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 1 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, 
z 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 
a coronoid process of the lower jaw. This 
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 Hyosna) 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 b 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. 
