SPECIAL SENSES. 



cession, produced by the voice, trumpet, violin, clarinet, or 

 other musical instruments, it can be easily noted that the 

 quality of the tone, as well as the pitch, is rendered by a re- 

 sounding string ; and the same is true of combinations of 

 tones. 



The above laws of tones by influence have been illustrated 

 by strings merely for the sake of simplicity ; but they have 

 a more or less perfect application to all bodies capable of pro- 

 ducing musical tones, except that some are thrown into vibra- 

 tion with more difficulty than others. An interesting appli- 

 cation of these laws, however, particularly with reference to 

 the physiology of the ear, is in the case of stretched mem- 

 branes ; for this brings to our mind the possible action of the 

 membrana tympani. 



If we have a thin membrane, like a piece of bladder or 

 thin rubber, stretched over a circular orifice, such as the 

 mouth of a wide bottle, this can be tuned to a certain note. 

 "When arranged in this way, the membrane can be made to 

 sound its fundamental note by influence. In addition, the 

 membrane, like a string, will divide itself so as to sound the 

 harmonics of the fundamental, and will likewise be thrown 

 into vibration by the 5th, 3d, etc., of its fundamental tone, 

 thus obeying the laws of vibrations of strings, though the 

 harmonic sounds are produced with greater difficulty. 



At about the beginning of this century, Chladni demon- 

 strated the spontaneous division of vibrating plates and mem- 

 branes by a very simple experiment. 1 lie covered the surface 

 with a delicate, uniform layer of fine sand. Arranged in this 

 way, it is evident that the sand would be thrown off from 

 the vibrating portions and collected upon those portions which 

 remained comparatively quiescent, provided that the surface 

 became divided into different areas of vibration. This was 

 ascertained to be the fact. "When the fundamental tone was 

 sounded, the entire plate was thrown into vibration, and the 

 sand was collected in a circular line near its periphery ; and, 



1 CHLADXI, Die Akustik, Leipzig, 1802, S. xvi., 78, et seq., and S. 118, et seq. 



