590 NERVES OF THE LTPER LIMB. 



interosseous space — one for the palmar, the other for the dorsal interosseous 

 muscle, and supplies filaments to the two innermost lumbricales muscles. 

 Opposite the space between the tlnnnb and the index finger the nerve ends 

 in branches to the adductor poUicis, and the inner head of the flexor brevis 

 poUicis. 



h. The remaining part of the nerve supplies a branch to the palmaris brevis 

 muscle and small twigs to the integument, and divides into two digital 

 branches. 



Digital nerves. — One of these belongs to the ulnar side of the little finger. 

 The other is connected in the palm of the hand with a digital branch of the 

 median nerve, and at the cleft between the little and ring fingers, divides into 

 the collateral nerves for these fingers. The terminal disposition of the 

 digital branches on the fingers is the same as that of the median nerve, to be 

 presently described. 



Summary. — The ulnar nerve gives cutaneous filaments to the loTver 

 part of the forearm (to a small extent), and to the hand on its palmar 

 and dorsal asjDects. It supplies the following muscles, viz., the ulnar 

 flexor of the carpus, the deep flexor of the fingers (its inner half), the 

 short muscles of the little finger with the palmaris brevis, the inter- 

 osseous muscles of the hand, the two internal lumbricales, the adductor 

 pollicis and the inner half of the flexor brevis poUicis. Lastly, it con- 

 tributes to the nervous supply of the elbow and wrist joints. 



Varieties. — ^Mien the occasional epitrochleo-anconeus muscle is present, it 

 receives a branch from the ulnar in the upper arm (Henle). From the same part 

 of the nerve also small branches have been found entering the inner head of the 

 triceps. In three instances, Gniber has found the nerve descending m front of 

 the inner condyle instead of behind. A case has been recorded in which the 

 ulnar nerve supplied also two branches to the flexor sublimis digitorum (Turner, 

 " Nat. Hist. Review," 18G1). The usual anastomosis between the digital branches 

 of the median and ulnar nerves is sometimes wanting (Henle). 



Median nerve. — The median nerve arises by two roots, one from 

 the outer, the other from the inner cord of the brachial plexus. Com- 

 mencing by the union of these roots in front or on the outer side of the 

 axillary artery, the nerve descends in contact with tlie 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 fi'om 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 beneath 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. 

 Somewhat enlarged, and of a slightly reddish colour, it here separates 

 into two parts of nearly equal size. One of these (the external) sup- 

 plies 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. Brai^ches 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 forearm (pronators and flexors), except the flexor carpi 



