COCHLEA. 387 



spherical papillae found within the cochlear duct near the vestibular 

 membrane. Further within the ductus cochleae there is a row of flat 

 elongated forms directed from the modiolus toward the periphery; these 

 are sometimes called Huschke's auditory teeth (Fig. 438). The papillae 

 are covered by a simple layer of flat epithelium. As the limbus extends 

 from the vestibular membrane toward the peripheral part of the cochlea, 

 it terminates abruptly in an overhanging labium ITS fibula re beneath which 

 is an excavation, the siilcns spiralis (Fig. 436). 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 

 formation, non-nucleated, soft and elastic, projects from the labium ves- 

 tibulare over the neuro-epithelium of the membra- 

 nous spiral lamina. It is called the membrana lector ia 

 and is considered to be a cuticular formation of the 

 labial cells to which it is attached. 



The lamina spiralis membranacea, or lamina basil- 

 aris (?), consists of four layers. The mesenchymal ^~^~^ 



epithelium of the sea la tympani is followed by a layer 

 of delicate connective tissue prolonged from the peri- FIG. 437. SURFACE 



11 -l VIEW OP THE 



osteum of the scala. Its spindle cells are at right LAMINA SPIRALIS 



MEMBRANACEA OF 



angles with the fibers of the overlying membrana * CAT - x ?4- 



3 Drawn with 



basilaris. This membrane, which is beneath the change of focus. 



e, Epithelium (cells of 



epithelium of the cochlear duct, consists of coarse Claudius) of the 



ductus cochleans 



-traight fibers extending from the labium tympanicum 



to the ligamentum spirale. They cause it to appear 



finely striated (Fig. 437). Peripherally (beyond the 



bases of the outer pillar cells) the fibers are thicker 



and are called "auditory strings"; they are shortest in the basal part 



of the cochlea and longest toward the apex, corresponding in length with 



the basal layer of the cochlear duct. These fibers have been thought 



to vibrate and assist in conveying sound waves to the nerves. 



The epithelial cells covering the basilar layer, present rows of highly 

 modified forms extending up and down or lengthwise of the cochlear duct, 

 and constituting the spiral organ [of Corti]. Next to the cuboidal epithelium 

 of the sulcus spiralis there is a single row of inner hair cells (Fig. 436). 

 These are short columnar cells which do not reach the bottom of the epi- 

 thelium; each has about forty long stiff hairs on its free surface. The 

 inner hair cells are followed peripherally by two rows of pillar cells, the 

 inner and outer, which extend the whole length of the cochlear duct. As 

 seen in cross section they are in contact above, but are separated below 



