EAR 



473 



hemispherical papillae covered with simple flat epithelium, found within 

 the cochlear duct near the vestibular membrane. Further within the 

 cochlear duct the papillae give place to a single row of flat ridges or plates, 

 directed peripherally. These are "Huschke's auditory teeth" (Fig. 480). 

 Beneath them the limbus terminates abruptly in an overhanging labium 

 vestibulare, which projects over an excavation the sulcus spiralis (Fig. 

 478). The basal wall of the sulcus is the labium tympanicum, found at 

 the peripheral edge of the osseous spiral lamina. As the epithelium of 

 the limbus passes over the labium vestibulare into the sulcus, it becomes 

 cuboidal. A remarkable non-nucleated structure projects from the labium 



Membrana tectoria. 



Capillaries of the 



Labium vestibulare. 



Nerve bundle. 



FIG. 478. PORTION OF FIGURE 477. 



Deiter's Membrana Connective 



- cells. basilaris. tissue. 



Pillar cells. 

 X 240. x, Intercellular "tunnel" traversed by nerve fibers. 



vestibulare over the neuro-epithelium of the membranous spiral lamina. 

 It is called the membrana tectoria and is considered to be a cuticular for- 

 mation of the labial cells to which it is attached. Hardesty describes 

 it as composed of "multitudes of delicate fibers of unequal length, em- 

 bedded in a transparent matrix of a soft, collagenous semi-solid character, 

 with marked adhesiveness" (Amer. Journ. Anat., 1908, vol. 8, pp. 109-179). 

 The lamina spiralis membranacea, or lamina basilaris, consists of four 

 layers. The mesenchymal epithelium of the scala tympani is followed by 

 a layer of delicate connective tissue, prolonged from the periosteum of the 

 scala. Its spindle cells are at right angles with the fibers of the overlying 

 membrana basilaris. This membrane, which is beneath the epithelium of 

 the cochlear duct, consists of coarse straight fibers extending from the labium 

 tympanicum to the ligamentum spirale. They cause it to appear finely 

 striated (Fig. 479). Peripherally (beyond the bases of the outer pillar 

 cells) the fibers are thicker, and are called "auditory strings"; they are 



