THE EAR 



1549 



ligament. The inner wall presents anteriorly a depression called 

 the fovea spherica, which corresponds to the lamina cribrosa at 

 the deep end of the meatus auditorius internus. It is pierced by 

 apertures for the passage of filaments of the auditory nerve to the 

 saccule. Behind and above the fovea spherica there is a ridge, 

 called the crista vestibuli, which lies obliquely. Posteriorly it 

 bifurcates, and between its two divisions there is a small depression. 



Aqueduct of Fallopius 

 Cupola of Cochlea ^ ; 



Petrous part of Tem- 

 fxjral Bone 



Superior Semicircular Canal 

 Fenestra Ovalis 



External Semicircular 

 Canal 



Posterior Semicircular 

 Canal 



Vestibule 



^^_^. Fenestra Rotunda 



Superior Semicircular Canal 



Inner Wall of Canal ' 

 of Cochlea 



Helicotrema' 



Lamina Spiralis 



Crus Commune of Sup. and 



Post. Semicircular 



Canals 



Posterior Semicircular 

 Canal 



External Semicircular 

 Canal 

 ^- Fovea Elliptica 



Crista Vestibuli 

 ^ Fovea Spherica 



1 Orifice of Aqueductus Vestibuli 

 Recessus Cochlearis 

 Fenestra Rotunda 

 Scala Vestibuli 



Scala Tympan 



Fig. 649. — The Osseous Labyrinth of the Left Side (External View). 

 A, Entire ; B, Opened (Hirschfeld and Leveille. B, IModified). 



called the recessus cochlearis, which presents a few openings for 

 the passage of nerve filaments to the canalis cochleae. Anteriorly 

 it becomes some\vhat triangular, and forms the pyramid, which is 

 pierced by foramina for the passage of nerves to the utricle. 



The roof of the vestibule, behind and above the crista vestibuli, 

 presents an oval depression, called the fovea elliptica, which en- 

 croaches on the inner wall and lodges the recessus utriculi. It is 

 pierced by foramina for the passage of the nerves to the ampullae 



