292 Palm of Hand 



abductor, flexor brevis, and adductor pollicis ; if manipulations then 

 fail it may be necessary to divide the abductor and the outer head 

 of flexor brevis before the phalanx can be replaced. Sometimes the 

 capsule of the joint or the intervention of the tendon of the long flexor 

 is the impediment to reduction. 



The palmaris brevis arises from the inner part of the anterior 

 annular ligament, and is inserted into the skin along the inner border 

 of the hand, which it raises to form the cup of Diogenes. Crossing 

 over the ulnar vessels and nerve, it is supplied by the superficial part 

 of the ulnar nerve. 



In the ball of the thumb the most superficial muscle is the 

 abductor pollicis, which arises from the annular ligament and is in- 

 serted with the flexor brevis into the outer part of the base of the first 

 phalanx, through the medium of a sesamoid bone. 



The opponens is so named because its action is to 'place the 

 thumb opposite ' the other digits ; it is, therefore, inserted along the 

 outer side of the metacarpal bone itself. It arises from the annular 

 ligament and the trapezium, lying beneath the abductor. 



The flexor brevis has a bulky origin from the annular ligament, 

 the trapezium, os magnum, and the bases of the second and third 

 metacarpal bones. Its outer head is inserted with the abductor, and 

 its inner with the adductor pollicis, into the sides of the base of the 

 first phalanx, through the medium of sesamoid bones. The tendon of 

 the long flexor passes down between its heads of insertion. 



The adductor arises from the middle metacarpal bone*, and is in- 

 serted with the inner head of the short flexor. 



Nerve-supply. The muscles of the ball of the thumb are supplied 

 by the median, but the deep part of the flexor brevis, and the adductor 

 pollicis are supplied by the deep part of the ulnar nerve. 



The muscles of the little finger are the abductor, flexor brevis, and 

 opponens. They arise from the pisiform region of the hand. Two of 

 them are inserted into the base of the first phalanx, and the opponens 

 is inserted into the metacarpal bone itself. They are supplied by the 

 deep part of the ulnar nerve. 



Of the interossei, four are dorsal and three palmar. The former are 

 abductors, as is shown by looking at the outermost of them, which, 

 lodged between the first and second metacarpal bones, constitutes the 

 abductor indicis. The dorsal interosseous arise from two bones, and 

 between the heads of origin of each passes an artery. In the case of 

 the abductor indicis the artery is the radial, in the case of the others 

 it is the perforating of the deep arch. The interossei are inserted 

 partly into the bases of the first phalanges, helping to flex those 

 phalanges, and partly into the extensor tendons, helping, therefore, to 

 extend the second and third phalanges, as is shown on p. 273. 



In the third month of fcetal life the flattened distal end of the lappet 

 or bud, A, B, from which the arm is developed, shows four notches, c 



