THE EAR OF MAN. 22$ 



a ce sujet ne reposent pas sur des bases suffisantes 

 pour que nous y arretions ici." 



Audition is the resultant of all the wave motions, 

 transformed and transmitted to the auditory centre in 

 the brain by the fibres of the auditory nerve. 



There are several kinds or conditions of auditory 

 stimuli, depending, first, on the intensity or force of 

 sound {i.e. the amplitude of vibration) ; second, on the 

 pitch of sound {i.e. the number of vibrations in a given 

 unit of time); and third, the quality or timbre {i.e. the 

 result of the form of the sound wave). Upon the com- 

 bination of these conditions, in varying proportions as 

 they occur, depend the character of the auditory im- 

 pressions. 



The variability in the powers of auditory perception 

 among animals is much greater than is commonly sup- 

 posed. As instances of increased sensitiveness above 

 that of the human ear one may mention mice, cats, 

 and other nocturnal animals. Galton found that the 

 house cat among domestic animals possessed a wonder- 

 ful capacity to perceive shrill tones, and it is a common 

 experience that the cat's ear is super-sensitive to audi- 

 tory stimuli. 



All vertebrates above the fishes are provided, like 

 man, with a tympanic membrane and a chain of bones, 

 or its functional equivalent, which serve to transmit 

 vibrations to the internal ear ; but while we are accus- 

 tomed to look upon this arrangement of the parts as 

 presenting us with a greater perfection of the auditory 

 apparatus than is present in the lower forms, it is not 

 by any means proven that such is the case, for this 



