482 



THE ORGAN OF HEARING. 



1. UTRICULUS AND SACCULUS. 



Only the inner wall of the utriculus is connected with the peri- 

 osteum of the vestibule. In this region lies the corresponding 



Membranous semicircular canal. 



fjf/v-"t . . f 



'/ "^ ''.''/' ^S&S* - . Epithelium of the 



i' ;" V-' :'-'fc-*~'.^ i -(..J' membranous 



Blood-vessel. 



Wall of mem 



branous 



canal. f 



canal. 



''./ Ligament of 



. canal. 



Perilymphatic 

 spaces. 



Blood-vessel. 



Fig. 370.- Transverse section through an osseous and membranous semicircular canal 

 of an adult human being; X 5 (after a preparation by Dr. Scheibe): a, Connective- 

 tissue strand representing a remnant of the embryonic gelatinous connective tissue. Such 

 strands serve to connect the membranous canal with the osseous wall. 



macula cribrosa, through which the nerves penetrate to the macula 

 of the utriculus. The utriculus and sacculus fill only a part of the 

 inner cavity of the osseous vestibule. Between the osseous and 

 membranous portions remains a space traversed by anastomosing 

 connective-tissue trabeculae, and lined by endothelium, which also 

 forms an investing membrane around the trabeculae. These trabe- 

 culae pass on the one side into the periosteum lining the vestibule, 

 and on the other, into the wall of the utriculus and sacculus. The 

 cavity which they thus traverse represents a perilymphatic space. 

 (Compare Fig. 370, which shows analogous relations in the semi- 

 circular canals.) 



The wall of the utriculus, especially its inner portion, consists 

 of dense fibrous connective tissue, most highly developed in the 

 region of the macula acustica. In the immediate vicinity of the 



