FUNCTIONS OF THE INTERNAL EAR. 227 



Whatever be the functions of the membrana tympani in re- 

 peating sounds by influence, it is certain that this membrane 

 possesses no true auditory nerves, and that the auditory 

 nerves only are capable of receiving impressions 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. "With this 

 point clearly understood, we are prepared to study the prob- 

 able functions of the organ of Corti. 



When we consider the organ of Corti, with its eight thou- 

 sand or more rods of different lengths arranged with a certain 

 degree of regularity, a number more than sufficient to repre- 

 sent all the tones of the musical scale, we are not surprised 

 that eminent physiologists regard them as capable of repeat- 

 ing all the shades of tone heard in music. Helmholtz for- 

 mularizes this idea in the theory that tones conveyed to the 

 eochlea throw into vibration those elements of the organ of 

 Corti which are tuned, so to speak, in unison with them. 

 According to this hypothesis, the rods of Corti constitute a 

 harp of several thousand strings, played upon, as it were, by 

 the sonorous vibrations. 1 



It would be difficult to imagine any thing more beautiful 

 and simple than such an hypothesis as we have just quoted. 

 Attention and education enable persons endowed with what 

 is called a musical ear to discriminate between different tones 

 with great accuracy. Experiments have shown that the situ- 

 ation of the actual appreciation of tones may be restricted to 

 the cochlea ; and, in the cochlea, the only anatomical arrange- 

 ment, as far as we know, which points toward an apprecia- 

 tion of the pitch of different tones is that of the rods of 

 Corti. Still, it must be remembered that the cochlea is so 

 situated as to be removed from the possibility of experi- 

 mental investigation to prove the theory ; and we must care- 

 fully study the anatomical arrangement of the parts and the 



1 HELMHOLTZ, Theorie physiologiquc de la musiqiie, Paris, 1868, p. 183, et seq. 



