THE MUSCLES AND FASCIA OF THE ARM 



443 



Just below the middle of the arm, on its medial side, is an oval opening in the deep 

 fascia, which transmits the basilic vein and some lymphatic vessels. 



The Coracobrachialis (Fig. 411), the smallest of the three muscles in this region, 

 is situated at the upper and medial part of the arm. It arises from the apex of 

 the coracoid process, in common with the short head of the Biceps brachii, and from 

 the intermuscular septum between the two muscles ; it is inserted by means of a flat 

 tendon into an impression at the middle of the medial surface and border of the 

 body of the humerus between the origins of the Triceps brachii and Brachialis. 

 It is perforated by the musculocutaneous nerve. 



Biceps brachii M. 



Cephalic vein* 



Brachialis 'M .- 



Lateral antibrachial 

 cutaneous nerve 



Brachial artery and veins 



Median nerve 



^Medial antibrachial 

 &[ cutaneous nerve 



c' Basilic vein 

 c ~Ulnar nerve 



ladial nerve- 

 Dorsal antibrachial, 

 cutaneous nerve 



Radial collateral artery" 



Lateral intermuscular 

 septum of humerus 



Superior ulnar 

 collateral artery 



Medial intermuscular 

 septum of humerus 



Humerus 



Triceps brachii M. 



FIG. 413. Cross-section through the middle of upper arm. (Eycleshymer and Schoemaker. 1 ) 



Variations. A bony head may reach the medial epicondyle; a short head more rarely found 

 may insert into the lesser tubercle. 



The Biceps brachii (Biceps; Biceps flexor cubiti) (Fig. 411) is a long fusiform 

 muscle, placed on the front of the arm, and arising by two 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 Coracobrachialis. 

 The long head arises from the supraglenoid tuberosity at the upper margin of the 

 glenoid cavity, and is continuous with the glenoidal labrum. This tendon, enclosed 

 in a special sheath of the synovial membrane of the shoulder-joint, arches over 

 the head of the humerus; it emerges from the capsule through an opening close 

 to the humeral attachment of the ligament, and descends in the intertubercular 

 groove; it is retained in the groove by the transverse humeral ligament and 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 7.5 cm. of the 

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

 posterior portion of the tuberosity of the radius, a bursa being interposed between 

 the tendon and the front part of the tuberosity. As the tendon of the muscle 

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



1 A Cross-section Anatomy, New York, 1911. 



