140 





and in the fresh state is covered with cartilage. In front of the articular tubercle 

 is a small triangular area which assists in forming the infratemporal fossa; this 

 area is separated from the outer surface of the squama by a ridge which is continu- 

 ous behind with the anterior root of the zygomatic process, and in front, in the 

 articulated skull, with the infratemporal crest on the great wing of the sphenoid. 

 Between the posterior wall of the external acoustic meatus and the posterior root 

 of the zygomatic process is the area called the suprameatal triangle (Macewen), 

 or mastoid fossa, through which an instrument may be pushed into the tympanic 

 antrum. At the junction of the anterior root with the zygomatic process is a pro- 

 jection for the attachment of the temporomandibular ligament; and behind the 

 anterior root'is an oval depression, forming part of the mandibular fossa, for the 

 reception of the condyle of the mandible. The mandibular fossa (glenoid fossa) 



Parietal 

 notch 



Eminentia 

 arcuata 



Masloid foramen 



Aquceductus vestibuli 



Aquceductus cochlcce 



Internal acoustic meatus 

 FIG. 138. Left temporal bone. Inner surface. 



is bounded, in front, by the articular tubercle; behind, by the tympanic part of 

 the bone, which separates it from the external acoustic meatus; it is divided into 

 two parts by a narrow slit, the petrotympanic fissure (Glaserian fissure). The 

 anterior part, formed by the squama, is smooth, covered in the fresh state with 

 cartilage, and articulates with the condyle of the mandible. Behind this part 

 of the fossa is a small conical eminence; this is the representative of a prominent 

 tubercle which, in some mammals, descends behind the condyle of the mandible, 

 and prevents its backward displacement. The posterior part of the mandibular 

 fossa, formed by the tympanic part of the bone, is non-articular, and sometimes 

 lodges a portion of the parotid gland. The petrotympanic fissure leads into the 

 middle ear or tympanic cavity; it lodges the anterior process of the malleus, and 

 transmits the tympanic branch of the internal maxillary artery. The chorda 



