468 BONES AND MUSCLES OF THE FACE. 



articulated with, the temporal bones by a condyle or projecting 

 head with which each of these extremities is furnished ; and 

 this head is received into what is called the glenoid l cavity 

 on the under side of the temporal bone. In front of the 

 condyle is another projection, or process, termed the coronoid 

 (a, fig. 92), which serves for the attachment of one of the 

 principal muscles that raise the jaw. These muscles are all 

 attached near the angle of the jaw (or the point at which it 

 bends upwards), and they consequently act at a small distance 

 from its fulcrum, whilst the resistance is applied at the 

 furthest point ( 180). We are continually reminded of the 

 loss of mechanical power which results -from this, by our in- 

 ability to exercise the same force with our front teeth that we 

 can employ with the back. Thus, when we wish to crack 

 a nut, or to crush any hard substance between the teeth,, we 

 almost instinctively carry it to the back of the jaws, so as to 

 place it nearer the joint, where it may receive more of the 

 power of the muscle. 



624. The general arrangement of the chief muscles of the 

 face is seen in fig. 222. The largest is the temporal muscle, t, 

 the fibres of which arise from an extensive 

 surface of the parietal and temporal bones, 

 and then converge or approach each other, 

 passing under the bony arch or zygoma, z 

 (which is partly formed by a process from 

 the temporal bone, and partly by the malar 

 or cheek bone), to be attached to the 

 j m c a coronoid process of the lower jaw. This 

 Fig. 222. muscle is of extraordinary power in those 



beasts of prey which lift and drag heavy carcases in their 

 jaws; and in those which (like the Hyaena) obtain their 

 support by crushing the bones that others have left. It is 

 assisted by the masseter muscle m, which passes from the 

 zygomatic arch and cheek-bone to the angle of the lower jaw, 

 and also by other muscles. Besides these, the figure shows 

 the ring-like muscle or sphincter o, which surrounds the 

 opening of the eye, and serves by its contraction to close the 

 lids ; and also the similar muscle 6 b, which surrounds the 



1 The term condyle is applied to most of the projecting surfaces of 

 articulation, in different parts of the body; and the term glenoid to 

 the cavities into which these are received. 



