332 A MANUAL OF ANATOMY 



The external cutaneous branches of the musculo-spiral are two in 

 number — upper and lower. They leave the main trunk towards the 

 lower end of the spiral groove, just before the nerve passes through 

 the external intermuscular septum, and the two branches pierce 

 the deep fascia about | inch apart. The upper branch, of small 

 size, descends with the cephalic vein to the front of the elbow, 

 giving branches to the integument of the outer and anterior 

 aspects of the arm in its lower half. The lower branch, of larger 

 size, descends behind the external epicondyle into the forearm, 

 where it is distributed to the integument on the posterior aspect 

 of the outer side as low as the wrist. 



The cutaneous branch of the musculo -cutaneous pierces the 

 deep fascia on the outer side of the biceps a little above the 

 elbow. It descends behind the median cephalic vein, giving one 

 or two twigs over it, and then it divides into two branches. 

 One supplies the integument on the anterior aspect of the outer 

 side of the forearm, and the other gives branches to the integument 

 on the posterior aspect. 



The cutaneous branch of the ulnar, which arises about the 

 centre of the forearm, pierces the deep fascia, and has a limited 

 distribution to the integument just below the centre, internal to 

 the median line. This branch is inconstant. 



Superficial Veins. — There are four principal superficial veins in 

 the forearm, namely, the median, radial, anterior ulnar, and 

 fJosterior ulnar. I 



The median vein is formed by the union of a few radicles which 

 originate in the venous plexus in front of the wrist, and its course 

 is upwards in front of the forearm. As it ascends it takes uj 

 several veins, and often receives a large tributary from the bad 

 of the limb. It is also in free communication with the radial anc 

 anterior ulnar veins. On arriving at the hollow in front of th« 

 elbow it receives a short but large branch, called the deep medial 

 vein, which establishes a communication between it and the deej 

 venae comites. Thereafter it divides into median cephalic anc 

 median basilic, which diverge from each other as they ascenc' 

 somewhat like the capital letter V. The median cephalic vein, th< 

 smaller of the two, passes upwards and outwards in the interv^ 

 between the biceps and brachio-radialis, having the cutaneou 

 part of the musculo-cutaneous nerve behind, and a^ few of it 

 twigs over it. A little above the external epicondyle it receive 

 the radial vein, the resulting trunk being called the cephalic veil 

 The median basilic vein, the larger of the two, passes inwards am 

 upwards, crossing the bicipital fascia, which separates it from the^j 

 brachial artery, and the anterior branch of the internal cutaneous j 

 nerve descends behind it, a few of its twigs passing over it. Just 

 above the internal epicondyle it receives the anterior and posterior 

 ulnar veins, either separately or as a common trunk, and the resulting 

 vessel is called the basilic vein. 



