380 A MANUAL OF ANATOMY 



Action. — (i) To abduct the little finger, and flex its metacarpo- 

 phalangeal joint ; and (2) to assist in extending the second and third 

 phalanges. 



2. Flexor Brevis Minimi Digiti — Origin. — (i) The inner surface 

 of the hook of the unciform bone close to its tip, and (2) the front 

 of the adjacent portion of the anterior annular ligament. 



Insertion. — The inner side of the base of the first phalanx of the 

 little finger, in common with the abductor minimi digiti. 



Nerve-supply. — The deep division of the ulnar nerve. 



Action. — To flex the metacarpo-phalangeal joint of the little finger. 



This muscle is of small size, and lies on the outer side of the ab- 

 ductor minimi digiti, from which it is separated, close to its origin, 

 by the profunda branch of the ulnar artery and deep division of 

 the ulnar nerve. 



3. Opponens Minimi Digiti — Origin. — (i) The inner surface of 

 the hook of the unciform bone underneath the preceding muscle, 

 and (2) the adjacent part of the anterior annular ligament. 



Insertion. — ^The inner margin of the shaft of the fifth metacarpal 

 bone. 



Nerve-supply. — ^The deep division of the ulnar nerve. 



Action. — ^To flex and adduct the fifth metacarpal bone. 



The muscle supports the abductor and flexor brevis minimi digiti, 

 and its deep surface is related to the interosseous muscles of the 

 fourth space. The deep branches of the ulnar artery and nerve 

 pass through it on their way to the deep part of the palm. 



Tliird Part of the Radial Artery. — The third part, which forms the 

 greater portion of the deep palmar arch, extends from the upper 

 part of the first interosseous space to about the base of the fifth 

 metacarpal bone, where it is joined by the profunda branch of the 

 ulnar. It enters the palm by passing between the two heads of the 

 abductor indicis, and then it crosses the palm, resting upon the 

 bases of the second, third, and fourth metacarpal bones, and the 

 adjacent interosseous muscles. In its course it describes a slight 

 arch, the convexity of which is directed towards the fingers, and it is 

 about ^ inch nearer the wrist than the superficial palmar arch. 

 The deep division of the ulnar nerve lies close above it. The third 

 part of the vessel is at first under cover of the adductor obliquus 

 pollicis ; it then passes between that muscle and the adductor 

 transversus pollicis ; and thereafter it lies beneath the superficial 

 and deep flexor tendons and lumbricales, where it forms the deep 

 palmar arch. 



Branches. — ^These are the arteria princeps pollicis, arteria radialis 

 indicis, three palmar interosseous, recurrent, and superior per- 

 forating, the last three coming from the deep palmar arch. 



The arteria princeps pollicis arises from the vessel immediately 

 after it emerges from between the two heads of the abductor indicis, 

 and it passes downwards along the first metacarpal bone, lying upon 

 the abductor indicis and under cover of the adductor obliquus pollicis. 

 On reaching the head of the bone it divides, under cover of the tendon 



