CHAP, iv.] HEARING. 209 



The cell substance, very delicate in nature, contains a number of 

 granules, and bears near the base a large, conspicuous, spheroidal 

 nucleus. From the free surface there projects a bundle of long 

 stiff hairs, the auditory hairs, which often stick together in the 

 form of an attenuated cone. Cells of this kind may be called 

 hair-cells, or for reasons which we shall see directly, cylinder cells. 

 The other kind of cell (Fig. 178 B 3, 4, 5) possesses a nucleus 

 smaller than that of the cylinder cell and having the form of a 

 short ellipsoid, placed vertically ; around this nucleus lies a 

 relatively small quantity of cell substance, delicate like that of 

 the cylinder cells but probably of a different nature. This scanty 

 cell body is prolonged upwards between the cylinder cells as a 

 rod-shaped process terminating abruptly at the surface, and 

 stretches in the opposite direction as a process which, frequently 

 but not always branched and irregular, reaches to and ends at the 

 surface of the dermis. These rod cells or spindle cells are much 

 more numerous than the cylinder cells, and their nuclei are 

 placed at different levels, some close upon the dermis, others at 

 different distances from it up to the level of the bases of the 

 cylinder cells. The nuclei of these rod cells thus occupy the 

 space between the bases of the cylinder cells and the dermis ; 

 they form in fact the nuclear layer spoken of above. It should 

 be added that the nuclei which form a row immediately above the 

 dermis are regarded by some authors as belonging to cells differing 

 from the rod cells, their cell substance being said to be confined to 

 the neighbourhood of the nucleus, and not to extend to the surface 

 of the epithelium ; these are spoken of as basal cells. 



According to the view which we are relating, a nerve fibre 

 of the auditory nerve after traversing the auditory cushion (Fig. 

 178 A) passes into the epithelium and losing both neurilemma 

 and medulla, though sometimes retaining the latter for a short 

 distance, makes its way as a naked axis cylinder between the rod 

 cells, taking sometimes a vertical, but often a more horizontal 

 direction. In its course it gives off fine lateral irregular branches, 

 (Fig. 178 B 2) often divides, is frequently very distinctly fibril- 

 lated, and eventually ends in a nest or brush of fibrillse, into 

 which the conical base of a cylinder cell fits, or with which the 

 -cell substance of the cell is continuous ; though appearances 

 support this latter view, it cannot be regarded as certain. The 

 nerve fibres appear to make no connections with the rod cells, 

 which are hence regarded as of the nature of supporting or sub- 

 sidiary structures ; the cylinder cells alone, and according to this 

 view it is these which bear the auditory hairs, are to be looked 

 upon as the functional terminal organs of the fibres of the auditory 

 nerve. 



Other observers, on the other hand, maintain that the auditory 

 hairs are borne not by the cylindrical cells but by the rod cells 

 {hence it is perhaps better to call the former cylinder cells rather 



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