CHAP, iv.] HEAEING. 219 



lying to the outside of the ring encircling the head of its twin cell 

 of Corti ; it may be called the ' phalangar process.' Downwards 

 the body is prolonged, slanting outwards, as a cylindrical process 

 reaching as far as and becoming attached to the basilar membrane. 

 This part of the cell bears a rounded nucleus (n 1 ), and is, in the 

 greater part of its extent, of a delicate nature and easily destroyed ; 

 but on its inside, looking towards the rod of Corti, the-H6ell- 

 substance is differentiated into a cuticular band or thread (Jil), 

 which below is cemented. to the basilar membrane, and above may 

 be traced into the upward phalangar process and so to the 

 reticulate membrane. There seems good reason for regarding 

 this cell of Deiters as a structure analogous to the rod cells of 

 the crista and macula, but a structure more specially modified 

 than are they. We may probably consider it, like them, to 

 be essentially supporting or at least subsidiary in function, that 

 is to say, not in itself giving rise to auditory nervous impulses 

 but in some subsidiary way assisting the hair-cell proper, that 

 is the cell of Corti, to do so. It will be observed that the 

 cell of Deiters serves as a brace or tie between the reticulate 

 membrane above and the basilar membrane below, while at the 

 same time it is in such complete apposition to if not in continuity 

 with the cell of Corti, that we may justly suppose molecular 

 processes started in it to be readily communicated to that. 



The first row of outer hair-cells is placed at some little distance 

 from the outer rod of Corti, being separated from it by a space 

 corresponding to the length of the phalangar process of the rod- 

 head ; but the succeeding rows follow close on each other, and the 

 series is closed on the outside towards the spiral ligament by the 

 group of Hensen's cells. The phalangar process of the inner rod 

 is inclined somewhat upwards, and the same inclination is main- 

 tained by the reticulate membrane and the whole row of outer 

 hair-cells, there being a gradual ascent from the inner hair-cells to 

 the cells of Hensen. 



836. The cochlear nerve reaches the organ of Corti through 

 the spiral lamina. The centre of the base of the cochlea round 

 which the first whorl winds is scooped out into a hollow, and from 

 this a central canal, gradually narrowing, runs up the axis of the 

 whorls. The cochlear nerve lies in the hollow and is continued up 

 into the central canal ; in its course it gives off from the hollow 

 and from the central canal a series of bundles of nerve fibres which 

 pass radially into the spiral lamina, being like it arranged in a 

 spiral. At the bottom the nerve is thick ; it diminishes in bulk 

 as each bundle is given off, and ends by giving off its last bundle 

 near the top of the spiral. 



On their way through the spiral lamina in a radiate direction 

 all the bundles become connected with a collection of nerve cells, 

 arranged in a spiral band, the ganglion spirale, lying in the spiral 

 lamina (Fig. 177 Gfg.sp.). The cells of this ganglion closely 



