply in a similar manner the macula of the 

 saccule and the crista of the posterior semicircular canal. According to 

 Streeter (Amer. Jour. Anat., 190(5), the vestibular nerve contributes also 

 the innervation to the posterior canal and to the saccule, the cochlear 

 nerve supplying only the cochlea. 



The cochlear branch proper, cochlear nerve, enters the modiolus, 

 where it becomes abruptly narrowed by giving off numerous fine branches 

 which puss outward between the layers of the bony spiral lamina. Here 

 they form a continuous spiral succession of small nerve trunks, supplied 

 with many bipolar ganglion cells, which collectively form the spiral 

 ganglion (Fig. 58(5). They penetrate the margin of the bony sulcus 

 through the foramina nervosa, a succession of perforations, in the tym- 



