194 



PHYSIOLOGY 



CHAT. 



the scala vestibuli, opens into the vestibule. At the apex of the 

 cochlea the two communicate by a small opening (helicotrema). 



Between the two scalae is a smaller canal, triangular in section, 

 the scala media, or ductus cochlearis (canal of the cochlea), which 

 is bounded by the slender membrane of Ueissner facing the 



scala vestibuli, and the spiral or basilar membrane 



tacing 



the 



..Is 



ms 



Fie. "">. Si-ctkm thnm^h cochlea nt tin- cat. Maxnilied -"> cliaiiu't.-i >. (Snliutta.) '/.'.. duct of 

 cochlea; \i.*., :_ r anxli"ii sjiirale ; Co., bony wall of cochlea; l.s., li<;arnentuni siiirali- ; ni.s., 

 nuMnbraiia .sjiiialis ni liasilaris, .sii|)]MHtiii- <>i uan of Corti ; m.i:, nicinlnaiui \fstibularis or 

 Ueissn.T's iiii-iiibraiii- ; N.c., ni-i-vus cm-hli-ai is ; -.,., scala vrstibnli ; f.t., scala 



scala tympani. This canal contains the endolymph of ihe^ mem- 

 branous labyrinth of the cochlea, and within it and just above the 

 basilar membrane is the very delicate organ of Corti, the terminal 

 apparatus of the cochlear nerve. As shown by Fig. 75 the cochlear 

 nerve penetrates the central canal of the modiolus, and sends its 

 branches along the osseous spiral lamina to the basilar membrane 

 and the organ of Corti. 



