620 



THE EAR 



ular from the papillary elevations of the fibrous coat. On the 

 antero-inferior surface of the saccule the epithelium is peculiarly 

 altered so as to form a layer of columnar cells, many of which are 

 provided with cilia. This neuro-epitlielium is distributed over an 

 oval area beneath which the fibrous coat is much thickened by the 

 entrance of many fibres derived from the vestibular nerve. This 

 elevation with its neuro-epithelial covering is known as the macula 

 sacculi. 



The neuro-epithelium contains two varieties of cells, the sus- 

 tentacular and the hair cells. The former, fibre cells of Retzius, 



FIG. 451. THE ISOLATED MEMBRANOUS LABYRINTH. 



J, utricle; , saccule (opened) ; .?, location of the macula sacculi ; 4, ampulla of a semi- 

 circular canal; 5, canalis communis. Low magnification. (After Klidinger.) 



form a layer, two or three cells deep, which rests upon the base- 

 ment membrane, and whose broad basal portion contains a sphe- 

 roidal nucleus. Beyond the nucleated portion the cytoplasm of the 

 sustentacular cell is continued inward between the bodies of the 

 hair cells to the surface of the epithelial layer, this portion of the 

 cell being relatively slender. 



The hair cells occupy the superficial part of the epithelial layer 

 by their broad nucleated portions, which carry upon their free 



