ANTERIOR HUMERAL REGION. 381 



funda 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 condyloid 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 anastomotic arteries. At the elbow, 

 the deep fascia is attached to all the prominent points round the joint, and is 

 continuous with the fascia of the forearm. On the removal of this fascia, the 

 muscles of the anterior humeral region are exposed. 



The Coraco-brachialis, the smallest of the three muscles in this region, is situ- 

 ated 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 down- 

 wards, backwards, and a little outwards, to be inserted by means of a flat tendon 

 into a rough ridge at the middle of the inner side of the shaft of the humerus. 

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

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

 in the upper part of its course. 



Relations. By its anterior surface, with the Deltoid and 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, Latis- 

 simus Dorsi, and Teres Major, the short head of the Triceps, the humerus, and 

 the anterior circumflex 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 Sleeps 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 arises by a thick flat 

 tened 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, 

 by a long rounded tendon, which is continuous with the glenoid ligament. 

 This tendon arches over the head of the humerus, being inclosed in a special 

 sheath of the synovial membrane of the shoulder-joint ; it then pierces the cap- 

 sular 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. The fibres from this tendon form a rounded belly, and, 

 about the middle of the arm, join with the portion of the muscle derived from 

 the short head. The belly of the muscle, narrow and somewhat flattened, ter- 

 minates above the elbow in a flattened tendon, 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 tuberosity. The tendon of the muscle is thin 

 and broad ; as it approaches the radius it becomes narrow and twisted upon 

 itself, being applied by a flat surface to the back part of the tuberosity ; oppo- 

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

 aponeurosis, which passes obliquely downwards and inwards across the brachial 

 artery, and is continuous with the fascia of the forearm (Fig. 236). 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 



Relations. Its anterior 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 posterior surface rests on the shoulder-joint and 



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. Occasionally 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. 



