28 IRVING HARDESTY 



cal turns, the outer sustentacular cells being higher and forming a 

 thicker ridge than in the basal end. Thus, measurement through 

 the middle of the outer hair cells will give an approximate aver- 

 age of the thickness in each case. The degree of the axial in- 

 cline of the surface of the organ decreases toward the basal end, 

 at which it is almost absent. Attention is further called to the 

 fact that in the basal end of the coil of the adult cochlea (f g. 4), 

 both the epithelium lining the internal spiral sulcus and that 

 known as the cells of Claudius are considerably thicker than 

 in the more apical regions. The axisward incline of the outer 

 rods of the organ increases slightly in passing from the basal 

 toward the apical end. This is not so evident in figures 1 to 4 

 as it was in other sections of adult cochleae. Gray ('00), in 

 suggesting a modification of the Helmholtz theory of hearing, 

 noted that the rods of the spiral organ and the hair cells became 

 smaller in passing from the apex to the base of the cochlea. 



The resonance theory, elaborated by Helmholtz, was based 

 upon erroneous anatomical descriptions of the basilar membrane 

 by others. Requiring that the membrane be composed of sepa- 

 rate fibers of varying length and free to exercise sympathetic 

 vibrations in response to sound waves of varying length imparted 

 to the endolymph, the theory must be abandoned. The basilar 

 membrane not only does not consist of independent fibers, 

 but it is blanketed on both its sides by thick continuous layers 

 of other tissue, the thickest of which is the cells of the spiral 

 organ itself. The telephone theory of hearing, suggested by 

 Rinne in 1865 and Voltolini in 1885, elaborated by Rutherford 

 in 1886 and further by Waller in 1891 and Meyer in 1898, was 

 likewise applied to the basilar membrane. Denying the pos- 

 sibilit}^ of the selective or sympathetic resonance required by 

 the Helmholtz theory, it -assumes that the vibrations producing 

 sound act upon the basilar membrane as a whole; that the 

 vibration frequencies induced in the tympanic membrane by 

 given sound waves are repeated by such extents of the basilar 

 membrane, beginning at the basal end, as the resistance offered 

 by the components of the apparatus and the inertia of the mem- 

 brane will allow. At one time in its development, the tele- 



