ORGANS OF SPECIAL SENSE. 



367 



The modiolus, or columella, is broad at the base, but tapers 

 gradually toward the apex, where it terminates within the last 

 turn or cupola in the infundibulum, a funnel-shaped lamina of 

 bone. Its interior is traversed by numerous canals for vessels 

 and nerves, one of which the canalis centralis modioli runs 

 nearly the whole length, and transmits the arteria centralis 

 modioli. 



Lamina spiralis, the partition between the two tubes, con- 

 sists of two thin laminae of bone filled with cancellous tissue 



FIG. 165. 



Organ of Corti. N, cochlear nerve; K, inner and, P, outer hair- 

 cells; n, nerve-fibrils terminating in P; a, a, supporting cells; d, cells 

 in sulcus spiralis; z, inner rod of Corti; Mb. Corti, membrane of Corti, 

 or the membrana tectoria; o, the membrana reticularis; H, G, cells 

 filling up the space near the outer wall. (Bocnuiny.) 



lamina spiralis ossea projecting from the modiolus half-way to 

 the outer wall, the lamina being completed by the membrana 

 lasilaris. The osseous lamina terminates in the cupola in a 

 hook-like process the hamulus. 



The spiral canal, between the modiolus and the outer wall, 

 is divided by the lamina <pi rails ossra and nuMiilirana basilaris 

 into two canals, or scales- -the upper scala vestibuli, and the lower 

 scala tympani. 



