THE INTERNAL EAR 



695 



the endolympli; they do not entirely fill the bony cavity of the labyrinth 

 in which they lie, the intervening space being occupied by a retiform 

 connective tissue with broad interstices which are permeated by an 

 aqueous fluid, the perilymph. 



THE SACCULE 



The saccule is a rounded membranous cavity which is connected, 

 on the one hand, by means of the slender canalis reuniens, 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 



FIG. 579. DIAGRAM OF THE MEMBRANOUS LABYRINTH IN LATERAL VIEW. 



A, ampullae; U, utricle; S, saccule; SM, scala media or cochlear duct; CR, canalis 

 reuniens; C, crus, or common canal; SE, saccus endolymphaticus; DE, ductus endo- 

 lymphaticus; dss, dsp, dsl, superior, posterior and lateral (external) semicircular 

 ducts. The utricle and saccule are connected by the utriculosaccular duct. The 

 cochlear duct terminates in the ceca vestibulare and cupulare. (After Gray.) 



ectodermal epithelium, a membrana propria and a fibrous coat. The epi- 

 thelium consists of flattened squamous cells; it completely lines the 

 cavity. The epithelial surface is somewhat irregular from the papillary 

 elevations of the fibrous coat. On the antero-inferior surface of the sac- 

 cule the epithelium is peculiarly altered so as to form a layer of col- 

 umnar cells, many of .which are provided with stiff cilia. This neuro- 

 epithelium is distributed over an oval area (3 mm. by 2 mm. in extent) 

 beneath which the fibrous coat is much thickened by the entrance of 

 many fibers derived from the vestibular portion of the acoustic nerve. 



