194 



PHYSIOLOGY 



CHAP. 



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 Reissner facing the 

 scala vestibuli, and the spiral or basilar membrane facing the 



Co 



FIG. 7o. Section through cochlea of the cat. Magnified 25 diameters. (Sobotta.) d.c., duct of 

 cochlea; g.s., ganglion spirale ; Co., bony wall of cochlea; l.s., ligainentum spirale ; m.s., 

 membrana spiralis or basilaris, supporting organ of Corti ; m.v., membrana vestibularis or 

 Itcissncr's membrane ; JV.c., nervus cochlearis ; *. r., sc;ila vestibuli ; s.t., scala tympani. 



scala tympani. This canal contains the endolymph of the 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. 



