848 



SPECIAL SENSES. 



of the pillars, or rods of Corti. They are nearly homogeneous, except when treated with 

 reagents, and are said to be of about the consistence of cartilage. They are closely set 

 together, with very narrow spaces between them, and it is difficult to see how they can 

 be stretched to any considerable degree of tension. The arch is longer at the summit 



Fio. 26S. The two pillars of the organ of Corti. (Sappey.) 



A, external pillar of the organ of Corti : 1, body, or middle portion ; 2, posterior extremity, or base ; 8, cell on its in- 



ternal side ; 4, anterior extremity ; 5, convex surface by which it is joined to the internal pillar ; 6, prolongation 

 of this extremity. 



B, internal pillar of the organ of Corti : 1, body, or middle portion ; 2, posterior extremity ; 8, cell on its external side; 



4, anterior extremity; 5, concave surface by which it is joined to the external pillar; 6, prolongation, lying above 

 the corresponding prolongation of the external pillar. 



C, the two pillars of the organ of Corti, united by their anterior extremity, and forming an arcade, the concavity of 



which presents outward : 1, 1, body, or middle portion of the pillars ; 2, 2, posterior extremities ; 3, 3, cells at- 

 tached to the posterior extremities; 4, 4, anterior extremities joined together; 5, terminal prolongation of this 

 extremity. 



than at the base of the cochlea, the longest rods, at the summit, measuring about -yfa of 

 an inch, and the shortest, at the base, about -^-^ of an inch. As we before remarked, the 

 relations between the pillars and the terminal filaments of the auditory nerves are not 

 definitely settled. 



In addition to the pillars just described, various cellular elements enter into the struct- 

 ure of the organ of Corti. The most important of these are the inner and the outer hair- 



FIG. 269. Vertical section of the organ of Corti of the dog; magnified 800 diameters. (Waldeyer.) 

 o^&, homogeneous layer of the basilar membrane ; u, tympanic layer, with nuclei, granular cell-protoplasm, and con- 

 nective tissue: !, tympanic lip of the crista spiralis; c, thickened portion of the basilar membrane ; d, spiral 

 vessel ; e, blood-vessel ; f\ h, bundle of nerves ; Q, epithelium ; i, inner hair-cell, with its basilar process, Jc ; I, head- 

 plate of the inner pillar; m, union of the two pillars; n, base of the inner pillar; o. base of the outer pillar; p, q, 

 r, outer hair-cells, with traces of the cilia; t, bases of two other hair-cells; z, Hensen's prop-cell; W x , lamina 

 reticularis ; w, nerve-fibre passing to the first hair-cell, p. 



cells. The inner hair-cells are arranged in a single row, and the outer hair-cells, in three 

 rows. Nothing definite is known of the function of these cells. The relations of these 

 parts are shown in Fig. 269, which is rather complex, but, on careful study, gives a good 



