698 



THE EAK 



with a reticulated cuticular membrane which presumably is formec by 

 the amalgamation of the free ends of the sustentacular cells. Through 

 the openings in this reticular membrane the ciliary tufts of the hair 

 cells project. 



The central ends of the hair cells, beneath the nucleated enlarge- 

 ment which is found near the middle of the epithelial layer, are pro- 

 longed outward between the nucleated portions of the sustentacular cells 

 and frequently terminate in small knobbed extremities. This portion 

 of the cells is in intimate relation with the terminal fibrils of the vestibu- 

 lar portion of the acoustic nerve, which, coming from a nerve plexus in 



the fibrous wall of the saccule, 

 forms an intra-epithclial plexus 

 of delicate varicose fibrils. Fre- 

 quently the epithelial coat con- 

 tains coarse granules of a brown- 

 ish pigment which, at times, also 

 produces a diffuse coloration of 

 the cells. 



The lining epithelium of the 

 saccule rests upon a thin homo- 

 geneous basement membrane and 

 is further supported by a delicate 

 fibrous coat or tunica propria. 

 The connective tissue of this coat forms interlacing bundles the most 

 of which are distributed in a circular manner about the wall of the 

 ovoid sacculus. At the macula this coat is much thickened by the en- 

 trance of the fibers from the vestibular nerve. It also contains the 

 minute blood-vessels which supply the organ. 



As is the case with the other divisions of the membranous labyrinth, 

 the fibrous wall of the saccule is in contact on one aspect of its surface 

 with the periosteum which lines the osseous labyrinth; elsewhere it is 

 separated from the periosteum by the perilymphatic cavity. 



FIG. 583. NERVE ENDINGS IN THE 

 MACULA ACUSTICA OP A GUINEA-PIG. 



a, epithelium; b, tunica propria; c, three 

 terminal nerve fibers. Golgi stain. X 

 about 200. (After Retzius.) 



THE UTRICLE 



The utricle is somewhat larger than the saccule. It lies behind 

 and somewhat above the saccule, is of a very irregular oblong form, 

 and receives the insertions of the semicircular canals. Its anterior 

 portion is provided with a macula and the structure of its wall 

 differs in no wise from that of the saccule; both of these mem- 



