94 ELEMENTS OF MAMMALIAN ANATOMY. 



clastic sheath, the sarcolemma. A number of fibers 

 bound together by a loose connective tissue, and the 

 whole enveloped by an extension of the same, is a fascic- 

 ulus. The tissue connecting the fibers is the endomy- 

 sium, while that enveloping the fasciculus is the peri- 

 mysium. 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 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 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 obtu- 

 rators, which arise on tfie 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 ex- 

 ample. 



Muscles are named according to their function, shape, 



