SHOET MUSCLES OF THE HAND. 393 



Nerve-Supply. Median nerve (C. 6. 7.). 



Action. It acts solely on the first metacarpal bone, in the movement of opposition of the 

 thumb. 



M. Flexor Pollicis Brevis. The flexor pollicis brevis consists of two parts. 

 a. The superficial part of the muscle, partly concealed by the abductor pollicis 

 brevis, arises, by fleshy and tendinous fibres, from the distal border of the transverse 

 carpal ligament, and sometimes from the ridge of the greater multangular. 



It is inserted into the radial side of the base of the first phalanx of the 

 thumb, a sesamoid bone being present in the tendon of insertion. 



b. The deep part of the muscle (interosseus primus volaris) arises from the 

 medial side of the base of the first metacarpal bone. 



It is inserted into the medial side of the base of the first phalanx of the thumb 

 along with the adductor pollicis. 



This little muscle is deeply situated in the first interosseous space, in the 

 interval between the adductor pollicis obliquus and the first dorsal interosseous 

 muscle. It may be regarded as homologous with the volar interossei muscles, 

 with which it is in series. 



Nerve-Supply. Median nerve (C. 6. 7.). 



Actions. It is a flexor of the thumb and assists also in the movement of opposition of the 

 thumb to the fingers. 



M. Adductor Pollicis. The adductor pollicis is separated into two parts by 

 the radial artery. 



(1) The oblique head lies deeply in the palm, covered by the tendons of the long 

 flexors of the thumb and fingers. It arises by fleshy fibres from the volar surfaces 

 of the greater and lesser multangular and capitate bones, from the sheath of the 

 tendon of the flexor carpi radialis, from the volar surfaces of the bases of the 

 second, third, and fourth metacarpal bones, and from the volar ligaments con- 

 necting these bones together (Fig. 351, p. 392). 



It is inserted by a tendon, in which a sesamoid bone is developed, into the 

 medial side of the base of the first phalanx of the thumb. At its lateral border 

 a slender slip separates from the rest of the muscle, and passing obliquely, deep to 

 the tendon of the flexor pollicis longus, is inserted into the lateral side of the base 

 of the first phalanx along with the superficial part of the flexor pollicis brevis. 



(2) The transverse head, lying deeply in the palm beneath the flexor tendons, 

 .arises by fleshy fibres from the medial ridge on the volar aspect of the body of the 

 third metacarpal bone, in its distal two-thirds (Fig. 351, p. 392), and from the fascia 

 covering the interosseous muscles in the second and third spaces. 



Triangular in form, it is directed laterally, over the interossei muscles of the 

 first two spaces, to be inserted by tendon into the medial side of the base of the 

 first phalanx of the thumb along with the oblique head. 



Nerve-Supply. Deep branch of the ulnar nerve (C. 8. (T. 1.)). 

 Actions. Adduction and opposition of the thumb. 



Muscles of the Little Finger. 



The short muscles of the little finger are the adductor, opponens. and flexor 

 brevis digiti quinti. 



M. Abductor Digiti Quinti. The abductor digiti quinti is most superficial. 

 It arises from the pisiform bone and from the tendon of the flexor carpi ulnaris 

 and its ligamentous continuations (Fig. 351, p. 392). 



It is inserted by tendon into the medial side of the base of the first phalanx of 

 the little finger. 



Nerve-Supply. Deep branch of the ulnar nerve (C. 8. (T. 1.)). 



Actions. The muscle separates the little finger from the ring finger, and assists in flexion of 

 the finger at the metacarpo-phalangeal joint. 



M. Opponens Digiti Quinti. The opponens digiti quinti arises under cover 



