The Typical Form of the Cochlea and its Variations. 421 



correlation of cochlear sizes with gross bulk makes any such assumption 

 highly untenable. If this be granted, then it would seem that the absolute 

 length of the basilar membrane (and, therewith, the scale of dimensions of 

 the cochlea as a whole) is neither relatively, nor perhaps at all, important 

 for efficiency of hearing. It is rather the index of the basilar membrane that 

 counts, its length relatively to the size of the organ as a whole. This 

 conclusion is supported by the fact elucidated above (10) that the chief 

 internal variation of cochlear structure is the number of whorls or the 

 relative length of the basilar membrane. 



But if we thus abrogate the importance of the absolute length of the 

 basilar membrane, may we not also sacrifice the absolute breadth of it as 

 well, and within limits the absolute number of its transverse fibres ? These 

 limits seem inevitable, in so far as pitch discrimination could hardly be 

 refined much beyond the subdivision given by the transverse fibres ; but in 

 a larger organ it need not approach even within some distance of that sub- 

 division. I have elsewhere (op. cit.) tried to prove that the most important 

 property of the basilar membrane in its longitudinal aspect is its elasticity ; 

 and that a functional or psychical hearing, in all respects similar or parallel to 

 our own, in so far as its sensory integrations are concerned, might be got from 

 any absolute length of basilar membrane. The perfection of its efficiency 

 would depend only upon the elasticity of the membrane and its relative 

 length. The results of this paper bear well with this theory. On the other 

 hand, it must be noted that these results are not directly incompatible with 

 the hypotheses of any of the chief physiological theories of hearing. 



VOL. LXXX1X. — B. 



