The Nature of the Tectorial Membrane 151 



of the stimuli in the perception mechanism. Lavdowsk}', Hensen, 

 Nuel and others describe the basilar membrane, in the spiral lamina, as 

 being composed of independent, radially disposed fibers. This and tlie 

 further observations that the basilar membrane is considerably wider 

 (and therefore its fibers longer) at the apex than in the basilar coils of 

 the cochlea, led Helmholtz to advance the theory of hearing which 

 bears his name. This theory involves the sympathetic vibration of the 

 different "fibers"' of the basilar membrane in resonance with the atmos- 

 pheric waves as transmitted to the endolymph by the tympanic mem- 

 brane and auditory ossicles, and it assumes that the vibrations of those 

 fibers involved by a given stimulus cause the hairs of the hair cells 

 overlying the fibers to rub upward against the tectorial membrane. It 

 thus assumes, further, that the cochlea has the power of analysis of 

 sound or that the perception of tone is mediated by different parts of the 

 cochlea. Ter Kuile, '00, in a purely theoretical paper dealing with the 

 transmission to the hair cells of energy from the supposedly vibratory 

 basilar membrane, shows that the hairs do not rub against the tectorial 

 membrane, but strike its under surface vertically. Ewald, '99 and '06, 

 accepts the idea of the basilar membrane and experiments with thin 

 rubber membranes placed under fluid, finding that vibrations may be 

 induced in them in response to atmospheric waves. In fact, with but 

 two exceptions that I know of, all of the investigators of physiological 

 acoustics since Helmholtz have accepted the assumption that the basilar 

 membrane is the vibratory mechanism, and in their writings have merely 

 put forth various modifications of the original conception. The two 

 exceptions are Kishi, '07, and Shambaugh, '07, both of whom assume that 

 the tectorial membrane is the vibratory mechanism, ]ioth claiming the 

 power of resonance in it, as will be mentioned below. 



As noted by Gray, '00, the explanations of hearing as now offered 

 may be divided into two general theories: (1) The Eesonance Theory, 

 suggested by the work of Hensen, ISTuel and others, propounded and 

 elaborated by Helmholtz and variously modified ever since in its appli- 

 cation to the cochlea ])y different investigators, and (3) The Telephone 

 Theory. 



The latter theory was suggested by Einne in 1865, supported by 

 Voltolini in 1885, more fully elaborated by Eutherford in 1886, modi- 

 fied by Waller in 1891, and further modified by Max Meyer in 1898. 

 It assumes that the transformed sound waves as imparted to the endo- 

 lymph affect the structures of the cochlea as a whole. 



