442 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



pies the postero-superior portion of the bony vesti- 

 bule. It communicates by five apertures with the 

 membranous semicircular canals. Its wall is com- 

 posed of fibrous tissue, lined internally with a single 

 layer of columnar epithelium. The floor and an- 

 terior wall is thickened to form the macula acustica 

 utriculi, which is innervated by fibers of the auditory 

 nerve. The epithelium of this region is composed 



Ant. semicircular canal. 



Auditory nerve 

 with its vestibu- 

 larand cochlear 



Fig. 305. Membranous labyrinth of the right ear from five-months hu- 

 man embryo (from Schwalbe, after Retzius). 



of two kinds of cells: (i) slender sustentacular cells 

 resting on a basement membrane, and (2) hair cells, 

 or auditory cells. The latter support a number of 

 stiff hairs and constitute the neuro-epithelium, 

 around which arborize the neurons of the auditory 

 nerve. Crystals of calcium carbonate, known as 

 otoliths, are found on the surface of the epithelium. 

 The sacculus occupies the lower portion and fore 



