344 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



length of the organ of Corti where a stimulation is 

 produced by a tone due to 100 vibrations per second. 

 Similarly let a stand for the uppermost point of passing 

 of waves produced by a tone of a vibrations per second. 



A tone a will thus produce cochlear waves passing at 

 points a, \ a, \ a, J a, etc. "Within prescribed limits stimu- 

 lation occurs at the point a only : at J a the amplitude 

 of displacement is too small to produce stimulation. 



A tone J a of equal intensity is, however, sufficient to 

 produce a stimulation at the point \ a : therefore if the 

 intensity of the tone a be so far increased as to produce a 

 cochlear wave of more than double its previous amplitude 

 (which means manifold more than double intensity), it also 

 will be able to stimulate the organ of Corti at the point 

 ^ a, but in the first instance the sensation due to the 

 stimulation at a will have been so enormously intensified 

 as to overpower this stimulation at J a, and the weak 

 second tone \ a will be heard either very faintly or not 

 at all. 



I have found by experiment, however, that if a tone a 

 be sounded loudly for five or ten minutes and then 

 increased gradually in intensity, the note J a, an octave 

 lower gradually becomes audible. It is therefore possible, 

 by gradually deafening oneself to a tone and then increasing 

 its intensity, to produce a sensation of a tone an octave 

 lower. 



The result arrived at in considering this third problem 

 is thus as follows : — 



A continuous constant tone within moderate limits of 

 intensity will produce stimulation of one region of the organ 

 of Corti and of one only : and increase of intensity beyond 

 these limits produces a stimulation of a region correspond- 

 ing to a tone an octave lower ; but this second stimulation 

 is so feeble as to be difficult or impossible of recognition, 



