BONES OF THE CRANIUM. 185 



ion. Its external surface is 

 flat; forms a portion of the 

 temporal fossa, and gives at- 

 tachment to the temporal 

 muscle. Its internal sur- 

 face has depressions for the 

 convolutions of the brain, 

 and a groove for the poste- 

 rior branch of the middle 

 meningeal artery. 



It is bounded above by a 

 somewhat semicircular edge, 

 which overlaps the parietal bone and below by a long and 

 curved process, with its convexity outwards, called the zygo- 

 ma, or zygomatic process. This process is horizontal, and 

 arises by two roots the one runs transversely, is covered by 

 cartilage, and forms the anterior boundary of the glenoid 

 cavity the other passes horizontally backwards, forming 

 the outer boundary of the glenoid cavity, and is contin- 

 ued on and lost in the upper part of the mastoid process. 

 This posterior root gives off a middle branch, which passes 

 into the glenoid fissure, and partially forms the posterior 

 wall of the glenoid cavity. At the junction of the hori- 

 zontal and transverse roots there is seen a small tubercle, 

 giving attachment to the external lateral ligament of the 

 lower jaw the anterior extremity of the zygoma is serra- 

 ted and rests on the malar bone. Behind the transverse 

 root is the glenoid cavity, which is divided by a fissure 

 called the Glasserian that portion of the glenoid cavity 

 in front of this fissure is the proper articulating surface of 

 the lower jaw, while that behind the fissure is occupied by 

 a portion of the parotid gland the fissure has attached to 



FIG. 40 represents external surface of left Temporal Bone, a Squamous 

 portion. & Mastoid portion, c Extremity of petrous portion, d Zygomatic 

 process, e Tubercle in front of articular surface for condyle of lower jaw. 

 / Temporal ridge, posterior portion, g Glenoid fissure, h Mastoid foramen. 

 i Meatus auditorius externus. j Digastric fossa, k Styloid process. I Va- 

 ginal process, m Glenoid foramen, n Groove for the Eustachian tube. 



