THE ORGAN OF HEARING. 305 



in common with the rods of Corti, being specialized epithelial 

 cells which extend the entire thickness of the epithelial stratum to 

 terminate in the peculiar end-plates or phalanges. It follows that 

 while the free surface of Corti' s organ is composed of both auditory 

 cells and sustentacular cells, the elements resting upon the basi- 

 lar membrane are of one kind alone, the cells of Deiters. The 

 bodies of the latter consist of two parts, the elongated cylindri- 

 cal chief portion of the cell, containing the spherical nucleus 

 and resting upon the basilar membrane, and the greatly-attenuated 

 pyramidal phalangeal process. A system of communicating 

 intercellular clefts, the spaces of Nuel, lies between the auditory 

 and supporting cells ; these are occupied by a semi-fluid inter- 

 cellular substance, like the tunnel of Corti, which they connect. 



The membrana tectoria, or Corti's membrane, stretches from 

 the upper lip of the limbus above the sulcus spiralis and Corti's organ as 

 far as the last row of the outer hair-cells. The membrane is a cutic- 

 ular production originally formed by the cells covering the region of 

 the auditory teeth and the spiral sulcus ; at first it rests upon the 

 epithelial cells, but later it becomes separated from those lying external 

 to the free edge of the auditory teeth and assumes its conspicuous posi- 

 tion over the organ of Corti. The membrane seems to be composed of 

 fine resistant fibres held together by an interfibrillar cement-sub- 

 stance. During life the membrane is probably soft and gelatinous 

 and much less rigid than its appearance after reagents indicates. 



The outer sustentacular cells, or cells of Hensen, form an 

 outer zone immediately external to the last Deiters' s cell ; these ele- 

 ments resemble the inner sustentacular cells, but differ somewhat in 

 form and arrangement. In consequence of their oblique positions 

 the bodies are not only greatly elongated but also imbricated. 



The cells of Claudius are the direct continuations of Hensen' s 

 cells, and pass uninterruptedly into the low columnar elements 

 covering the remaining part of the basilar membrane. These cells 

 possess clear faintly granular protoplasm, in which pigment- 

 granules are frequently seen as well as spherical nuclei. At the 

 outer extremity of the basilar membrane these cells are continuous 

 with the epithelium covering the upper surface of the basilar crest. 



The nerves of the cochlea, branches of the cochlear division 

 of the auditory nerve, present an intricate arrangement, the exact 

 mode of their ultimate termination being still in many points un- 

 certain. With the exception of bundles for the supply of the first 

 turn, which run in channels leading directly to the peripheral 

 spiral canal, the cochlear nerves pass into the central canal of the 

 modiolus, from which a series of large-sized lateral branches diverges 

 at quite regular intervals through canals communicating with the 



