THE SENSE OF HEARING 723 



The Functions of the Internal Ear. From the anatomic arrange- 

 icnt of the structures of the internal ear it is evident that if the vibrations 

 I the stapes bone are to reach the peripheral organs the hair cells of 

 ,oth the vestibular and cochlear nerves, they must traverse successively 

 he perilymph, the membranous walls, and the endolymph. As the penlymph 

 3 incompressible, the inward movement of the stapes would be prevented 

 vere it not for the elastic character of the membrane closing the foramen 

 otundum The pressure wave occasioned by each inward movement of 

 stapes is transmitted through the scala vestibuli, the helicotrema, and 

 ; cala tympani, to this membrane, which by virtue of its elasticity is pressed 

 nto the tympanic cavity. With the outward movement of the stapes, 



^ThTFunctionTof thVcoclilea.-The cochlea is the portion of the in- 

 ternal ear which is concerned in the perception of tones. The arrangement 

 oHhe histologic elements of the organ of Corti indicates that they m some 

 way respond To the vibrations of varying frequency and *rm and through 

 Ae development of nerve impulses, evoke the sensations of pitch and quality. 

 The manner in which this is accomplished is largely a matter of speculation. 

 While many theories have been offered in explanation of the power to distm- 

 S thtpLh and the quality or timbre of a tone most physiologists prefer 

 ETof Helmholtz, who regarded the transverse fibers of *e basilar mem- 

 Trane as the elements immediately concerned, and compared them both in 





