f 



THE BRA CHIAL PLEXUS 1039 



The Ulnar Nerve ('//. id nans'] (Figs. 758 and 764) is situated along the inner or 

 ulnar side of the upper limb, and is distributed to the muscles and integument 

 of the forearm and hand. It is smaller than the median, behind which it is 

 placed, diverging from it in its course down the arm. It arises from the inner 

 cord of the brachial plexus, in common with the inner head of the median and the 

 internal cutaneous nerves, and derives its fibres from the eighth cervical and first 

 thoracic nerves. At its origin it lies to the inner side of the axillary artery, and 

 holds the same relation with the brachial artery to the middle of the arm. Here 

 it pierces the intermuscular septum, runs obliquely across the internal head of 

 the Triceps, and descends to the groove between the internal condyle and the olec- 

 ranon, accompanied by the inferior profunda artery. At the elbow it rests upon 

 the back of the inner condyle, and passes into the forearm between the two heads 

 of the Flexor carpi ulnaris muscle. In the forearm it descends in a perfectly 

 straight course along the ulnar side of the extremity, lying upon the Flexor pro- 

 fundus digitorum muscle, its upper half being covered by the Flexor carpi ulnaris 

 muscle, its lower half lying on the outer side of the muscle, being covered by the 

 integument and fascia. In the upper third of its course, it is separated from the 

 ulnar nerve by a considerable interval, but in the rest of its extent the nerve lies 

 to the inner side of the artery. At the wrist the ulnar nerve crosses the annular 

 ligament on the outer side of the pisiform bone, to the inner side of and a little 

 behind the ulnar artery, and immediately beyond this bone divides into two 

 branches, the superficial and the deep palmar. 



Branches. The branches of the ulnar nerve are: 



C Articular (elbow). 



Muscular. . . 



In the forearm J Cutaneous. In the hand / Superficial palmar. 



Dorsal cutaneous. I Dee P P almar ' 



^ Articular (wrist). 



The articular branches to the elbow-joint consist of several small filaments. 

 They arise from the nerve as it lies in the groove between the inner condyle of the 

 humerus and the olecranon. 



The muscular branches (rami musc'ulares), two in number, arise from the trunk 

 of the nerve near the elbow; one supplies the Flexor carpi ulnaris; the other, the 

 inner half of the Flexor profundus digitorum. 



The cutaneous branches are two in number, palmar and dorsal. 



The palmar cutaneous branch (ramus cutaneus palmaris] arises from the ulnar 

 nerve at about the middle of the forearm and runs downward on the ulnar artery, 

 giving oft' some filaments entwining around the vessel. Just above the annular 

 ligament it pierces the deep fascia and ends in the integument of the palm, com- 

 municating with the palmar cutaneous branch of the median nerve. 



The dorsal cutaneous branch (ramus dorsalis mamis) arises about two inches 

 above the wrist; it passes posteriorly beneath the Flexor carpi ulnaris, perforates 

 the deep fascia, and, running along the ulnar side of the back of the wrist and hand, 

 divides into branches (mi. digitales dorsales); one of these supplies the inner side 

 of the little finger; a second supplies the adjacent sides of the little and ring fingers; 

 a third joins the branch of the radial nerve which supplies the adjoining sides of 

 the middle and ring fingers, and assists in supplying them; a fourth is distributed 

 to the metacarpal region of the hand, communicating with a branch of the radial 

 nerve. 



On the little finger the posterior digital branches extend only as far as the base 

 of the terminal phalanx, and on the ring finger as far as the base of the second 

 phalanx; the more distal parts of these digits are supplied by posterior branches 

 derived from the palmar digital branches of the ulnar. 



