520 



STUDIES IN ADVANCED PHYSIOLOGY. 



basilar membrane consists of about 3,000 such strings laid 

 side by side. Other things being equal the lengths of these 

 individual strings will determine the pitch of their vibra- 

 tions, so that the basilar membrane has its high strings 

 near the base of the cochlea, its low ones near the top. 

 This basilar membrane is, in fact, the sounding-board of 

 the ear, and the various strings of this sounding-board are 

 set up in sympathetic vibrations by the sound waves which 

 pass through the cochlea. 



It will be remembered that the sound waves from the 

 vestibule ascend the cochlea through the scala vestibuli, 

 and while ascending this they do not affect the basilar mem- 



Fig. 162. SECTION ACROSS THE BASAL TURN OF THE HUMAN COCHLEA. (After Retzius.) 

 D. C, scala media; s. v, scala vestibuli; s. t, scala tytnpani; R, membrane of Reissner; 

 Mt, tectorial membrane ; 6. m, basilar membrane ; t C, tunnel formed by the rods of Corti ; 

 n, nerve; sp. I, spiral lamina; sp, sulcus spiralis; 1. sp, spiral ligament; I, limbus; h, i, 

 inner hair cells; h, e, outer hair cells, with hairs from same projecting through the reticu- 

 lar membrane. 



brane, as the membrane of Reissner intercepts. At the top 

 of the cochlea the sound passes into the scala tympani, and 



