DISSECTION OF THE ANTERIOR LIMB. 15 



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

 arm. 



The Triceps Extensor Cubiti. This is an immense muscular mass 

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

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

 guished 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 Cajyut Parvum, or small head (Plate 5), is, Avhen 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 between 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 

 supraspiuatus, 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, the first 

 into the inner surface of the shaft of the humerus above the internal 

 tubercle, the second into a line which begins on a level with the 

 internal tubercle, and runs down the anterior surface of the shaft near 

 its inner border. Between these two insertions, the pre-humeral artery 

 and the nerve to the biceps pass. The tendon of origin of the muscle 

 comes out between the supraspiuatus and subscapularis muscles, and 

 the posterior border of the muscle is related to the brachial artery. 



Action. — To adduct and flex the shoulder. 



The Biceps (Plates 5 and 6). This muscle receives its name in the 



