io68 



THE SENSES 



semicircular canals, the endolymph of which has, therefore, free com- 

 munication with that of the vestibule and cochlea. But although the 

 semicircular canals and vestibule belong anatomically to the internal 

 ear, and are supplied by branches of the auditory nerve, we have no 

 positive proof that in the higher animals, at least, they are in any way 

 concerned in hearing; and since experiment has assigned them a 

 definite function of another kind (p. 936), we shall not consider them 



str.v. 



Fig. 456. Longitudinal Section through the Cochlea of a Cat (Schafer, after Sobotta) 

 X 25 . dc, canal or duct of cochlea ; scv, scala vestibuli ; set , scala tympani ; w, bony 

 wall of cochlea; C, organ of Corti ; mR, Reissner's membrane ; n, fibres of cochlear 

 nerve; gsp, ganglion spirale; str.v., stria vascularis. 



further in this connection. The seala media contains the organ of Corti, 

 which (Fig. 458) consists of a series of modified epithelial cells planted 

 upon the basilar membrane. The epithelial cells are of three kinds: 

 (i) supporting epithelial cells; (2) the pillars or rods of Corti, in two 

 series (inner and outer), sloped against each other like the rafters of a 

 roof, and covering in a vault or tunnel which runs along the whole of 

 the scala media from the base to the apex of the cochlea; (3) the hair- 

 cells, around which the fibres of the auditory nerve arborize. These 

 last are columnar epithelial cells, surmounted by hairs. They are 



