7 8 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, elevators, 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 

 aQductor muscle is the antagonist of an abductor. The 

 pectoral muscles are adductors 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 muscle 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. 4^) and 

 occupies the dorsal part of the cat's body. The extensor 



