88 ELEMENTS OF MAMMALIAN ANATOMY 



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 Jlcxors, extensors, adductors, abductors, rotators, 

 elevators, depressors and sphincters. K flexor muscle is one which 

 by its contraction bends a limb or any portion of it. An exten- 

 sor 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 adductor 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 contrac- 

 tion. 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 sternomastoid 

 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. 48) and occupies the dorsal part 

 of the cat's body. The extensor communis digitorum muscle 

 signifies by its name that it is the common extensor of the digits. 



DISSECTION OF THE MUSCLES 



Since the other systems are of more importance from the 

 standpoint of comparative anatomy and physiology than the 

 muscular, only the more important muscles will be described. 

 Great care should be exercised in removing the skin of the 



