632 THE EAR 



undifferentiated basilar portion occupies only the deeper half of the 

 pillar cell. 



Tfie outer hair cells form three to five rows of ciliated cells 

 which are similar in structure to the inner hair cells, and which 

 are supported by the sustentacular cells of Deiters. Their cylin- 

 drical cell bodies occupy the superficial third of the epithelial .layer 

 and at the deeper extremity present a nucleated enlargement, 

 beyond which they are continued only as a slender basal process. 

 The free ends of the outer hair cells present an expanded oval sur- 

 face from which the cilia project. 



The outer sustentacular cells (Deiters 9 cells) are cylindrical cells 

 whose expanded bases rest upon the basal membrane and whose dis- 

 tal portions extend toward the surface between the outer hair cells. 

 The superficial portion of these cells, being encroached upon by 

 the broad outer hair cells, is very slender ; the broader basal portion 

 occupies the deeper two-thirds of the neuro-epithelium, the sphe- 

 roidal nuclei being found at the level of the middle third. Each 

 sustentacular cell contains a cuticular filament which begins in con- 

 tact with the cuticle of the basal membrane, and extends through 

 the axis of the cell to its free border, where it expands to form 

 a broad flattened plate of peculiar shape, known as the phalangeal 

 process. These cuticular processes surround and overlie the margins 

 of the head plates of the hair cells, thus forming a reticular layer 

 through the openings of which the cilia of the hair cells project. 



The cells of Deiters are succeeded by the sustentacular cells of 

 Hensen, tall columnar cells about eight rows broad, the first of 

 which equal in height the tall cells of the preceding type, but 

 which at their outer border become abruptly shortened, pass into 

 the cuboidal cells of Claudius, and are thus continued outward to 

 the spiral ligament. 



The nuclei of the cells of Hensen are found in their superficial 

 third, those of the cells of Claudius in the center of the cell. Be- 

 neath Hensen's cells other small nucleated elements are occasionally 

 found ; they give to this layer somewhat the appearance of a two- 

 rowed epithelium and are known as the cells of Bdttcher. 



Both the cells of Hensen and those of Claudius are provided 

 with a cuticular margin which, with the similar cuticle of the cells 

 of Deiters, forms a continuous, membranous, cuticular layer known 

 as the lamina reticularis. The inner portion of this cuticular 

 membrane is pierced by the cilia of the three to five rows of outer 

 hair cells, as already described. 



