The Xature of the Tectorial Membrane 159 



the sensation experienced depends only upon the quality and intensity 

 of stimulus applied to the peripheral nerve endings. The specialization 

 of sensation is doubtless with reference to general groups only, and this 

 specialization dependent upon the locality of the cerebrum to which the 

 impulses aroused by external stimuli are borne. The optic nerve, stimu- 

 lated by touch (pressure) conveys impulses which are interpreted as sen- 

 sations of light; the acoustic nerve, stimulated by touch (tumors, etc.) 

 gives rise to sensations of sound. And it is very probable that within tlie 

 general groups, most manifest in touch, identical nerve terminations 

 acted upon by external stimuli varying in quality, give rise to sensations 

 varying according to the quality of the stimuli. 



It is considered neither possible nor necessary in this paper to consider 

 fully the numerous modifications and additions to the resonance theory. 

 Many of the papers are merely attempts to explain away the physiological 

 (and psychological) difiiculties and anatomical objections to the theory 

 as applied to the basilar membrane and the action of the organ of Corti. 

 It seems to the author that these objections, taken collective^, are such 

 that neither the resonance theory nor the telephone theory as applied to 

 the basilar membrane are any longer tenable. 



The fact has been frequently noted, and especially by ter Kuile, that 

 the tectorial membrane, in all species, is always entirely coextensive 

 with the organ of Corti, and is always sufficiently wide to cover the hair 

 cells, whether these are in linear series on either side of the rods, as in 

 mammals, or whether they are scattered throughout the entire epithelium 

 of the organ of Corti, as in birds and reptiles. Since the same cannot be 

 said of the basilar membrane, it seems very probable that the tectorial 

 membrane is more essential to the sense of hearing. Further, because 

 of its shape, its more logical position, above the auditory hairs, and its 

 far more delicate sensitiveness, the tectorial membrane seems much 

 better qualified to serve as the vibrating mechanism than the basilar 

 membrane. 



Siebenmann, '00, seems to have been the first to suggest that the 

 tectorial membrane is the structure agitated by sound waves, though the 

 inference drawn by Ayers, '91, amounted to something similar. Quite 

 recently Kishi and Shambaugh, realizing the anatomical disqualifications 

 of the basilar membrane, have attributed the power of resonance to the 

 tectorial membrane. 



Kishi, '07, after citing four anatomical objections, concludes that the 

 basilar membrane is not qualified for the vibrating mechanism of either 



