BRANCHES OF THE MEDIAN NERVE. 651 



roots in front or on the outer side of the axillary artery, the nerve descends 

 in contact with the brachial artery, gradually passing inwards over it, 

 and near the elbow is at the inner side of the vessel. Crossing the bend of 

 the arm it passes beneath the pronator radii teres, separated by the deep slip 

 of that muscle from the ulnar artery, and continues straight down the front 

 of the forearm, between the flexor sublimis digitorum and flexor profundus. 

 Arrived near the wrist it lies b.neath the fascia, between the tendons of the 

 flexor sublimis and that of the flexor carpi radialis. It then enters the 

 palm behind the annular ligament, and rests on the flexor tendons. Some- 

 what enlarged, and of a slightly reddish colour, it here separates into two 

 parts of nearly equal size. One of these (the external) supplies some 

 of the short muscles of the thumb, and gives digital branches to the thumb 

 and the index finger ; the second portion supplies the middle finger, and. 

 in part the index and ring fingers. 



The median nerve gives no branch to the upper arm. 



A. Branches in the forearm : 



In the forearm the median nerve supplies muscular branches, and, near 

 the wrist, a single cutaneous filament. All the muscles on the front of the 

 f jrearm (pronators and flexors), except the flexor carpi ulnaris and part of 

 the deep flexor of the fingers, are supplied from this nerve. 



a. The branches for the superficial muscles are separate twigs given off from the 

 nerve below or near the elbow-joint, but the branch furnished to the pronator teres 

 often arises above the joint. 



b. Anterior interosseous nerve. This is the longest branch of the median nerve, 

 and it supplies the deeper muscles of the forearm. Commencing at the upper part 

 of the forearm, beneath the superficial flexor of the fingers, it passes downwards 

 with the anterior interosseous artery on the interosseous membrane, and between 

 the long flexor of the thumb and the deep flexor of the fingers, to the pronator 

 quadratus muscle, in which it ends. 



c. The cutaneous palmar branch pierces the fascia of the forearm close to the 

 annular ligament, and, descending over that ligament, ends in the integument of the 

 palm about the middle : being connected by a twig with the cutaneous palmar branch 

 of the ulnar nerve. It distributes some filaments over the ball of the thumb, which 

 communicate with twigs of the radial or the external cutaneous nerve. 



B. Branches in the hand : 



a. Branch to muscles of the thumb. This short nerve subdivides into branches 

 for the abductor, the opponens, and the outer head of the flexor brevis pollicis muscle. 



b. Digital nerves. These are five in number, and belong to the thumb, and the 

 fingers as far as the outer side of the ring-finger. As they approach the clefts 

 between the fingers, they are close to the integument in the intervals between the 

 longitudinal divisions of the palmar fascia. 



The first and second nerves lie along the sides of the thumb ; and the former (the 

 outer one) is connected with the radial nerve upon the ball of the thumb. 



The third, destined for the radial side of the index finger, gives a muscular branch 

 to the first or most external lumbrical muscle. 



The fourth supplies the second lumbricalis, and divides into branches for the 

 adjacent sides of the index and middle fingers. 



The fifth, the most internal of the digital nerves, is connected by a crossing-twig 

 with the ulnar nerve, and divides to furnish branches to the adjacent sides of the 

 ring and middle fingers. 



Each digital nerve divides at the end of the finger into two branches, one 

 of which supplies the ball on the fore part of the finger ; the other ramifies 

 in the pulp beneath the nail. Branches pass from each nerve forwards and 

 backwards to the integument of the finger; and one larger than the rest 



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