THE BONES OF THE HEAD 



71 



On the outer surface of the zygoma, above the place where the 

 anterior root becomes continuous with its lower border, there is 

 a projection, called the preglenoid tubercle, which gives attach- 

 ment to the external lateral ligament of the temporo-maxillary 

 articulation. 



Behind the anterior root is the glenoid fossa, which extends 

 on to the tympanic plate. It is elongated from before backwards 

 and inwards, and is divided mto t\vo parts by the fissure of Glaser. 

 The anterior part, which belongs to the squamo-z>'gomatic portion 



^ Sqoamoas Portion 



Groove for 

 Mid. Temp. Artery ^ 



Suprameatal Spine^ 

 and Triangle 



Supramastoid Crest ^ 

 ?arietal Notch ^ 



Mastoid 



Mastoid Portion 



Mastoid Process' 



"External Auditory Meatus' 



Ext. .Aud. Process 



Zygqna 



I*reglenoid Tuberck 



^ Ant. Root of Zygoma 

 (Eminent, .\rtic.} 



Ant. Part of Glenoid Fos.«a 



Fissure of Glaser 



Post. Part of Glenoid Fossa 

 (Tympanic Plate) 



Vaginal Process ■ ' 



Styloid Process 



Fig. 48. — The Right Temporal Bone (External View). 



of the bone, is covered by cartilage, and is triangular, with the apex 

 at the preglenoid tubercle and the base at the Glaserian fissure. It 

 is deeply concave, and is boimded anteriorly by the eminentia 

 articularis, externally by the commencement of the posterior root 

 of the zygoma, and posteriorly from without inwards by the post- 

 glenoid process and Glaserian fissure. 1 1 articulates \^ith the condyle 

 of the inferior maxilla when the mouth is closed, an interarticular 

 fibro-cartilage inter\'ening ; but, when the mouth is open, the condyle 

 with the fibro-cartilage moves forwards on to the eminentia articu- 

 laris. The posterior part of the glenoid fossa is situated behind the 



