No. 6.] NERVE ENDINGS IN THE HUMAN EAR. 277 



the parts of the cochlea. These layers are quite distinct, and 

 are arranged as follows : an upper and a lower layer of fine 

 fibers inclosing between them a layer of fibers. The important 

 imperfect layer of spiral fibers is most apparent upon the upper 

 surface of the basilar membrane. The basilar fibers are the 

 direct product of a part of the connective tissue cells of the 

 embryonic basilar membrane which have been transformed into 

 long cylindrical fibers, for the most part simple, but occasionally 

 branched. 



Auditory Cells. 



The hair-bearing acoustic cells are cylindrical in shape, those 

 of the inner row being shorter cylinders, so short, in fact, that 

 they become ovoidal. They are surrounded and supported by 

 the peculiarly modified non-nervous cells of the organ of Corti. 

 The hair cells are much shorter than the supporting elements, 

 and do not reach the basement membrane, or, as it is called, 

 the basilar membrane, a fact of much significance in view of 

 certain physiological hypotheses. 



The hairs arise from the top of each cell as a slender bundle, 

 the fibrils growing from all parts of the cell cap, not forming, 

 as some assert, a crescentic or horseshoe-shaped outline upon 

 the cell cap. Each cell bears on an average two dozen deli- 

 cate, flexible filamentous hairs, which sweep inwards from the 

 cell to end free in the endolymph above the limbus spiralis. 

 The whole hair is thus supported by, or floats in the endolymph, 

 and all the hairs from the aggregate of hair-bearing cells are 

 so closely placed that they exert a capillary attraction upon 

 each other, and thus, when they are loose from the tops of the 

 cells, they remain adhering in the form of a long band or 

 ribbon which has been called the membrana tcctoria or damper, 

 from its supposed role in auditory physiology. The long hairs 

 are the percipient elements in the cochlea instead of the con- 

 nective tissue fibers of the basement membrane of the sense 

 organ, and the ear thus agrees with the eye, the nose, and 

 other sense organs in the disposition of its percipient, recipient, 

 and transmitting apparatus. 



