568 THE NERVOUS SYSTEM. 



degree ; and it is supposed that certain insects may be capable of per- 

 ceiving sounds of very high pitch which are inaudible to the human 

 ear. To an organ of such acute sensibility a very low note, on the 

 other hand, would appear as a succession of distinct impulses. 



The limits of frequency, within which sonorous vibrations are per- 

 ceptible to man as musical sounds, are 16 double vibrations per second 

 for the lowest notes, and 38,000 for the highest. But, according to 

 Wundt, the exact discrimination of musical pitch is confined within 

 much narrower limits, especially for the higher notes. 



Duration of a Sound required for Sonorous Impressions. This 

 point has been investigated by Savart* in the following manner: He 

 ascertained, by experiment, that the ear could appreciate the pitch of a 

 sound made by a toothed wheel revolving at the rate of 10,000 shocks 

 per second. By successively removing the teeth from different portions 

 of its circumference, he diminished in a corresponding degree the time 

 during which the shocks were produced ; and he found that such a wheel 

 would give a sound of definite pitch with only two teeth adjacent 

 remaining. The double shock thus produced would occupy only -o^u- 

 of a second ; and this duration of impulses was sufficient to make upon 

 the ear a distinct musical impression. 



* Daguin, Traite Elementaire de Physique. Paris, 1869, tome i., p. 517. 



