244 



MAMMALIAN ANATOMY 



FIG. 176. 



nial elements of the hyoid, the tympano-hyal and the stylo-hyal, are 

 coalesced and firmly fastened in a pit, thus forming the styloid pro- 

 cess of the bone. The inferior surface of the petrous presents, just 

 medial to the tympanic plate, a large circular foramen leading into 

 a canal which bends forward and inward and, traversing the petrous, 

 opens again at the apex. This is the canal through which the large 

 internal carotid artery enters the cranial cavity (Fig. 179). 



The remaining differences between the two temporals are princi- 

 pally differences in details. In the human bone the squamous is 

 flatter, and its inner surface (Fig. 176) is more deeply marked by the 



cerebral convolutions and by 

 grooves for the great meningeal 

 vessels. A large part of the 

 glenoid cavity (Fig. 177) is on 

 the inferior surface of the squa- 

 mous and a lesser part only on 

 the zygomatic process ; it is more 

 nearly circular in outline and 

 more deeply concave. It is 

 bounded in front by the anterior 

 root of the zygoma, or articular 

 eminence, the outer end of which 

 is sometimes called the pregle- 

 noid tubercle. A swelling at 

 the outer posterior part of the 

 cavity is called the postglenoid 

 tubercle, and one at the medial 

 end the entoglenoid tubercle. 

 In front of the o-lenoid cavitv 



INTERNAL VIEW OF THE TEMPORAL BONE OF 

 THE LEFT SIDE. 



1, squamous portion ; 2, posterior border of the mastoid 

 portion articulating with the occipital bone ; 3, petrous 

 portion; 4, bevelled edge, which overlaps the lower edge 

 of the parietal bone; 5, notch between the squamous and 

 the mastoid portion, articulating with the posterior in- 

 ferior angle of the parietal bone : 6, end of the zygomatic 

 process; 7, groove for the great meningeal vessels; 8, 

 mastoid process; 9, digastric fossa; 10, mastoid foramen 

 opening into the groove, 11, for the lateral sinus; 12, in- 

 ternal auditory meatus; 13, styloid process; 14, promi- 

 nence produced by the superior semicircular canal of the 

 labyrinth ; 15, tegnien ; 16, position of hiatus of the facial 

 canal; 17, cleft which communicates with the aquse- 

 ductus vestibuli; 18, termination of the carotid canal; 19, 

 Eustachian tube ; 20, groove of the superior petrosal sinus. 



is a smooth triangular area 



which forms part of the zygo- 

 matic fossa of the skull. 



The external auditory meatus (Fig. 175) is a funnel-shaped canal ; 

 the everted irregular edge of the tympanic plate which forms the lower 

 boundary of the meatus is called the auditory process. 



The mastoid process is very large, and is separated behind from 

 the rest of the mastoid portion by a deep groove, the digastric fossa, 

 for the digastric muscle (Fig. 177). At the upper end of this fossa 



