146 DIGESTION. 



In man, the articulation of the lower jaw with the tempo- 

 ral bone is such as to allow, to a considerable extent, of an 

 antero-posterior sliding movement and a lateral movement, in 

 addition to the ordinary movements of elevation and depres- 

 sion. The condyloid process is convex, with an ovoid surface, 

 the general direction of its long diameter being transverse and 

 slightly oblique from without inward and from before back- 

 ward. This process is received into a cavity of correspond- 

 ing shape in -the temporal bone, called the glenoid fossa, 

 which is bounded, anteriority, by a rounded eminence (erni- 

 nentia articularis), the uses of which will be more fully de- 

 scribed in connection with the movements of the jaw. 



Between the condyle of the lower jaw and the glenoid 

 fossa, is an oblong, inter-articular disk of fibre-cartilage. 

 This disk is thicker at the edges than in the centre. It is 

 pliable, and so situated that when the lower jaw is projected 

 forward, making the lower teeth project beyond the upper, it 

 is applied to the convex surface of the eminentia articularis 

 and presents a concave surface for articulation with the con- 

 dyle. One of the uses of this cartilage is to constantly present 

 a proper articulating surface upon the articular eminence, 

 and thus admit of the antero-posterior sliding movement of 

 the lower jaw. It is also important in the lateral movements 

 of the jaw, in which one of the condyles remains in the gle- 

 noid cavity, and the other is projected, so that the bone un- 

 dergoes a slight rotation. 



Muscles of Mastication. To the lower jaw are attached 

 certain muscles by which it is depressed, and others by 

 which it is elevated, projected forward and drawn backward, 

 and moved from side to side. The following are the princi- 

 pal muscles concerned in the production of these varied 

 movements : 



