CHAPTER XXII 



THE EAR 



Tin; ear contains the 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 



FIG. 38. DIAGRAMMATIC VIFAV OF THE ORGANS OF THE KAR. 



(After Helmholtz.) 



/), external auditory canal; cc, membrana tympani; />/>', cavity of the tym- 

 panum with the auditory ossicles; 0, fenestra ovalis; r, fenestra rotunda; ./, 

 cochlea; A', Kustachian 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 



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