ACTION OF THE TECTORIAL MEMBRANE 513 



frequency of the wave energy transferred to the surrounding 

 fluid. In the waves of less amplitude and higher frequencies, 

 vibrations must be reached which are unable to agitate the lam- 

 ina at all but may agitate the tectorial membrane alone, and 

 then those which agitate decreasing extents of this and with 

 decreasing excursion or amplitudes of vibration up to the func- 

 tional upper limit of the auditory apparatus. 



CONCLUSIONS 



Discussion of most of the usually described physiological 

 phenomena of hearing is not undertaken in this paper. It is 

 felt that the model, as compared with the actual auditory appara- 

 atus, is so crudely constructed and so gross in size that attempts, 

 based upon its behavior, to explain many of the seemingly 

 complex phenomena would be not only difficult but unprofitable 

 at the present stage of the study. The discussion is confined to 

 the more evident and more probably trustworthy suggestions 

 offered by the behavior of the model : 



(1) That the tectorial membrane is a vibratory structure and 

 from its consistency, shape, proportions and position, is the chief 

 vibratory structure in the cochlea. 



(2) That it may vibrate in such a way that a modification of 

 the telephone theory of hearing may be applied to it. 



(3) That sound waves of low vibration frequency produce 

 vibrations in the entire tectorial membrane regardless of ampli- 

 tude while those of higher frequency produce vibrations in vary- 

 ing extents of it, depending upon their amplitude. 



(4) That among the sound waves of the higher vibration 

 frequencies capable of being appreciated, the extent or length 

 of the tectorial membrane in which efficient vibrations may be 

 induced depends more upon the vibration frequency or pitch 

 than upon the amplitude of the sound waves. The higher fre- 

 quencies being damped out more readily than the lower, varying 

 extents of the membrane are affected according to the vibration 

 frequencies of the waves applied, the highest frequencies affecting 

 the thin, basal end of the membrane alone. 



(5) Some evidences of what may be considered resonance in 

 the tectorial membrane were indicated but were thought question- 



