772 THE NERVOUS SYSTEM. 



Branches. With the exception of the nerve to the Pronator teres, which some- 

 times arises above the elbow-joint, the median nerve gives off no branches in the 

 arm. In the forearm its branches are muscular, anterior interosseous, and palmar 

 cutaneous, and, according to Riidinger and Macalister, two articular twigs to the 

 elbow-joint. 



The muscular branches supply all the superficial muscles on the front of the 

 forearm except the Flexor carpi ulnaris. These branches are derived from the 

 nerve near the elbow. 



The anterior interosseous supplies the deep muscles on the front of the fore- 

 arm, except the inner half of the Flexor profundus digitorum. It accompanies 

 the anterior interosseous artery along the interosseous membrane, in the interval 

 between the Flexor longus pollicis and Flexor profundus digitorum muscles, both 

 of which it supplies, and terminates below in the Pronator quadratus and wrist- 

 joint. 



The palmar cutaneous branch arises from the median nerve at the lower part 

 of the forearm. It pierces the fascia above the annular ligament, and, descending 

 over that ligament, divides into two branches ; of which the outer supplies the 

 skin over the ball of the thumb, and communicates with the anterior cutaneous 

 branch of the musculo-cutaneous nerve ; and the inner supplies the integument of 

 the palm of the hand, communicating with the cutaneous branch of the ulnar. 



In the palm of the hand the median nerve is covered by the integument and 

 palmar fascia and crossed by the superficial palmar arch. It rests upon the 

 tendons of the flexor muscles. In this situation it becomes enlarged, somewhat 

 flattened, of a reddish color, and divides into two branches. Of these, the 

 external supplies a muscular branch to some of the muscles of the thumb and 

 digital branches to the thumb and index finger ; the internal supplies digital 

 branches to the contiguous sides of the index and middle and of the middle and 

 ring fingers. 



The branch to the muscles of the thumb is a short nerve which divides to 

 supply the Abductor, Opponens, and the superficial head of the Flexor brevis 

 pollicis muscles, the remaining muscles of this group being supplied by the ulnar 

 nerve. 



The digital branches are five in number. The first and second pass along the 

 borders of the thumb, the external branch communicating with branches of the 

 radial nerve. The third passes along the radial side of the index finger, and 

 supplies the First lumbricalis muscle. The fourth subdivides to supply the adjacent 

 sides of the index and middle fingers, and sends a branch to the Second lumbrical 

 muscle. The fifth supplies the adjacent sides of the middle and ring fingers, and 

 communicates with a branch from the ulnar nerve. 



Each digital nerve, opposite the base of the first phalanx, gives off a dorsal 

 branch, which joins the dorsal digital nerve from the radial and runs along the 

 side of the dorsum of the finger, to end in the integument over the last phalanx. 

 At the end of the finger the digital nerve divides into a palmar and a dorsal 

 branch, the former of which supplies the extremity of the finger, and the latter 

 ramifies round and beneath the nail. The digital nerves, as they run along the 

 fingers, are placed superficial to the digital arteries. 



The Ulnar Nerve (Fig. 413) is placed along the inner or ulnar side of the upper 

 limb, and is distributed to the muscles and integument of the forearm and hand. 

 It is smaller than the median, behind which it is placed, diverging from it in its 

 course down the arm. It arises from the inner cord of the brachial plexus, in 

 common with the inner head of the median and the internal cutaneous nerve, and 

 derives its fibres from the eighth cervical and first dorsal nerves. At its commence- 

 ment it lies to the inner side of the axillary artery, and holds the same relation 

 with the brachial artery to the middle of the arm. From this point it runs obliquely 

 across the internal head of the Triceps, pierces the internal intermuscular septum, 

 and descends to the groove between the internal condyle and the olecranon, accom- 

 panied by the inferior profunda artery. At the elbow it rests upon the back of the 



