THE CAT 257 



Study first the superficial muscles of the side of the body. Re- 

 move the fat which may overlay any of these muscles. Note the 

 broad, white membrane which covers the back in the abdominal 

 region ; this is the lumbodorsal fascia. Note also the narrow, white, 

 midventral line ; this is the linea alba. 



On the side of the trunk between the forelegs and hind legs two 

 large muscles occupy almost the whole space, the external oblique 

 and the latissimus dorsi. The former is a thin plate which covers 

 the lateral and ventral portions of the abdomen. It arises from 

 the last nine or ten ribs and the lumbodorsal fascia and extends 

 ventroposteriorly to the midventral portion of the abdomen. The 

 latissimus dorsi is a broad muscle which arises from the neural 

 processes of the nine posterior thoracic and the six anterior lumbar 

 vertebrae and passes over the dorsal portion of the anterior end of 

 the external oblique to the forearm and shoulder, where it is in- 

 serted in the medial surface of the humerus. It draws the arm back. 



Immediately anterior to this muscle, on the dorsal side of the 

 trunk, are the trapezius muscles. The posterior trapezius, or spi- 

 notrapezius, arises from the neural processes of the thoracic 

 vertebrae and passes to the spine of the scapula. The middle 

 trapezius, or acromiotrapezius, lies in front of the last-named 

 muscle and directly above the scapula. It arises along the mid- 

 dorsal line of the neck and shoulder and passes to the spine of the 

 scapula. The anterior trapezius, or clavotrapezius, arises from 

 the posterior surface of the skull and the mid-dorsal line of the 

 neck and extends downward along the sides of the neck to the 

 clavicle, where it is continuous with the clavobrachial, a muscle 

 which extends ventrally to the ulna. 



Ventral to the middle trapezius is the spinodeltoid muscle, which 

 extends from the spine of the scapula to the anterior side of the 

 humerus. Between the two last-named muscles and the anterior 

 trapezius are the acromiodeltoid and the levator scapulae, the latter 

 being dorsal to the former. 



In front of the anterior trapezius, on the side of the neck, is the 

 sternomastoid muscle, whose function is to turn and depress 

 the head; it extends from the skull back of the external ear to 

 the breastbone. 



