332 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



would diminish and its inertia decreasing the expenditure 

 of like energy upon it would give it a greater velocity and 

 therefore a greater displacement — an effect comparable 

 with the " bore " in the Severn and similar rivers. 



The basilar, however, is not uniform in breadth : it is 

 about twelve times as broad in the apical region as in the 

 basal : that is the wave in passing forwards towards the 

 apex comes into successively narrower and narrower 

 portions of the canal and acts upon successively broader 

 and broader areas of the basilar membrane. The effect 

 of this is to exaggerate the effect of the narrowing canal 

 already described. In order that the same amount of 

 energy may be stored in potential form — to speak figura- 

 tively — in two fibres which are otherwise alike but of 

 different lengths the transverse displacement of the longer 

 one must be much greater than that of the shorter one. 

 The wave in passing forwards towards the apex will thus 

 rapidly gain in amplitude — and the importance of this 

 fact from a physiological point of view will be seen later. 



What changes in velocity result from this change in 

 width of the channels and in breadth of the membrane 

 as the wave passes on it is less easy to say. The two 

 influences — narrowing of canal and consequent decrease of 

 mass per unit length to be moved, and broadening of 

 membrane and consequent diminution of elastic pressure 

 per unit displacement — appear to counteract each other, 

 but whether the two effects balance each other or one 

 over-balances the other is a question which I have as yet 

 only guessed at on physiological and not on physical 

 grounds. The guess which will be justified later is that 

 the velocity of the wave and consequently its length (in 

 space, not in time) will be augmented. 



As to the absolute velocity at any part of its course — • 

 as distinct from its relative velocities in different parts of 



