USES OF THE PARTS CONTAINED IN THE COCHLEA. 763 



merits are lost after turning several times or violently shaking the head." 

 These observations of Flourens, at least as far as regards the influence of the 

 semicircular canals upon equilibration, have been confirmed by Goltz and 

 are sustained by observations upon the human subject in the condition 

 known as Meniere's disease. As far as can be judged from experimental 

 data, it does not seem probable that the nerves directly concerned in audition 

 are distributed to any considerable extent in the semicircular canals. In- 

 deed the uses of these parts is exceedingly obscure; for it can hardly be 

 admitted, upon purely anatomical grounds, that they are concerned in the 

 discrimination of the direction of sonorous vibrations, an idea which has been 

 advanced by some physiologists. 



Uses of the Parts contained in the Cochlea. There can be no doubt with 

 regard to the capital point in the physiology of the cochlea ; namely, that 

 those branches of the auditory nerve which are essential to the sense of hear- 

 ing and which receive the impressions of sound are distributed mainly in 

 the cochlea. An analysis of sonorous impressions shows that they possess 

 various attributes, such as intensity, quality and pitch. As far as the termi- 

 nal filaments of the auditory nerve are concerned, it is evident that the in- 

 tensity of sound is appreciated in proportion to the power of the impression 

 made upon these nerves. With regard to quality of sound, it has been seen 

 that this is due to the form of sonorous vibrations, and that musical sounds 

 usually are compound, their quality depending largely upon the relative power 

 of the harmonics, partial tones etc. It has also been 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 arrangement of rods or fibres by 

 which the sonorous vibrations conveyed to the ear by the atmosphere are 

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

 produced. 



The arrangement of the rods which enter into the structure of the organ 

 of Corti has afforded a theoretical explanation of the final mechanism of the 

 appreciation of pitch. With the exception of the internal ear, the action of 

 different portions of the auditory apparatus is simply to conduct and repeat 

 sonorous vibrations ; and the sole use of these accessory parts, aside from the 

 protection of the organs, is to convey the vibrations to the terminal, nervous 

 filaments. Whatever be the uses of the membrana tympani in repeating 

 sounds by influence, it is certain that this membrane possesses no true, audi- 

 tory nerves, and that the auditory nerves only are capable of receiving im- 

 pressions of sound. Thus hearing, and even the appreciation of pitch, is 

 not necessarily lost after destruction of the membrana tympani ; and if 

 sonorous vibrations reach the auditory nerves, they will be appreciated and 

 appreciated correctly. 



In view of the arrangement of the organ of Corti, with its eleven thousand 

 or more rods of different lengths arranged with a certain degree of regularity, 

 a number more than sufficient to represent all the notes of the musical scale, 

 it is not surprising that they should be regarded as capable of repeating all 

 the notes heard in music. Helmholtz formulated this idea in the theory that 



