A NEW THEORY OF HEARING. 351 



of one part or another all locate the seat of stimulation by 

 high tones in the basal region and by low tones in the 

 apical. Pathological evidence, with the details of which 

 I am not acquainted, shows that injury — or at any rate 

 some injuries — to the apex of the cochlea lead to a 

 deafness to low tones, while the ear may still remain 

 sensitive to high ones. 



The objection seems at first sight to be fatal but, if I 

 have rightly understood what is the nature of the patho- 

 logical evidence, it is not so. 



A lesion of such kind as to destroy the elasticity of the 

 basilar membrane and thus prevent the passage of the 

 basilar wave to the apex of the spiral, would itself 

 provide a new passage for the wave direct from basilar to 

 Beissnerian at the injured spot, and the whole course of 

 the cochlear wave would thus be shortened, the injured 

 portion of the basilar serving as the turning-point of the 

 wave, serving in fact as a secondary helicotrema. Under 

 these circumstances waves of short period would still 

 "pass" within the cochlea though not at the normal 

 point, and the whole course being shortened, waves of 

 long period would now fail to pass in the cochlea and 

 deafness to low tones would be the consequence. 



In the earlier part of what has gone before, the attempt 

 to discover, by argument from physical considerations, 

 what changes of velocity of transmission the cochlear 

 wave undergoes in various parts of its length was abandoned 

 because the difficulties appeared insuperable. Having 

 now, however, seen the result of the physical consideration, 

 and being, as it seems, justified in concluding that the 

 stimulation of the nerve-ends is actually brought about by 

 the passing of waves on the two membranes, and the 

 resultant thrust of the tectorial membrane down upon the 

 sense-hairs we may use this physiological result as a means 



