422 ORGANS OF THE SENSES. 



the functions of these various parts of the internal ear. It 

 has been remarked that the cochlea appears to be necessary 

 to animals that hear by means of vibrations of air, and that, on 

 the other hand, a sonorous larynx, which is capable of emit- 

 ting musical sounds, is generally found to exist with ;t, while 

 also accompanied by a sensibility in the animal to musical 

 sounds : it thus appears to be the chief organ of musical 

 perception, and the calculation which has been made of the 

 number of elements in the organ of Corti, compared with 

 the scale of musical notes, seems to confirm this view. It 

 has also been suggested that the vestibular chamber may 

 possess the power of judging more.especially of the intensity 

 of notes, and even of sounds, and that the three semicircu- 

 lar canals may, by means of their triple arrangement of 

 position, horizontal and transverse, vertical and longitudinal, 

 and horizontal, have the faculty of judging of the direction 

 of sounds ; we have, however, already seen that the pinna of 

 the ear has also the property of defining the direction of 

 sounds. 



"Whatever be the special function of each part of the inter- 

 nal ear, the shock upon the terminal organs of the nerves 

 always enables us to distinguish several special conditions in 

 the sound waves, which the science of physics shows to be 

 the cause of the difference in sounds. The fulness of these 

 vibrations is what constitutes the force or intensity of sounds, 

 while their rapidity, or number in a certain space of time, 

 constitutes the acuteness or gravity of sounds, and enables us 

 to distinguish the sounds in a perfect scale from the lowest 

 (32 vibrations in a second) up to the highest (76,000 vibra- 

 tions in a second). Finally, we distinguish in sounds a 

 special quality -called their tone; this is more difficult to 

 define, but appears to consist of the sound resulting from the 

 combination of several notes, whose tone is different, accord- 

 ing to the varieties of the combination. (See Phonation, p. 

 359.) Habit certainly enables us to judge of the nature of 

 the vibrating body by its tone, which constitutes what might 

 be called, in a physiological point of view, the savour of a 

 sound ; by this we recognize the voice of a person, judge of 

 the sex by the voice, and even judge of the sentiments of the 

 speaker ; in all these cases, although the sounds may be of 

 the same intensity and pitch, they are produced by .different 

 combinations of the same simple sounds'; the waves produced 

 have, therefore, a different form, and in judging of the tone 

 of a note, we may be said to judge of the/orm of the vibra- 



