196 THE HUMAN BODY. 



monic, and the note is thus decomposed by their sympathetic 

 vibration. The same phenomenon takes place in the in- 

 ternal ear. The fibres of Corti decompose the sounds, each 

 one vibrating in unison with the harmonic with which it 

 accords, arid these vibrations transmitted collectively to the 

 brain by the acoustic nerve give the sensation of the funda- 

 mental note, and of its timbre. But here, as in every other 

 instance, the living organ is infinitely superior to the machine 

 constructed by man. The fibres of Corti number upwards of 

 three thousand, and this gives four hundred sensitive cords 

 to each octave, of which the interval or space is one sixty- 

 sixth of a note. It is easy to understand from this how a 

 cultivated ear can appreciate the slightest difference in 

 sounds, as the eye perceives the least difference in the 

 degrees of light. 



This theory explains one of the most mysterious parts of 

 the mechanism of audition, it shows us the sonorous waves 

 exciting the Eolian harp of the acoustic nerve, just as direct 

 observation enables us to see the luminous image painted on 

 the retina. Just as a mirror and the camera obscura repre- 

 sent the eye, an instrument of music represents the ear; and 

 we follow the sonorous and the luminous waves to the point 

 where all is shrouded in mystery to sensation, to comprehend 

 which we must as little pretend, as to penetrate the mystery 

 of life, or of our own intelligence. 



But the ingenious explanation of M. Helmholtz does not 

 at first seem to make the phenomena of hearing as accessible 

 as those of seeing have become by means of optical instru- 

 ments. The convex mirror, and the productions of photo- 

 graphy, show us magnificent monuments and vast landscapes 

 reproduced in microscopic proportion; we have nothing like 

 this for the ear, and we are involuntarily led to contrast the 

 auditory organ and its fine canals with the grandeur of 

 sounds, and of the bodies from which they emanate. Phy- 

 sicists admit that the sonorous waves cross each other in the 

 air in nearly the same manner as in a fluid, without modify- 

 ing their curves, and it is thus that the distinctness of each 

 particular sound is perceived in an accord executed by 

 several different instruments; but, in order that this pheno- 



