990 



THE NERVOUS SYSTEM 



Branches. — The ulnar resembles the median nerve in not furnishing any 

 branches to the upper arm. As it passes between the olecranon process and the 

 medial condyle it gives off two or three fine filaments to the elbow-joint. In 

 the upper part of the forearm it supplies the flexor carpi ulnaris and the medial 

 portion of the flexor digitorum profundus, and in the lower half it gives off the 

 three cutaneous branches. In the palm of the hand it supplies the integument 

 of the M'pothenar eminence, the fifth digit, and half of the fourth digit, and part 

 of the skin of the dorsum. It also supplies the short intrinsic muscles of the 

 hand with the exception of the abductor poUicis, the opponens, the lateral head 

 of the flexor pollicis brevis, and the two lateral lumbricales. 



The nerves to the flexor carpi ulnaris and to the medial two divisions of the flexor digitorum 

 profundus arise from the ulnar nerve in the upper third of the forearm. 



Cutaneous branches. — About the middle of the forearm the ulnar nerve gives off two 

 cutaneous branches: — one pierces the fascia and anastomoses with the volar branch of the 

 medial antibrachial (internal) cutaneous nerve, and the other, the palmar cutaneous branch, 

 runs downward in front of the ulnar artery (fig. 759) and is conducted by this vessel into the palm 



Fig. 760. — Diagrams Illustrating a Common Distribution of Cutaneous Nerves of 

 Forearm. A, dorsum; B, volar aspect. 



Ulnar branch 



of medial anti- ' 



brachial 

 cutaneous 



Dorsal cutane- 

 ous branch 

 of ulnar 



Dorsal digital 

 nerves (ulnar) 



Dorsal antibrachial 

 cutaneous (radial) 

 - Dorsal antibrachial 

 cutaneous (radial) 



\ Lateral antibrachial 

 •* cutaneous (musculo- 

 cutaneous) 



Lateral antibrachial 

 cutaneous (musculo- 

 cutaneous 



Median nerve 

 . .Superficial radial 



Superficial radial 

 From 



lateral anti- 

 brachial Dorsal 



cutaneous digital 



branches 

 of radial 

 Dorsal branches 

 of radial 



Dorsal branches of 

 proper volar die;ital 

 Dorsal nerves (median) 



-.\n branches of proper 

 volar digital 

 nerves (median) 



Ulnar branches 

 •p..'of medial anti- 

 brachial cuta- 

 neous 



Volar branches of 

 medial anti- 

 brachial cutaneus 



— Volar branch of ulnar 



_Palmar cutaneous 

 branch of ulnar 



-Palmar cutaneous 

 branch of median 



.^Cutaneous branches 

 of common volar 

 digital nerves 



- _ Proper volar 



digital nerves 

 (ulnar) 



(fig. 756). It furni.shes some filaments to the vessel, supplies a few twigs to the skin of the hypo- 

 thenar eminence, and ends in the integument covering the central depressed surface of the palm. 



The dorsal or posterior cutaneous branch, usually the smaller of the terminal branches, 

 arises about 5 cm. (2 in.) above the wrist-joint, and passes backward under cover of the flexor 

 carpi ulnaris to reach the dorsal aspect of the wrist (fig. 7G1), where it gives off delicate branches 

 to anastomose with branches of the medial antibrachial (internal) cutaneous, the dorsal anti- 

 brachial (external) cutaneous branch of the radial (nmsculo-spiral), the lateral antibrachial 

 cutaneous of the musculo-cutan(>ous nerve, and with branches of the superficial radial, and then 

 divides into five branches, the dorsal digitals (fig. 757), which are distributed to the ulnar 

 sides of the third, fourth, and fifth digits and the radial sides of the fourth and fifth digits. 

 These branches usually extend on the fifth digit only as far as the base of the terminal phalanx, 

 and on the fourth digit as far as the base of tlie second plialanx. The more distal parts of 

 these digits am supi)liod by palmar digital l)ranchcs of the ulnar nerve. 



The volar branch, the otlicr terminal branch of the ulnar nerve, continues its course between 

 the flexor carpi ulnaris anfl flexor digitorum sublimis, on the medial side of the ulnar artery, to 

 the wrist, where, on the lateral side of tlie pisiform lione, it divides into a superficial and a 

 d^ep branch (figs. 759 and 701). The latter accompanies the deep branch of the ulnar artery 

 into the interval between the abductor digiti quinti and flexor digiti quinti brevis, and then 



