DISSECTION OF THE ANTERIOR LIMB. 15 



resting in the twist formed by the tendon of the latissimns dorsi 

 muscle. 



Action. — It is a flexor and an inward-rotator of the shoulder. 



The Scapulo-Ulnaris (Plate 5). This is a thin, flat muscle which 

 rests on the inner surface of the triceps, and is provided, in front and 

 above, with a thin, transparent tendon. It arises from the posterior 

 border of the scapula, and is inserted into the posterior border of the 

 olecranon and the fascia of the fore-arm. At its lower extremity the 

 muscle covers the ulnar vessels and nerves. 



Action. — To extend the elbow-joint, and tense the fascia of the 

 fore-arm. 



The Triceps Extensor Cubiti. This is an immense muscular mass 

 which, with the preceding, fills up the angle formed behind the 

 shoulder-joint. It has three divisions or heads, which may be 

 distinguished as the caput magnum, the caput medium, and the 

 caput parvum. 



The Caput Magnum, or large head (Plate 5), forms a great mass 

 which is seen on both the outside and the inside of the limb. It arises 

 from the dorsal angle and glenoid (posterior) border of the scapula ; 

 and it is inserted into the olecranon, there being a synovial bursa 

 between the summit of that eminence and the tendon. 



The Caput Parvum, or small head (Plate 5), is, when compared with 

 the preceding, a very small muscle. It arises from the shaft of the 

 humerus below and behind the internal tubercle, and it is inserted into 

 the olecranon. 



The Caput Medium, which is not now visible, will be dissected with 

 the outside of the shoulder. 



Action of the triceps. It is an extensor of the elbow-joint, and acts 

 as a lever of the first order, the joint, which represents the fulcrum, 

 being between the power and the weight. The large head is also a 

 flexor of the shoulder. 



The Subscapularis (Plates 5 and 6). This muscle is lodged in the 

 fossa of the same name on the ventral surface of the scapula, and it 

 arises from the whole extent of that fossa. It is inserted into the inner 

 tuberosity of the humerus, a small synovial bursa being interposed be- 

 tween the tendon and the bone. The tendon is crossed by the origin 

 of the coraco-humeralis, and another small bursa is here interposed 

 between the tendons. Above its insertion it is closely related to the 

 capsular ligament of the joint. The muscle is partly united in front 

 with the supraspinatus, and behind with the teres major. 



Action. — It is an adductor of the shoulder. 



The Coraco-humeralis (or coraco-brachialis) (Plates 5 and 6). This, 

 which is rather a small muscle, arises from a small tubercle on the 

 inner side of the coracoid process of the scapula. It has two insertions, 



