COMPARATIVE ANATOMY OF THE MUSCULAR SYSTEM 145 



g) Deltoids. There are three deltoids in the rabbit, of which one, the 

 clavodeltoid, has already been considered. The second deltoid is a small triangu- 

 lar muscle lateral to the clavodeltoid. Origin, acromion process; insertion, 

 humerus ; action, raises the humerus. The third deltoid is lateral to the second 

 and is a longer muscle. It passes under the long metacromion process and 

 takes its origin from the fascia of the muscle which fills the infraspinous fossa. 

 Insertion and action like the preceding. 



h) Infraspinatus. The muscle partly covered by the third deltoid which is 

 attached to its surface. The deltoid may be removed to see it. Origin, infra- 

 spinous fossa and spine; insertion and action like the sup rasp inatus. 



i) Teres major. The stout muscle along the axillary border of the scapula 

 behind the preceding. Origin, dorsal half of the axillary border of the scapula; 

 insertion, on the humerus in common with the latissimus dorsi; action, draws 

 humerus against body and rotates it. 



j) Teres minor. Separate the teres major well from the infraspinatus and 

 look in between them. On the inner surface of the latter will be found a small 

 but stout muscle. Origin, ventral half of the axillary border of the scapula; 

 insertion, greater tuberosity of the humerus ; action, like the preceding. 



k) Rhomboideus capitis (levator scapulae minor of B). Cut through the 

 rhomboideus. A slender bandlike muscle lies in contact with the inner surface 

 of the rhomboideus and passes along the external surface of the splenius to be 

 connected with the skull. Origin, side of the skull above the tympanic bulla; 

 insertion, posterior end of the vertebral border on the medial side; action, draws 

 scapula craniad and rotates it. 



I) Subscapulars. Lift the scapula. A large muscle, the subscapularis, com- 

 pletely covers the medial or inner surface of the scapula, its fibers disposed 

 in several directions. The muscle has a shining fascia; its posterior end is more 

 or less continuous with teres major. Origin, medial surface of the scapula; 

 insertion, lesser tuberosity of the humerus; action, pulls the humerus toward 

 the median ventral line. 



m) Serratus centralis {anterior). On raising with the finger the vertebral 

 border of the scapula a large fan-shaped muscle will be seen extending anteriorly 

 and posteriorly from the scapula to the walls of the thorax. This is the serratus 

 ventralis ; it is readily divisible into anterior and posterior portions. The anterior 

 or cervical portion originates on the transverse processes of the cervical vertebrae 

 by separate slips and on the first two ribs. The posterior or thoracic portion takes 

 its origin by seven slips from the ribs. Insertion, vertebral border of the scapula 

 above the subscapularis; action, draws scapula forward, backward, or against 



the body. 



n) Scalenes. The scalenes are several long flat muscles extending from 

 the transverse processes of the cervical vertebrae to the ribs. They will be 

 seen by lifting up the scapula and looking on the ventral side of the origin of the 



