78 ELEMENTS OF MAMMALIAN ANATOMY. 
ing the fibers is the endomysium, while that enveloping the 
fasciculus is the perimysium. A number of fasciculi bound 
together in a sheath, the epimysium, constitutes the entire 
muscle. The epimysium is merely a deflected portion of the 
sheath enveloping the fasciculus. It is visible to the naked 
eye as a thin shining sheath beneath the tougher fascia 
which covers the muscles and binds them together. 
According to function, muscles are spoken of as flexors, 
extensors, adductors, abductors, rotators, clevators, depres- 
sors, and sphincters. A flexor muscle is one which by its 
contraction bends a limb or any portion of it. An extensor 
muscle is the antagonist of a flexor and serves to bring the 
two long bones into line. An abductor muscle is the one 
inserted on a long bone, which it draws laterad from the 
axis of the limb or the sagittal plane of the body. An 
abductor muscle is the antagonist of an abductor. The 
pectoral muscles are abductors of the forelimb. A rotator 
muscle is one which produces more or less of a rotatory 
motion in the bone upon which it is inserted. A rotator 
muscle is exemplified in the obturators, which arise on the 
innominate bone and are inserted in the digital fossa of the 
femur. An elevator nuscle is represented by the temporal, 
extending from the temporal bone to the mandible, which 
it elevates. A depressor muscle is the antagonist of an 
elevator. The digastric is a depressor of the mandible. A 
sphincter muscle is one surrounding an orifice which it 
closes by contraction. The orbicularis oris in the lips is an 
example. : 
Muscles are named according to their function, shape, 
or part to which they are attached. Thus the sterno- 
mastoid muscle arises on the sternum and is inserted on the 
mastoid process of the skull. The latissimus dorsi is so 
named because it is a very broad muscle (Fig. 47) and 
occupies the dorsal part of the cat’s body. The extensor 
