364 MANUAL OF HISTOLOGY. 



there can be shown, by means of the silver method, a layer of 

 endothelium. This proves that the canals are of the nature of 

 serous cavities. 



The lamina spiralis is composed of an osseous and a mem- 

 branous portion. The osseous portion reaches about one-half 

 the distance from the modiolus to the opposite wall, and on its 

 outer and vestibular portion is a mass of connective tissue 

 called crista spiralis (Fig. 163, Or.), the upper lip of which is 

 called labium vestibulare (Fig. 163, Lv.\ while the lower lip is 

 called labium tympanicum (Fig. 163, Lt.}; the space between the 

 two lips has received the name of recessus internus. The crista 

 spiralis is divided by a number of parallel furrows, which gives 

 the surface a regular toothed appearance when seen from the 

 vestibular surface. Hence, the portions between the furrows 

 are called "auditory teeth." 



The under (vestibular) of the two lips is connected with 

 the membrana basilaris (Fig. 163, Hn, Zp'\ which is com- 

 posed of two layers of finely fibrillated connective tissue, 

 and is covered on its tympanic surface by a layer of endothe- 

 lium, and on the surface turned toward the ductus cochlearis 

 l)y the organ of Corti and its supporting cells. The inner 

 layer of this fine connective tissue is directly continued into 

 the bases of the pillars of the organ of Corti next to be de- 

 scribed. 



The organ of Corti, so named from its discoverer, is a com- 

 plicated arrangement of cells in which the nerve terminates, 

 and of other cells and their modifications, which apparently 

 act as supports to these and as modifiers of the sound. The 

 cells proper, in which the nerve terminates, have received the 

 name of hair-cells, from the ciliated appendages which they 

 carry (Fig. 163, a, a" , a", a"), while the peculiar modified cells 

 which are their chief support are called the pillars. 



The pillars (Fig. 163, ft, fa} are two slender, slightly shaped 

 bodies, of a finely fibrillated structure, showing, however, in 

 their early stages, the presence of nuclei. They stand upon 

 the membrana basilaris, and are apparently to be directly fol- 

 lowed into the fine layer of connective tissue beneath them. 

 They are arranged in two rows, named inner and outer, ac- 

 eording to their situation as regards the modiolus. The pillars 

 are inclined toward each other, and the space between them is 

 named the tunnel. The head of the outer is a little enlarged 



