THE ARM. 269 



The coracobrachialis arises from the coracoid process and tendon of the short 

 head of the biceps and inserts on the inner surface of the humerus for a distance 5 to 

 7.5 cm. (2 to 3 in.) opposite the insertion of the deltoid, but extending a little lower. 

 In its course from the coracoid process, in its lower part, it is subcutaneous and pro- 

 duces a distinct muscular prominence along the anterior border of the axilla. It 

 occupies about one-third of the width of the axilla and is a guide to the brachial 

 artery. Below the edge of the anterior axillary fold it dips down to insert into the 

 bone and is covered by the biceps muscle. The inner edge of the coracobrachialis 

 is continuous with the inner edge of the biceps. When it contracts it adducts the 

 humerus and brings it forward. 



The pectoralis major, forming the anterior axillary fold, inserts into the 

 external lip of the bicipital groove from the greater tuberosity above to the insertion 

 of the deltoid below. The tendon is twisted on itself so that the lowest fibres at its 

 origin are inserted the highest, and the highest in origin are the lowest at their 

 insertion. 



The latissimus dorsi and teres major form the posterior axillary fold and 

 their manner of insertion resembles that of the pectoralis major. The tendon of the 



FIG. 28 1 . Rupture of the tendon of the long head of the biceps muscle, producing a swelling 

 comparatively low down. 



latissimus dorsi inserts into the bottom of the bicipital groove higher up than the 

 teres major. Hence near the humerus the lower edge of the posterior axillary fold 

 is formed by the teres major and its lower border marks the lower limit of the axillary 

 and the beginning of the brachial artery. 



As the pectoralis major, latissimus dorsi, and teres minor muscles insert on the 

 anterior surface of the humerus, they tend to rotate it inward as well as to adduct it. 



THE ANTERIOR SET. 



The biceps and brachialis anticus form the muscular mass on the anterior surface 

 of the arm.^ 



The biceps has no attachment to the humerus. It spans the bone and is 

 attached to the scapula above and to the radius and deep fascia of the forearm below. 

 In the lower half of the arm it lies on the brachialis anticus. The long head runs 

 up in the bicipital groove, and is covered by the tendon of the pectoralis major up to 

 the tuberosities, above that by the transverse humeral ligament up to the capsule, 

 which it perforates, and, crossing over the head of the humerus, is attached to the 

 upper edge of the rim of the glenoid cavity (Fig. 280). 



The bicipital branch of the anterior circumflex artery accompanies the tendon 

 in the bicipital groove. This tendon is comparatively rarely luxated, because it is 



