THE ANTERIOR HUMERAL REGION. 



387 



perforated by the musculo-spiral nerve and superior profunda artery. The internal 

 intermuscular septum, thicker than the preceding, extends from the lower part of the 

 posterior lip of the bicipital groove below the Teres major, along the internal supra- 

 con dylar ridge to the inner condyle ; it is blended with the tendon of the Coraco- 

 brachialis, and affords attachment to the Triceps behind, and the Brachialis anticus 

 in front. It is perforated by the ulnar nerve and the inferior profunda and anasto- 

 motic arteries. At the elbow the deep fascia is attached to all the prominent 

 points round the joint viz. the condyles of the humerus and the olecranon process 

 of the ulna and is continuous with the deep fascia of the forearm. Just below the 

 middle of the arm, on its inner side, in front of the internal intermuscular septum, 

 is an oval opening in the deep fascia which transmits the basilic vein and some 

 lymphatic vessels. On the removal of this fascia the muscles, vessels, and nerves 

 of the anterior humeral region are exposed. 



The Coraco-brachjalis, the smallest of the three muscles in this region, is sit- 

 uated at the upper and inner part of the arm. It arises by fleshy fibres from 

 the apex of the coracoid process, in common with the short head of the Biceps, 

 and from the intermuscular septum between the two muscles ; the fibres pass 

 downward, backward, and a little outward, to be inserted by means of a flat ten- 

 don into an impression at the middle of the inner surface and internal border of 

 the shaft of the humerus between the origins of the Triceps and Brachialis 

 anticus. It is perforated by the musculo-cutaneous nerve. The inner border of 

 the muscle forms a guide to the position of the brachial artery in tying the vessel 

 in the upper part of its course. 



Relations. By its anterior surface, with the Pectoralis major above, and at 

 its insertion with the brachial vessels and median nerve which cross it ; by its 

 posterior surface, with the tendons of the Subscapularis, Latissimus dorsi, and 

 Teres major, the inner head of the Triceps, the humerus, and the anterior circum- 

 flex vessels ; by its inner border, with the brachial artery, and the median and 

 musculo-cutaneous nerves ; by its outer border, with the short head of the Biceps 

 and Brachialis anticus. 



The Biceps (Biceps flexor cubiti) is a long fusiform muscle, occuping 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 arises by a 

 thick flattened tendon from the apex of the coracoid process, in common with the 

 Coraco-brachialis. The long head arises from the upper margin of the glenoid 

 cavity, and is continuous with the glenoid ligament. This tendon arches over 

 the head of the humerus, being enclosed in a special sheath of the synovial mem- 

 brane 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 muscular 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 ten- 

 don, which is inserted into the back part of the tuberosity of the radius, a 

 synovial bursa being interposed between the tendon and the front of the tuber- 

 osity. 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 ten- 

 don gives off, from its inner side, a broad aponeurosis, the bicipital fascia (semi- 

 lunar fascia], which passes obliquely downward and inward across the brachial 

 artery, and is continuous with the deep fascia of the forearm (Fig. 229). The 

 inner border of this muscle forms a guide to the position of the vessel in tying 

 the brachial artery in the middle of the arm. 1 



1 A third head to the Biceps is occasionally found (Theile says as often as once in eight or nine 

 subjects), arising at the upper and inner part of the Brachialis anticus, with the fibres of which it 

 is continuous, and inserted into the bicipital fascia and inner side of the tendon of the Biceps. In 

 most cases this additional slip passes behind the brachial artery in its course down the arm. Occa- 

 sionally the third head consists of two slips which pass down, one in front, the other behind the artery, 

 concealing the vessel in the lower half of the arm. 



