236 



MAMMALIAN ANATOMY 



In Fig. 170 is represented the lateral aspect of that part of a longi- 

 tudinal vertical section which passes through the temporal bone. It 

 exhibits the true inner wall of the vestibule and part of the first whorl 

 of the cochlea. It should be compared with the drawing of the cast 

 of the labyrinth (Fig. 171). 



FIG. 171. 



Superior Ampulla. 



External Ampulla. 



Fenestra Oval is 



Cochlea. 



United Superior and Posterior 



Semicircular Canals. 

 "'External Semicircular Canal. 

 "'Posterior Amptilla. 

 Scala Vestibu/i. 

 --Fenestra Rotunda. 



METAL CAST OF THE LEFT BONY LABYRINTH. LATERAL ASPECT. 



(Enlarged Four Times.) 



The medial aspect of an oblique cranial section which passes 

 through the superior and posterior borders of the petrous (Fig. 172) 



FIG. 172. 



Head of Malleus. 



.JSctotympanic Book. 



Posterior Semicircular Canal. - - . -- 



Aquceductus Fallopii. 

 To Aqutzductus Vestibuli. 

 External Ampulla. 



Stapes in Fenestra Oi-alis. 

 Slit to Scala Tympani. - 



Posterior Ampulla. 



Porous Area. - 

 Foramen Singidare. 



Scala Tympani.- 

 To Aquceductus Cochlea. 



^External Auditory Meatus. 

 . Handle of Malleus. 



Scala Vestibuli. 



Spiral Cribriform Tract. 

 -Lamina Spiralis. 

 Scala Vestibuli. 



- - -Eustachian Groove. 



SECTION OF LEFT PETROUS THROUGH SUPERIOR AND POSTERIOR BORDERS. MEDIAL 



ASPECT. (Enlarged Four Times.) 



is similar to the section illustrated in Fig. 165, but it passes lateral 

 to the hiatus Fallopii and opens up more of the cochlea. 



A transverse vertical cranial section through the posterior edge of 



