THE BRACHIAL PLEXUS. 1305 



wrist, accompanied by the ulnar artery, it pierces the deep fascia just above the 

 annular ligament, to the outer side of the pisiform bone, and enters the hand by 

 passing superficial to the anterior annular ligament (Fig. 1097). After crossing 

 the ligament it divides into its terminal branches, the si(perficial and the deep. 



Branches. — None are given off in the arm. In the forearm they are : («) 

 the articular, (d) the miiscjilar, (c) the cutayieous and (^) the dorsal branch to the 

 hand. The terminal branches in the hand are : ((?) the superficial 2.nA (y) the deep. 



a. The articular branch consists of one or two filaments which leave the ulnar as it lies in 

 the interval between the olecranon and the internal condyle. They pierce the internal part of 

 the capsular ligament and supply the elbow joint. 



b. The muscular branches arise from the ulnar in the immediate neighborhood of the 

 elbow and supply the flexor carpi ulnaris in toto and the ulnar half of the flexor profundus 

 digitorum. They consist of several fine twigs which leave the ulnar nerve as it lies between the 

 heads of the flexor carpi ulnaris. 



c. The cutaneous branches are two small filaments which arise by a common trunk at 

 about the middle of the forearm. One, which is inconstant, after piercing the deep fascia, runs 

 downward to inosculate with a twig from the internal cutaneous. The other, the palmar 

 cutaneous branch (r. cutaneus palmaris) (Fig. 1097 ), lies superficial to the ulnar artery, which 

 it accompanies to the hand almost as far as the superficial palmar arch. It sends filaments to 

 the ulnar artery and breaks up into a number of tiny threads which supply the integument of the 

 hypothenar region and inosculate with other cutaneous twigs of the ulnar, with the internal 

 cutaneous and with the palmar cutaneous branch of the median. 



d. The dorsal branch to the hand (r. dorsalis manus) is a good sized trunk which 

 leaves the ulnar in the upper part of the lower half of the forearm. To reach the dorsum of the 

 hand it passes downward and backward between the tendinous portion of the flexor carpi 

 ulnaris and the shaft of the ulna, giving ofif a branch over the dorsum of the wrist to supply 

 that region and inosculate with a twig from the radial nerve. Opposite the head of the ulna it 

 splits into three branches (nn. digitales dorsales) for the supply of the fingers. The ulnar or 

 inner branch courses along the inner side of the little finger to ramify in its integument as far as 

 the base of the nail. The middle branch follows the fourth metatarsal interval and divides into 

 two filaments, one extending along the radial side of the little finger as far as the base of the 

 nail and the other along the ulnar side of the ring finger as far as the proximal side of the 

 ungual phalanx. The radial or outer branch passes toward the base of the space between the 

 ring and middle fingers and inosculates with the branch from the radial nerve for the same cleft. 

 It divides into two sub-branches and in connection with the radial supplies the adjacent sides of 

 the ring and middle fingers (Fig. 1102). At the lateral aspect of the fingers all of these branches 

 inosculate with the palmar digital cutaneous nerves. 



e. The superficial terminal branch (r. superficialis n. ulnaris) (Fig. 1097) furnishes 

 small twigs to the palmaris brevis muscle, to the integument of the ball of the little finger and 

 sometimes to the fourth lumbricalis. It then divides, one of its subdivisions supplying the 

 ulnar side of the little finger while the other breaks up into two portions which course along 

 the adjoining sides of the little and ring fingers. The ultimate distribution of these filaments is 

 similar to that of the digital branches of the median nerve (page 1301). 



A twig of communication passes between the branch for the little and ring fingers and that 

 from the median for the ring and middle fingers. From the latter tiny threads are supplied to 

 the integument and vessels of the palm. 



f. The deep terminal branch (r. profundus n. ulnaris) (Fig. 1099) accompanies the deep 

 branch of the ulnar artery and sinks deeply into the palm between the abductor and flexor 

 minimi digiti muscles. It passes internal to and below the uncus of the unciform bone, in which 

 a groove for the nerve is sometimes found, crosses the palm with the deep palmar arch under 

 the deep flexor tendons and breaks up into terminal twigs on its arrival at the adductor trans- 

 versus pollicis (Fig. 1199). Muscular branches (rr. musculares) are furnished to the abductor, 

 opponens and flexor minimi digiti, the third and fourth lumbricales, the palmar and dorsal 

 interossei, the adductores obliquus and transversus pollicis and the deep head of the flexor bre- 

 vis pollicis. Articular branches are supplied to the intercarpal and metacarpo-phalangeal artic- 

 ulations and tiny perforating branches accompany the posterior perforating arteries between 

 the heads of the second, third and fourth dorsal interosseous muscles and inosculate with the 

 terminal twigs of the posterior interosseous nerve (Rauber). 



Communications. — The ulnar communicates freely and in many different situations with 

 the median and this close interlacing is paralleled by their similarity in distribudon. Both give 

 off no branches above the elbow, both supply the elbow joint, between them they supply all the 

 muscles of the flexor surface of the forearm, both send filaments to the wrist joint and the integ- 

 ument of the palm and between them all the muscles of the hand, the palmar aspect of all the 

 digits and the interphalangeal articulations are innervated. 



