390 



NORMAL HISTOLOGY. 



membrane or tympanic wall of the duct is attached. Near the base 

 of the basilar crest the outer wall of the cochlear duct is marked by 

 an additional smaller projection, the prominentia spiralis, or 

 accessory spiral ligament, distinguished usually by the presence 



FIG. 401. 



Section of single turn of cat's cochlea : SV, SM, ST, scala vestibuli, media, and tympani ; 

 a, osseous tissue projecting as spiral lamina (6) ; c, basilar membrane attached to spiral liga- 

 ment (ft) on outer wall ; e, concave surface lined by flat cells (q) interrupted by spiral promi- 

 nence (/) containing blood-vessel ; g, stria vascularis ; h, Reissner's membrane covered by 

 epithelium (/) of cochlear duct and by endothelium () of scala vestibuli ; i, limbus from 

 which extends membrana tectoria (ft) overhanging Corti's organ ; m, tunnel of Corti ; r, s, 

 inner and outer hair-cells ; p, cells of Claudius ; n, spiral ganglion ; o, nerve-bundles ; z/, 

 blood-vessel. 



of several small blood-vessels. The part of the wall lying be- 

 tween this prominence and the point of attachment of Reissner's 

 membrane is occupied by a peculiar vascular structure, the stria 

 vascularis. 



The epithelium covering the outer wall of the cochlear duct 

 varies in different positions ; the usual low flat cells become higher 

 and more cuboidal within the area corresponding to the stria vas- 

 cularis ; over the prominence the cells again become flat and poly- 

 hedral, but increase in height on approaching the basilar membrane. 



The stria vascularis is remarkable on account of the existence 

 of capillary blood-vessels within an epithelial structure. The 

 presence of numerous vessels within the area is readily established, 



