CHAPTER XXII 



THE EAR 



THE ear contains fehe sense organ of hearing and the 

 organ for perceiving the positions and movements of the 

 head. 



1. THE AUDITORY ORGAN 



The adequate stimuli for the auditory organ are the vibra- 

 tions of solid, liquid, or gaseous bodies, called sound waves, 

 because by their action upon the auditory organ they give 

 rise to the sensation of sound. These vibrations are usually 



'E 



FIG. 38. DIAGRAMMATIC VIEW OF THE ORGANS OF THE EAR. 



(After Helmholtz.) 



Z>, external auditory canal; cc, membrana tympani; BB, cavity of the tym- 

 panum with the auditory ossicles; o, fenestra ovalis; r, fenestra rotunda; A, 

 cochlea; E, Eustachian tube. 



carried to the ear by air. But the vibrations can also be 

 carried to the ear through the bones of the head, as when 



285 



