THE INTERNAL EAR. 



487 



membrane, extends peripherally (externally), and ends in two 

 sharp ridges, of which the shorter, the labium vcstibulare, projects 

 into the inner space of the cochlear duct and continues into the 

 tectorial membrane ; while the other and longer, the labium tym- 

 panicum, becomes attached to the wall of the scala tympani and 

 continues into the basilar membrane. Between the two ridges is a 

 sulcus, the sulcus spiralis interims. (Fig- 373-) The limbus spiralis 



Fig. 373. Section through one of the turns of the osseous and membranous coch- 

 lear ducts of the cochlea of a guinea-pig ; X 9 : ?> Scala vestibuli ; m, labium vestibu- 

 lare of the limbus ; , sulcus spiralis internus ; o, nerve-fibers lying in the lamina spi- 

 ralis ; /, ganglion cells ; q, blood-vessels ; a, bone ; b, Reissner's membrane ; DC, ductus, 

 cochlearis ; d, Corti's membrane;/", prominentia spiralis; g, organ of Cord; h, liga- 

 mentum spirale ; i, crista basilaris ; k, scala tympani. 



is a connective-tissue formation in the region of the cochlear duct 

 connected with the periosteum of the osseous spiral lamina and 

 extending from the point of attachment of Reissner's membrane 

 to the labium tympanicum. The tissue of the limbus spiralis is 

 dense and richly cellular, and simulates in its structure the sub- 

 stantia propria of the cornea. A casual view would seem to disclose 



