FOREARM AND HAND 129 



and is inserted into the medial side of the base of the 

 proximal phalanx of the little finger. It is supplied by the 

 deep branch of the ulnar nerve. 



' The flexor digiti quinti brevis is composed of a single 

 fleshy belly which springs from the hook of the os hamatum and 

 the transverse carpal ligament, and is inserted into the medial 

 side of the proximal phalanx of the little finger, in common 

 with the abductor. This muscle is sometimes much reduced 

 in size, and frequently more or less completely incorporated 

 with the opponens. Its nerve supply comes from the deep 

 branch of the ulnar nerve. 



The opponens digiti quinti arises from the transverse carpal 

 ligament, and the hook of the os hamatum, and its fibres 

 spread out to obtain insertion into the entire length of the 

 medial margin of the metacarpal bone of the little finger. 

 The deep branch of the ulnar gives it its nerve of supply. 



Ramus Profundus Nervi Ulnaris (Deep Branch of the palmar 

 part of the Ulnar Nerve). This nerve springs from the parent 

 trunk on the volar aspect of the transverse carpal ligament, and 

 gives off a branch which supplies the three short muscles of the 

 little finger. Accompanied by the deep branch of the ulnar 

 artery it sinks into the interval between the abductor and 

 flexor digiti quinti brevis, and turns laterally across the palm 

 deep to the flexor tendons. Near the lateral border of the 

 palm the deep branch of the ulnar nerve breaks up into 

 terminal twigs which supply the adductor pollicis, and the first 

 dorsal interosseous muscle. In its course across the palm it 

 lies along the concavity or proximal border of the deep volar 

 arch, and sends three fine branches distally in front of the 

 three interosseous spaces. They supply the inte-rosseous 

 muscles in the spaces, while the two medial also give 

 branches to the dorsal surfaces of the two medial lumbrical 

 muscles. The third lumbrical has frequently a double nerve 

 supply, a branch from the deep part of the ulnar nerve, and, 

 not uncommonly, a second twig from the median enters its 

 volar aspect. 



The deep branch of the ulnar may, therefore, be said to 

 supply all the muscles of the palm which lie to the medial side 

 of the tendon of the flexor pollicis longus, whilst the median 

 supplies the three muscles which lie to the lateral side of that 

 tendon. There are two exceptions to this generalisation, viz. 

 the two lateral lumbrical muscles, which lie upon the medial 



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