300 THE SPINAL NERVES. 



inner part of the palm, joining in some cases with other cutaneous offsets of the 

 ulnar or median nerve. 



(d) Dorsal branch to the hand. This large offset (8 c). leaving the trunk of the 

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

 carpi ulnaris, gives a twig over the back of the wrist which usually joins in a loop with 

 an offset of the radial nerve, and then 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 ; a third supplies in part the contiguous sides of 

 the ring and middle fingers, and usually communicates with the branch of the radial 

 passing to the same interspace ; while a fourth is distributed to the skin of the 

 metarcarpal region of the hand, often extending to the base of the index finger 

 (fig. 201 A). The dorsal digital branches on the little finger reach as far as the 

 nail ; on the ring finger they do not usually reach beyond the second phalanx. On 

 the sides of the fingers they form communications with the corresponding volar 

 digital nerves. 



B. Branches in the palm. 



(a) The niperfiaalpartot the ulnar nerve (1 d, or 8 c, 1 d) supplies filaments to the 

 palmaris brevis muscle and the integument of the hypothenar eminence, and divides 

 into two digital branches. One of these passes to the ulnar side of the little finger ; 

 the other is connected in the palm of the hand with the innermost digital branch of 

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

 collateral nerves for these fingers. From the communicating branch with the 

 median nerve filaments are sent to the skin and vessels of the palm. The terminal 

 disposition of the digital branches on the fingers is the same as that of the median 

 nerve, to be presently described. 



(b) The deep part (8 c) sinks backwards with the deep branch of the ulnar artery 

 between the abductor and flexor brevis minimi digiti muscles, and passing to the 

 inner side of and below the hook of the unciform bone (which it sometimes grooves 1 ), 

 through the cleft in the opponens minimi digiti muscle (Vol. II, p. 238), follows the 

 course of the deep palmar arch across the hand. It supplies the short muscles of 

 the little finger as it passes between them ; as it lies over the metacarpal bones it 

 distributes branches to the interosseous muscles and the inner two lumbricales ; and 

 at the outer side of the palm it terminates in offsets to the adductores pollicis and 

 the abductor indicis muscles. Articular filaments pass upwards to the wrist, and 

 others descend to the metacarpo-phalangeal articulations (Riidinger). Rauber also 

 describes small perforating branches, which accompany the superior perforating 

 arteries in the interosseous spaces, and join the terminal filaments of the posterior 

 interosseous nerve. 



Varieties. The ulnar nerve not unfrequently has an additional root from the seventh 

 cervical nerve. It is rarely derived wholly from the eighth nerve, or from the seventh and 

 eighth cervical. In a few instances the nerve has been seen descending in front of the inner 

 condyle instead of behind. Cases are also recorded in which the ulnar nerve slipped forwards 

 over the internal condyle when the elbow was bent. A branch may pass from tLe ulnar nerve 

 in the arm to reinforce the internal cutaneous (p. 295). A communication between the ulnar 

 and median nerves in the arm was seen by Villar, and also a communication with the 

 musculo-spiral (Bull. Soc. Anat. Paris, 1888, 613). A branch from the median to join the 

 ulnar in the forearm is of frequent occurrence (p. 302). When the occasional epitrochleo- 

 anconeus muscle (Vol. II, p. 225) is present, it receives a branch from the ulnar nerve. 

 Filaments of the ulnar nerve have been found passing- to the inner part of the triceps, or to 

 the flexor sublimis digitorum, and from the deep part to the second (H. St. John Brooks, 

 Testut), or to the first lumbricalis (J. T. Wilson), or to the outer head of the flexor brevis 

 pollicis (normal according to Swan and Brooks). The dorsal branch may be smaller than 



1 W. Anderson, "A Note on the Course and Relations of the Deep Branch of the Ulnar Nerve," 

 Proc. Auat. Soc., Feb. 6, 1894. 



