TONES BY INFLUENCE. 195 



with each harmonic, a smaller circle was produced. These 

 marked the nodal lines, which correspond to the harmonic 

 nodes of vibrating strings. Chladni applied these observa- 

 tions to the vibrations of round and square plates of glass 

 fixed at the centre, damped by the finger at various points, 

 and thrown into vibration by a violin-bow. In 1824, Savart 

 repeated many of the experiments of Chladni, and extended 

 them to the membrana tympani of the human subject, in 

 which he observed analogous phenomena, though they were 

 less distinct, on account of the small extent of the vibrating 

 surface. 1 Of course, the vibrations of the membrana tym- 

 pani must take place in accordance with physical laws ; but 

 how far these laws are applicable to the physiology of audi- 

 tion, is a question which we shall discuss fully in connection 

 with the functions of different portions of the auditory ap- 

 paratus. 



We have thus discussed various points in the physics of 

 sound, some of them with an elaborateness which might seem 

 out of place in a work on physiology. It must be remem- 

 bered, however, that the laws of acoustics are nearly all defi- 

 nitely settled ; that we have an absolutely-certain mathemat- 

 ical demonstration of the laws of musical vibrations ; and 

 that the ear recognizes these laws, and recognized them long 

 before they were ascertained by physical experimentation, for 

 certain sounds and combinations of sound simply give pleas- 

 ure, while others are disagreeable and discordant. It is suffi- 

 ciently evident that, if musical combinations be subjected to 

 certain inevitable laws, these laws form the only true basis of 

 the study of the mechanism of audition. It will be found, 

 indeed, that no point has been discussed in this chapter, that 

 is not essential to a clear comprehension of the physiology of 

 hearing. 



1 SAVART, Recherches sur les usages de la membrane du tympan et de Toreille 

 externe. Journal de physiologic, Paris, 1824, tome iv., p. 183, et seq. 



