PHYSIOLOGICAL ANATOMY OF THE INTERNAL EAR. 8 45 



2. The scala vestibuli. This is formed by the periosteum lining the corresponding 

 portion of the bony cochlea and the upper surface of the bony septum and is bounded 

 externally by the membrane of Reissner. 



3. The true membranous cochlea. This is the spiral triangular canal, bounded ex- 

 ternally by the periosteum of the corresponding portion of the wall of the cochlea, 



Fio. 266. Sectionof the first tivm of the spiral canal of a cat newly-born. Section of the cochlea of a human 

 fmtw at the fourth month. From a photograph, and somewhat reduced. (Rfidinger.) 



Upper figure : 1, 2, 6, lamina spiralis ; 2, lower plate ; 8, 4, 6, 5, nervus cochlearis ; 7, membrane <>t mem- 



brana tectoria; 9, epithelium ; 10, 11, pillars of Corti; 12, inner hair-cells; 13, outer hair-cells ; 14. Hi. mombrana 

 basilaris; 15, epithelium in the sulcus spiralis; 17, 18, 19, ligainentum spirale; 20, spiral canal below the niembrana 

 basilaris. 



Lower figure: S T, S T, 5, 5, 7, 7, 8, 8, scala tympani ; 8 V, 8 V, 9, 9, scala vestibuli; 1, base of the cochloa ; 2, apex ; 

 8, 4, central column; 10, 10, 10, 10, ductus cochlearis; 11, branches of the nervns cochlearis: ]_'. l-J. I-. 1 , sj.ir.il 

 ganglion; 13, 14, limbus laminse spiralis; 15, membrane of Reissner; 16, epithelium : 17. outer h:iir-o-lls; H, 

 epithelium of the membrana basilaris; 10, nervous filaments; 20, union of the nicml.rann basilaris with th> 

 ligamentum spirale ; 21, epithelium of the peripheral wall of the ductus cochlearis; 22, 23, membrana tectoria ; 

 24, spiral canal below the membrana basilaris. 



internally, by the membrane of Reissner, and, on the other side, by the membrana basi- 

 laris. 1 What we thus call the membranous cochlea is divided by the limbus liiminro spi- 

 ralis and the membrana tectoria into two portions ; a triangular canal above, which is the 



i Some anatomists include this canal in the scala vestibuli. For the sake of clearness, we describe it by itself, as a 

 distinct canal. 



