THE INTERNAL EAR 



619 



utriculo-saccular canal, from which a much prolonged diverticulum 

 enters the aqueductus vestibuli to penetrate to the posterior surface 

 of the petrous bone where it comes into relation with the cerebral 

 meninges ; this diverticulum is known as the ductus endolymphati- 

 cus. The utricle and saccule, as also all other portions of the 



FIG. 450. THE BONY LABYRINTH. 



7, round window ; 2, osseous lamina spiralis ; <?, osseous cochlear canal ; 4, fl r of 

 internal auditory meatus ; 5, vestibule ; , 7, <!?, P, semicircular canals. The figures are 

 placed at that portion of the margin which is nearest the structure indicated. (After 

 Kiidinger.) 



membranous labyrinth, contain a watery fluid, the endolyinph ; 

 they do not entirely fill the bony cavity of the labyrinth in which 

 they lie, the intervening space being occupied by a retiform con- 

 nective tissue with broad interstices which are permeated by an 

 aqueous fluid, the perilymph. 



The saccule is a rounded membranous cavity which is connected, 

 on the one hand, by means of the slender canalis reiiniens, with 

 the cochlear duct or scala media, and on the other hand with the 

 ductus endolymphaticus and utricle, as already stated. Its wall 

 consists of an endothelium, a membrana propria and a fibrous coat. 

 The endothelium consists of flattened squamous cells ; it com- 

 pletely lines the cavity. The epithelial surface is somewhat irreg- 



