1058 



ORGANS OF SPECIAL SENSE 



oval, whitish, thickened area, macula acustica utriculi, marks the terminal distribu- 

 tion of the nerve, and posteriorly the utricle is joined by the orifices of the semicircular 

 canals. The saccule ,s a flattened, oval sac, smaller than the utricle, and situated in 

 the anterior and inferior part of the vestibule. It is bound to the spherical recess (fovea 



FIG. 752. THE OSSEOUS LABYRINTH OF THE RIGHT SIDE. 

 (Modified from Soemmerring. Enlarged.) 



Superior semicircular canal 



Posterior semicircular canal 



Lateral se*micircular canal 



Vestibule and feneatra ovalis 



Ampulla 

 Ampulla 



Second turn of cochlea 

 Cupula of cochlea 





Ampulla 



Fenestra cochlearis 

 Commencement of first turn of the cochlea 



hemispheerica) by connective tissue and by the saccular division of the acoustic nerve, 

 filaments of which extend from the middle macula cribrosa to the anterior and medial 

 wall of the saccule, to be distributed over a thickened area, macula acustica sac- 



FIG. 753. INTERIOR OF THE OSSEOUS LABYRINTH OF THE LEFT SIDE. 

 (Modified from Soemmerring. Enlarged.) 



Superior semicircular canal 



ELLIPTIC RECESS (FOVEA 

 HEMIELUPTICA) 



SUPERFICIAL RECESS (FOVEA 

 H EM ISPH ERICA) 



Lamina spiral! a 

 Bcala tympani of cochlea 



Posterior semicircular canal 



Lateral semicircular canal 



Opening common to superior and 



posterior semicircular canal 

 Internal aperture of vestibular 

 aquaeduct 



Internal aperture of cochlear 

 caii all culua 



culi. Anteriorly and inferiorly the saccule gradually passes into a short canal, the 

 ductus reuniens, which connects it with the cochlear duct, and posteriorly the very 

 small endolymphatic duct is attached. This extends through the aquseductus ves- 



FIG. 754. INTERIOR OF THE OSSEOUS COCHLEA. (Enlarged.) 



Scala vestibuli 



Scala tympani 



Lamina spirali3 



tibuli to the posterior surface of the petrous portion of the temporal bone, where it 

 ends in a dilated blind pouch, the endolymphatic sac, situated just beneath the dura. 

 Just beyond the saccule the endolymphatic duct is joined at an acute angle by a short 

 canal of minute calibre, the utriculo-saccular duct, which opens into the utricle 



