246 



MAMMALIAN ANATOMY 



FIG. 177. 



carotid canal by a transverse crest which is pierced at its inner end by 

 a foramen, the tympanic canaliculus, which transmits the tympanic 

 branch (Jacobson's) of the ninth cranial nerve. Medial to this opening- 

 is the petrous fossula, in which is the opening of the aquseductus 



cochleae. At this point the margin of the bone 

 is grooved for the passage of the ninth, tenth, 

 and eleventh cranial nerves. In front of the 

 petrous fossula the inner margin of the surface 

 exhibits a groove for the inferior petrosal sinus. 

 Lateral to the groove is a rough space which artic- 

 ulates with the basilar plate of the occipital. The 

 region of the surface near the apex under the 

 carotid canal affords attachment to the pharynx. 

 The posterior wall of the carotid canal is pierced 

 by two small canals, the carotico-tympanic cana- 

 liculi, for tympanic nerves from the carotid plexus 

 (Fig. 179). 



In the notch, in front, between the petrous and 



INFERIOR VIEW OF THE 

 LEFT TEMPORAL BONE. 



portion; 2, mas- 



toid portion; 3, petrous por- 



tion; 4, border articulating the SQiiamous is the anterior end of the Glaserian 



with the great wing of the 



sphenoid bone; 5, zygoinatic fisSlire. A Small Cl'CSt of the petl'OUS appears 



process ; 6. glenoid fossa ; 7, 



articular eminence; s, Gia- between the squaiiious and the tympanic and 



serian fissure; 9, auditory 



meatus; 10, mastoid process; bounds internally the canal of Huguier. On 



11, digastric fossa; 12, styloid 



process; is, styio-mastoid fora- th e medial side of this crest are the Eustacliian 



men; 1-t, jugular fossa; 15, pit 



which communicates with the opening below and the canal for the tensor tym- 



aquaeductus cochleae ; 16, posi- 



tion between which and the paili lllUSCle above. 



occipital bone the ninth, 



tenth, and eleventh cerebral The llUlliail tympailUlll is USUallj divided illto 



nerves escape from the cavity 



of the cranium; 17, articular thl'66 parts : (a) the atrium, 1 tllG pOrtlOll wllidl 



process; 18, vaginal process; 



19, 20, entrance and exit of Jg visible tlirOUgll the external auditory HlGRtUS ; 



the carotid canal; 21, Eusta- 



chian tube; 22, mastoid fora- ($) the attic, the Superior portion, which COlltaillS 



men. 



the heads of the malleus and incus ; and (c) the 

 antrum, 2 an irregular space in the cancellous tissue of the petrous, 

 behind the attic, with which it is in communication (Fig. 178). The 

 atrium differs from the corresponding region in the tympanum of the 

 cat in the following points : On the posterior wall, just behind the 

 fenestra rotunda is a small pyramid, the apex of which is pierced by 

 a foramen for the tendon of the stapedius muscle. The interior of 

 the pyramid is hollow, and contains the muscle, which is supplied with 



1 The fore-court or hall. 2 A cave. 





