204: SPECIAL SEXSE3. 



the muscles of the ear so as to put the tympanic membrane 

 in such a condition of tension as to respond to a given note 

 and to recognize the position of this note in the musical scale. 

 Finally, an accomplished musician, in conducting an orchestra, 

 can, by a voluntary effort, direct his attention to certain in- 

 struments, and hear their notes distinctly, separating them, 

 as it were, from the general mass of sound, can distinguish 

 the faintest discords, and immediately designate a single in- 

 strument making a false note. 



The fact that rapid successions of notes are readily appre- 

 ciated does not of necessity argue against the possibility of 

 following these notes with the muscles of the ear ; for the 

 muscles of the larynx may act so as to produce successions 

 of notes as rapidly as they can be correctly appreciated. Nor 

 does the fact that we must prepare the tympanic membrane 

 for certain notes militate against the theory we have just 

 given, for musical compositions present melodious successions 

 in a certain scale, the notes of which bear well-defined harmo- 

 nious relations to each other, and we immediately appreciate 

 a change in the key, which is simply a change in the funda- 

 mental. These changes in the key must be made in accord- 

 ance with the laws of modulation ; otherwise they are harsh 

 and grating. Modulation in music is simply a mode of pass- 

 ing from one key to another by certain transition-notes or 

 chords, which seem inevitably to lead to a certain key, and to 

 no other. Finally, the laws of vibration by influence show 

 that a single vibrating membrane returns the quality as well 

 as the pitch of tones and combinations of tones as well. 



The theory we have just given of the possible action of 

 the membrana tympani is an elaboration of the view ad- 

 vanced by Everard Home. 1 Unfortunately for the simplicity 

 of the mechanism of hearing and the idea of division and 



1 HOME, On the Organ of Hearing. Lectures on Comparative Anatomy, Lon- 

 don, 1823, vol. iii., p. 268, et seg. In this article, there was no experimental 

 proof given of the theory advanced, and it does not seem that the laws of vibra- 

 tion by influence were fully recognized. The author erred, also, in assuming that 

 the membrana tympani itself is a muscular membrane. It is probably for these 



