MEDIAN. 643 



the nerve of Wrisberg, receiving merely a filament of communication from the 

 brachial plexus, which represents the latter nerve. In other cases, this filament 

 is wanting, the place of the nerve of Wrisberg being supplied entirely from 

 the intercosto-huraeral. 



The Median Nerve (Fig. 352) has received its name from the course it takes 

 along the middle of the arm and forearm to the hand, lying between the ulnar 

 and the musculo-spiral and radial nerves. It arises by two roots, one from the 

 outer, and one from the inner cord of the brachial plexus ; these embrace the 

 lower part of the axillary artery, uniting either in front or on the outer side of 

 that vessel. As it descends through the arm, it lies at first on the outer side 

 of the brachial artery, crosses that vessel in the middle of its course, usually 

 in front, but occasionally behind it, and lies on its inner side to the bend of the 

 elbow, where it is placed beneath the bicipital fascia, and is separated from the 

 elbow-joint by the Brachialis Anticus. In the forearm, it passes between the 

 two heads of the Pronator Radii Teres, and descends beneath the Flexor Sub- 

 limis, to within two inches above the annular ligament, where it becomes more 

 superficial, lying between the Flexor Sublimis and Flexor Carpi Eadialis, 

 covered by the integument and fascia. It then passes beneath the annular liga- 

 ment into the hand. 



Branches. No branches are given off from the median nerve in the arm. 

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

 cutaneous. 



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 branch furnished to the Pronator Eadii Teres 

 often arises above the joint. 



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

 arm, except the Flexor Carpi Ulnaris and inner half of the Flexor Profundus 

 Digitorum. It accompanies the anterior interosseous artery along the inter- 

 osseous 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. 



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 divides 

 into two branches ; of which the outer supplies the skin over the ball of the 

 thumb, and communicates with the external cutaneous nerve; and the wner sup- 

 plies the integument of the palm of the hand, anastomosing with the cutaneous 

 branch of the ulnar. Both nerves cross the annular ligament previous to their 

 distribution. 



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

 palmar fascia, and 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 branch supplying 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 subdivides to 

 supply the Abductor, Opponens, and outer 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 Lumbrical muscle. The fourth subdivides to supply the adja- 

 cent 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 



