THE SKULL THE CRANIUM 



247 



FIG. 178. 



14 



LONGITUDINAL SECTION OF TEMPORAL BONE, 

 THROUGH THE TYMPANUM. 



vessels and nerves through an opening behind into the aqu^ductus 

 Fallopii. The pyramid corresponds to the bony bridge and the ad- 

 joining petrous wall in the 

 tympanum of the cat. Close 

 to the groove for the attach- 

 ment of the tympanic mem- 

 brane is the opening for the 

 chorda tympani nerve. A 

 fossa on the posterior wall 

 behind and above 'the fenestra 

 rotunda and beneath the pyra- 

 mid is sometimes termed the 

 tympanic sinus ; in the cat it 

 is represented by the lower 



part of the Slit between the 1. external auditory meatus; 2, auricular fissure; 3, open- 



ing of canal for Arnold's nerve ; 4, tympanic sinus ; 5, tym- 



petrOUS and the bl*id'e. panic groove; 6, fenestra rotunda; 7, tympanic opening of 



the tympanic canaliculus; 8, promontory; 9, tympanic end 



It is important tO note that of Eustachian canal; 10, small foramina; 11, Eustachian 



canal ; 12, septum ; 13, canal for the tensor tympani muscle ; 



the fossa for the tenSOr tym- 14, processus cochleariformis; 16, fenestra ovalis; 17, swell- 

 ing due to aquseductus Fallopii ; 18, swelling due to external 



paili mUSCle is not a deep Cll'- semicircular canal; 19, antrum of tympanum; 20, pyramid; 



21, posterior sinus. 



cular depression on the infe- 

 rior surface of the petrous, but a long tube which extends forward 



and inward above the Eusta- 

 chian tube, from which it is 

 separated by a scroll of bone, 

 the processus cochleariformis, 

 represented in the cat by the 

 inverted superior part of the 

 ectotympanic. 



The tympanic canaliculus, 

 beginning in the inferior sur- 

 face of the petrous, opens at the 

 bottom of the tympanum and is 



1, apex of the petrous; 2, carotid canal; 3, hiatus Fal- COlltilllied Upward aS a grOOVC 



lopii; 4, 5, aquceductus Fallopii; 6, external semicircular /TT*' 



canal; 7, mastoid cells; 8, pyramid; 9, sinus of pyramid; aCrOSS the prOlllOlltory (f Ig. 



10, carotico-tyrnpanic canaliculi; 11, bristle showing course n T '1 



of Jacobson's nerve and its continuation, the small super- 1/9). i.t transmits til 6 tVlll- 



ficial petrosal nerve ; 12, groove on the promontory for the . . . , . ,, 



tympanic plexus; 13, feuestra rotunda; 14, promontory; paillC bl'aiicll (JaCODSOnS) 01 



15, a bridge of bone. . , 



the ninth cranial nerve, a 

 branch of which runs upward through a canal in the petrous near 



FIG. 170. 



15 



.-6 



1.. 



SECTION OF TEMPORAL BONE THROUGH TYM- 

 PANUM, CAROTID CANAL, AND AQUJEDUCTUS 

 FALLOPII. 



