ULXAR AXD MEDIAN XEEVES. 649 



side of the pisiform bone. Above the wrist it gives off a large dorsal branch 

 to the hand, and continuing onwards it enters the palm on the surface of 

 the annular ligament, and divides into muscular and cutaneous branches. 

 The ulnar nerve gives off no branches in the upper arm. 



A. Branches in the forearm : 



a. Articular filaments are given to the elbow-joint as the nerve passes behind it. 

 Some filaments are also given to the wrist-joint. 



b. Muscular branches. One branch enters the upper part of the flexor carpi 

 ulnaris, and another supplies the two inner divisions of the deep flexor of the fingers.* 



c. Cutaneous branches to the forearm. These two small nerves arise about the 

 middle of the forearm by a common trunk. One pierces the fascia, and turning 

 downwards, joins a branch of the internal cutaneous nerve. This branch is often 

 absent. The second, a palmar branch, lies on the ulnar artery, which it accompanies 

 to the hand. This little nerve gives filaments around the vessel, and ramifies in the 

 integument of the hand, joining in some cases with other cutaneous offsets of the 

 ulnar or median nerve. 



d. Dorsal branch to the hand. This, large offset, leaving the trunk of the ulnar 

 nerve two or three inches above the wrist, winds backwards beneath the flexor carpi 

 ulnaris and divides into branches ; one of these ramifies on the inner side of the 

 little finger, another divides to supply the contiguous sides of that finger and the 

 ring finger, while a third joins on the back of the metacarpus with the branch of the 

 radial nerve which supplies the contiguous sides of the ring and middle finger. The 

 several posterior digital nerves, now described, are united with twigs directed back- 

 wards from the anterior digital nerves of the same fingers. 



B. Palmar branches: 



a. The deep branch separates from the trunk beyond the annular ligament, and, 

 dipping down through the muscles of the little finger in company with the deep 

 branch of the ulnar artery, it follows the course of the deep palmar arch across the 

 hand. It supplies the short muscles of the little finger as it pierces them ; and as it 

 lies across the metacarpal bones, it distributes two branches to each 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 

 thumb and the index finger the nerve ends in branches to the adductor pollicis, and 

 the inner head of the flexor brevis pollicis. 



b. 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 lower part 

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

 dorsal aspects. 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 interosseous muscles of the 

 hand, the two internal lumbricales, the adductor pollicis and the inner 

 half of the flexor brevis pollicis. Lastly, it contributes to the nervous 

 supply of the elbow and wrist joints. 



MEDIAN NERVE. 



The median nerve arises by two roots, one from the outer, the other from 

 the inner cord of the brachial plexus. Commencing by the union of these 



* A case has been recorded in which tlie ulnar nerve supplied also two branches to the 

 flexor sublimis digitorum (Turner, " Kat. Hist. Review," 1864). 



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