226 SPECIAL SENSES. 



auditory nerve which are essential to the sense of hearing 

 and which receive the impressions of sound are distributed 

 mainly in the cochlea. When we come to analyze sonorous im- 

 pressions, we find that they possess various attributes, such as 

 intensity, quality, and pitch, which have been discussed rather 

 fully under the head of the physics of sound. As far as 

 the terminal filaments of the auditory nerve are concerned, 

 it is evident that the intensity of sound is appreciated in pro- 

 portion to the power of the impression made upon these 

 nerves, and this point does not demand elaborate discussion. 

 With regard to quality of sound, we have seen that this is 

 due to the form of sonorous vibrations, and that most mu- 

 sical tones are compound, their quality depending largely 

 upon the relative power of the harmonics, partial tones, 

 etc. We have also seen that consonating bodies repeat 

 by influence, not only the actual pitch of tones, but their 

 quality. If there be in the cochlea an anatomical arrange- 

 ment of rods or fibres by which the sonorous vibrations, con- 

 veyed to the ear by the atmosphere, are repeated, there is 

 reason to believe that the quality, as well as the pitch, is re- 

 produced. Narrowing down the question, then, to its most 

 interesting and important point ; viz., the appreciation of dif- 

 ferences in the pitch of musical tones, we inquire whether 

 there be in the cochlea any arrangement by which the pitch 

 can be repeated. This inquiry can only be answered by a 

 study of the anatomical arrangement of the structures con- 

 nected with the terminal filaments of the nerves, and the ap- 

 plication of physical laws. 



The arrangement of the rods which enter into the struct- 

 ure of the organ of Corti has afforded a theoretical explana- 

 tion of the final mechanism of the appreciation of pitch. 

 Until we come to the internal ear, the action of different 

 portions of the auditory apparatus is simply to conduct and 

 repeat sonorous vibrations ; and the sole function of these 

 accessory parts, aside from the protection of the 'organs, is to 

 convey the vibrations to the terminal nervous filaments. 



