CHAP, iv.] HEARING. 1377 



distribution and behaviour of similar structures in invertebrates. 

 We have further seen (618) that the vestibular nerve, the division 

 of the auditory nerve distributed to the maculae and cristae, differs 

 in its characters, in its mode of development and especially in its 

 central tracts and central endings from the cochlear nerve, the 

 division of the auditory nerve distributed exclusively to the organ 

 of Corti in the cochlea ; and it is stated that the vestibule may be 

 injured without any marked effect on hearing. But we are not 

 thereby justified in concluding, as some have done, that the 

 vestibular nerve does not in any way serve as the channel of 

 auditory impulses. In the first place, the evidence concerning the 

 ampullar afferent impulses, as ( 643) we called them, is by no 

 means complete ; it is still less complete as regards the utricle 

 and saccule. It is certainly not strong enough to justify the 

 conclusion that auditory impulses are not generated in the 

 vestibule, whatever else may happen there. In the second place, 

 vertebrates, lower in the scale than birds and reptiles, namely, 

 fishes, though they have a well-developed vestibular labyrinth, 

 possess either no cochlea at all or the merest trace of one, and 

 yet undoubtedly are the subject of auditory sensations, in some 

 cases of acute sensations. The evidence that fishes hear seems 

 irresistible, they are said to respond to musical sounds ; and yet 

 those who hold the views just explained are driven to maintain 

 either that fishes do not hear in the true sense of the word but 

 only feel vibrations, or that they hear by means of an insignificant 

 fragment of their relatively large vestibule. The structure of 

 the piscine and amphibian vestibular auditory epithelium is in 

 the main, putting aside smaller matters, such as the length of the 

 auditory hairs, the size and abundance of otoliths and otoconia 

 and the like, so identical with that of birds and reptiles and 

 of mammals, that it is impossible to resist the conclusion that 

 it serves the same purpose in all the several classes. In birds 

 and reptiles the short rudimentary nearly straight tubular cochlea 

 possesses a short basilar membrane, an auditory epithelium in 

 which a distinction of outer and inner hair-cells is foreshadowed, 

 and a tectorial membrane. But if we are to suppose that these 

 creatures receive auditory impulses exclusively from the cochlea, 

 and none at all from the vestibule, it is a matter of wonder that 

 the cochlea of the, for the most part, dumb crocodile should appeal- 

 almost as highly developed as that of the vocal bird. Or again, 

 if the bird and reptile already possessing a cochlea still derive 

 auditory sensations by means of the vestibule, we may conclude 

 that mammals also do the same. 



The whole evidence then goes to shew that even in man the 

 vestibule plays an important part in hearing. As we said above 

 the distinction between noise and music is a quantitative and 

 fluctuating one ; indeed the tendency of inquiry seems to shew 

 that the quality or timbre of a sound, and it is this which so 



