ANATOMY OF THE INTERNAL EAR. 



217 



nous cochlea is divided by the limbus laminse spiralis and the 

 membrana tectoria into two portions; a triangular canal 

 above, which is the larger, and a quadrilateral canal below, 

 between the limbus and membrana tectoria and the mem- 

 brana basilaris. The quadrilateral canal contains the organ 

 of Corti and various structures of a very complicated char- 

 acter. The relations of these divisions of the cochlea, a 

 knowledge of which is essential to the comprehension of the 

 physiological anatomy of this portion of the auditory appara- 

 tus, are shown in Fig. 15, with the exception of the quadri- 

 lateral canal, which will be shown in another figure. 



FIG. 16. 



^^t - 



1. scala tympani ; 2, scala vestibuli; 8, triangular canal; 4, quadrilateral canal, catted 

 the canal of Corti ; 5, 5, spiral ligament ; 6, middle, or angular portion of the spiral ligament 

 giving attachment to the membrana basilaris; 7, portion of the spiral ligament giving at- 

 tachment to the membrana tectoria, or membrane of Corti ; 8, external spiral groove ; 9, 



" anterior extremity of the spiral ligament, giving attachment to the membrane of Reissner ; 



10, membrane of Reissner ; 10', vascular band, the outer boundary of the triangular canal; 



11. membrane of Corti; 12, membrana basilaris; 13, spiral vessel below the membrana 

 basilaris; 14, sulcus spiralis; 15, anterior portion of the band marked by furrows; 16, pos- 

 terior portion : 17, anterior margin ; 18, posterior margin : 19, the two pillars of the organ 

 of Corti ; 20. branch of the cochlear nerve ; 21. spiral ganglion ; 22. continuation of the nerve ; 

 23, one of the orifices by which the nerve passes to the organ of Corti ; 24. 24, bony tissue 

 of the cochlea; 25, 25. periosteum. (SAPPEY, Trait* (Fanatomie, Paris, 1871, tome iii., p. 

 845.) The parts which have been described In the text are indicated by italics. 



