232 



MAMMALIAN ANATOMY 



upper wall of the vestibule will be removed, exposing the outer wall 

 with the fenestra ovalis ; the slit leading clown into the scala tympani ; 

 the floor formed of the lamina spiralis ; the superior ampulla above ; the 

 external ampulla above and behind ; the posterior ampulla below and 



FIG. 165. 



Superior Ampulla. . . 



External Ampulla, 



Fenestra Ovalis. 



External Semicircular Canal 



Posterior Ampulla. 



Foramen Singulare. 



Scala Tympani 



Aquseductus Cochlese. 



. .Aquseductus Fallopii. 

 Fossa for TENSOR TYMPANI. 



Superior Cribriform Spot. 



Lamina Spiralis. 

 - ^Hiatus Fallopii. 



Middle Cribriform Spot. 



Spiral Cribriform Tract. 

 Scala Vestibuli. 



LEFT PETROUS. MEDIAL ASPECT. (POSTERIOR SURFACE REMOVED.) 



(Enlarged Four Times.) 



behind, with the non-ampullar end of the external canal grooving its 

 wall. The common opening of the non-ampullar ends of the superior 

 and posterior canals has been destroyed. 



If the student have sufficient material, he should supplement these 

 observations by others made on a series of sections through the internal 



ear. 



FIG. 166. 



Fossa for TENSOR TYMPAN 



Fovea Hemi-elliptica, 



Fovea Hemisphserica, 



Fenestra Ovalis 



Slit to Scala Tympani 



Fenestra Rotunda 



..-, Aquieductus Fallopii. 



To Posterior and Superior Semi- 

 circular Canals. 

 Anterior-Medial Wall of 

 Vestibule. 



Posterior Ampulla. 



TRANSVERSE SECTION OF LEFT PETROUS. POSTERIOR ASPECT. 



(Enlarged Four Times.) 



The first section may be made across the petrous from above ob- 

 liquely downward and backward, at the upper part cutting the posterior 

 part of the tensor tympani fossa on the inferior surface and passing 

 just posterior to the fenestra ovalis and the fenestra rotunda. The 



