THE EAR. 393 



the middle of the upper part of the cartilage is a small oval ojiening- 

 (av.), the ap. aquaedactus vestibuli : about midway between this 

 aperture and the jugular foramen is a second opening in the 

 cartilage (era.), the opening of the canalls rami anferioris {yesfihu- 

 laris) acustici : a little behind and above this is the opening of the 

 canalis rami posterioris [cocJilearis) acustici, situated in the exocci- 

 pital. The cartilage between the prootic and exoccipital in the 

 lower half of the interno-inferior surface rests on the parasphenoid. 



b. The position of the soft parts in the capsule. The large 

 outer^ rounded part of the cavity contains the saccule and cochlea 

 [fovea sacciili et cochleae) {fie). Above, the cavity is more irregular, 

 and contains the utricle and the si^ms tttriculi superior. In 

 front and externally, imbedded in a deep groove, are the anterior 

 and external ampidlae [fovea ampullae anterioris et amp. externae) ; 

 to these are attached the corresponding semicircular canals. The 

 anterior semicircular canal opens above and externally into the canal 

 of the sinus utriculi sujjerior ; the posterior passes into a groove for 

 the posterior ampulla [fovea ampullae ptosterioris), and opens above 

 and internally into the posterior semicircular canal. The external 

 semicircular canal courses in the processus sqnamosus prootici, the 

 posterior in the cartilage (Fig. 244 cj)) between the prootic and 

 exoccipital, and the anterior in the prootic. The upper and poste- 

 rior part of the anterior semicircular canal is imbedded in cartilag-e, 

 on which rests the parasphenoid. 



c. The perilymphatic space (Fig'. 245 I and II. The mem- 

 branous labyrinth does not occupy the whole space enclosed by the 

 hard parts but is surrounded by the perilymphatic, space, which 

 contains the perilymph. The periosteum and perichondrium form 

 the outer lining of the space, and are for the most part pig-mented. 



The perilymphatic space is widest in the lower part of the organ, 

 in the region of the fovea sacculi et cochleae, especially externally 

 and behind [per); in front it is much narrower [per^). A little 

 higher, in the region of the tegmentum vasculosum, the space is 

 wanting, as the membranous labyrinth is here attached to the 

 periosteum. 



Around the utricle and saccule the sjjace is comparatively wide ; 

 it is continued into the bony canals and ampullae. In the semi- 

 circular canals the space is wider on the concave side than on the 

 convex side, the membranous canals being placed eccentrically, as 

 are also the ampullae, though to a less extent. The periosteum and 



