XXX. THE SPECIAL SENSES {concluded). 

 Auditory Sensations. 



As with "visual sensations the sensory fibers of the nerves 

 of hearing have their endings in a pair of external organs 

 called the ears. By means of these ears the waves of sound 

 are made to produce impulses of hearing just as the eyes 

 transform waves of light into visual impulses. 



Structure and form of the ears. — The ears are to exter- 

 nal appearance merely two twisted flaps of skin-covered 



Endolymphatio 

 Duct 



,'Saccule 



Eustachian Tube 



Pig. 223 — Diagram of the ear. 



^^^^^ Vestibular Passage 

 <^^Tjimpanio Passage 

 Fenestra Rotunda 



cartilage attached one on each side of the head. These 

 external flaps are, however, only the external parts of the 

 organ whose sensitive parts are embedded in cavities of 

 the temporal bones. For convenience in description, we 

 divide the ear into three parts, which we call the external 

 ear, the middle ear, and the inner ear. Since both ears are 



470 



