1G8 HEARING AIDED BY THE OTHER SENSES. 



control of any muscles by which it is relaxed or made 

 tense, according to the graveness or acuteness of the 

 sounds, as has been conjectured, is a fact on which we 

 have no positive information. Vibrations are produced 

 in the chain of small bones, and in the walls of the tym- 

 panum, and thence transmitted to the auditory nerve. 

 The essential part of the organ of hearing, is the cavity 

 containing the soft pulp, in which the auditory nerve is 

 distributed. This is found wherever the sense exists, 

 and where none of the other parts are present, as in 

 some of the lower orders of animals. 



Emily. And is this sense, Dr. B., as much under 

 the influence of habit, as that of sight ? 



Dr. B. Certainly ; hearing makes us acquainted 

 only with the existence of sounds our knowledge of 

 their distance, direction and nature, is obtained by ex- 

 perience, and the assistance of the other senses. Our 

 knowledge of their direction, seems to depend chiefly on 

 the harmony existing between both ears. If we close 

 one ear, and a noise be made at a little distance from 

 us, it is often impossible to determine whence it comes, 

 though with both ears open, we might not be at any loss 

 to determine. We are considerably assisted also in our 

 judgment of the direction of sounds, by the sight, for in 

 the dark, we often find it very difficult to tell from what 

 point it comes. We judge of the distance of sounds too, 

 by having been long familiar with them, and by fre- 

 quently comparing them together. 



Emily. I am conscious how liable we are to be de- 

 ceived respecting the direction and distance of strange 

 sounds I have often been deceived in this way, my- 

 self. . Do we not judge of the distance of some sounds 

 also, by their peculiar tone, and when this tone is imi- 

 tated, are we not easily deceived ? 



Dr. B. Of a truth we are, and this is the secret of 

 the ventriloquist's deception, but more of that by-and- 



b >'- 



Emily. Cannot some people perceive certain sounds 



