MEMBRANA PROPRIA OF THE DUCTUS COCHLEARIS. 1 4o 



tion and the membrana basilaris, the sulcus spiralis externus 

 (S sp e). The two chief portions of the tympanal wall, already 

 named, the crista spiralis and the membrana basilaris, are best 

 separated from one another by the point of entrance of the 

 cochlear nerves into the cavity of the ductus cochlearis. The 



Fig. 323. Surface view of the lamina spiralis of Man in the second 

 turn, as seen from the vestibule, and magnified 30 diameters. From a 

 woman aged 28. The membrane of Reissner and the membrana tec- 

 toria have been removed. The zonular or girdle-like arrangement of 

 the several parts is very apparent. A, lamina spiralis ossea ; B, 

 lamina spiralis membranacea ; C, dark zone of the lamina spiralis 

 ossea (covered only by a thin peri osteal layer and the epithelium of 

 the vestibular scala ; D, crista spiralis, with a brighter appearance ; 6, 

 its projecting border, with the rows of auditory teeth ; a, line of attach- 

 ment of the membrane of Reissner ; a z, the part of the lamina 

 spiralis belonging to the ductus cochlearis (tympanal wall of the duct) ; 

 c, vas spirale faintly seen through the tympanal surface, accompanied 

 by spiral bands of connective tissue ; d, floor of the sulcus spiralis 

 internus, with fibres running radially on the tympanal surface 

 glimmering through e, lines in which lie the holes of emergence of 

 the nerve fibres ; /, organ of Corti ; g, external epithelium (/ and g 

 detached from the right half of the specimen). 



crista spiralis (R -/) rests upon the most external portion of 

 the lamina spiralis ossea, and is composed of two lips, the 

 labium vestibulare (fig. 325, c) (Henle), which terminates in a 

 sharp process (O), projecting into the ductus cochlearis and 



