470 THE MUSCLES AND FASCIAE 



huraerus, and the anterior circumflex vessels; by its inner border, with the brachial artery, and 

 the median and musculocutaneous nerves; by its outer border, with the short head of the Biceps 

 and Brachialis anticus. 



The Biceps, or the Biceps flexor cubiti (m. biceps brachii), is a long fusiform 

 muscle, occupying the whole of the anterior surface of the arm, and divided above 

 into two portions or heads, from which circumstance it has received its name. 

 The short head (caput breve} arises by a thick flattened tendon from the apex of 

 the coracoid process, in common with the Coracobrachialis. The long head 

 (caput lonrjum)arises from the upper margin of the glenoid cavity, and is continu- 

 ous with the glenoid ligament. This tendon arches over the head of the humerus, 

 being enclosed in a special sheath of the synovial membrane of the shoulder-joint ; 

 it then passes through an opening in the capsular ligament at its attachment to 

 the humerus, and descends in the bicipital groove, in which it is retained by a 

 fibrous prolongation from the tendon of the Pectoralis major. Each tendon is 

 succeeded by an elongated muscle belly, and the two bellies, although closely 

 applied to each other, can readily be separated until within about three inches 

 of the elbow-joint. Here they end in a flattened tendon, which is inserted into. 

 the back part, of the tuberosity of thp ra^jns a synovial bursa, being interposed 

 between the tendon and the front of the tuberosity; another bursa is. often inter- 

 posed between the ulna and the tendon. As the tendon of the muscle approaches 

 the radius it becomes twisted upon itself, so that its anterior surface becomes 

 external and is applied to the tuberosity of the radius at its insertion; opposite 

 the bend of the elbow the tendon gives off, from its inner side, a broad aponeurosis, 

 the bicipital fascia (lacertus fibrosus], which passes obliquely downward and in- 

 ward across the brachial artery, and is continuous with the deep fascia covering 

 the origins of the superficial Flexor muscles of the forearm (Fig. 34^). 1 



Relations. Its superficial surface is overlapped above by the Pectoralis major and Deltoid; 

 in the rest of its extent it is covered by the superficial and deep fasciae and the integument. Its 

 deep surface rests above on the shoulder-joint and upper part of the humerus; below it rests on 

 the Brachialis anticus, with the musculocutaneous nerve intervening between the two, and on 

 the Supinator [brevis]. Its inner border is in relation with the Coracobrachialis, and overlaps 

 the brachial vessels and median nerve; its outer border, with the Deltoid and Brachioradialis. 



The Brachialis anticus (m. brachialis) is a broad muscle, which covers the 

 elbow-joint and the lower half of the front of the humerus. It is somewhat com- 

 pressed from before backward, and is broader in the middle than at either extrem- 

 ity. It arises from the lower half of the outer and inner surfaces of the shaft 

 of fhp hiimerns, and commences above at the insertion of the Deltoid, whicli it. 

 embraces by two angular processes. Its origin extends below, to within an inch 

 of the margin of the articular surface, and is limited on each side by the external 

 and internal borders of the shaft of the humerus. It also arises from the inter- 

 muscular septa on each side, but more extensively from the inner, frornwnich It 

 is separated below by the Brachioradialis and Extensor carpi radialis longior. 

 Its fibres converge to a thick tendon, which is inserted jnto a rough depression on 

 the anterior surface of the coronoid process of the ulna, being received into an 

 interval between two fleshy slips of the Flexor profurioTus digitorum. 



Relations. By its superficial surface, with the Biceps, the brachial vessels, musculocutaneous 

 and median nerves; by its deep surface, with the humerus and front of the elbow-joint; by its 

 inner border, with the Triceps, ulnar nerve, and Pronator teres, from which it is separated by 

 the intermuscular septum; by its outer border, with the musculospiral nerve, radial recurrent 

 artery, the Brachioradialis, and Extensor carpi radialis longior. 



into the bicipital fascia and inner side of the tendon of the Biceps. In most cases this additional slip parses 

 behind the brachial artery in its course down the arm. Occasionally the third head consists of two slips which 

 pass down, one in front of, the other behind, the artery, concealing the vessel in the lower half of the arm. 



