258 VERTEBRATE ZOOLOGY 



On the side of the head are two prominent muscles, the mas- 

 seter and the temporal, whose function is to close the lower jaw. 

 The former lies below and back of the eye ; the latter is a large 

 fan-shaped muscle, which covers the side and top of the head, back 

 of and above the eye, and extends to the lower jaw. 



On the proximal division of the foreleg are seen two large 

 muscles, the lateral and the intermediate portions of the triceps ; 

 they are inserted by a broad tendon in the olecranon process of 

 the ulna. The intermediate portion extends from the scapula and 

 forms the hinder border of the upper arm; the lateral portion 

 extends from the proximal end of the humerus. 



On the proximal division (the thigh) of the hind leg are seen 

 the sartorius muscle, which forms its anterior border, and the 

 biceps femoris, a large muscle which forms its middle and hinder 

 portion. Between them is the membranous fascia lata. 



Exercise 46. Draw the lateral aspect of the animal and place in it 

 the outlines of these muscles, showing the direction of their fibers. 

 Carefully label all. 



Study the muscles of the ventral aspect of the trunk and legs. 

 Covering the abdomen are the paired external oblique muscles, 

 which have already been described. In the region of the breast 

 are the pectoral muscles. These constitute a group of four large 

 muscles, more or less connected with one another, which extend 

 from the sternum to the humerus and pull the forelegs backward 

 and medially. In front of the anterior pectoral is the clavobra- 

 chial, which we have already seen; its dorsal continuation, the 

 clavotrapezius, appears on the side of the neck. Medial to the 

 last-named muscle is the sternomastoid. 



On the upper arm the posterior border is formed by the inter- 

 mediate portion of the triceps ; the ventral portion is formed by the 

 biceps brachii, which extends from the scapula to the humerus. 



On the hind leg two prominent muscles appear on the inner 

 side of the thigh : the sartorius, which forms its anterior portion, 

 and the gracilis, which forms its posterior portion. 



Exercise 47. Draw the ventral aspect of the trunk, and place in it 

 outlines of these muscles showing the direction of their fibers. 



