200 ATLAS AND TEXT-BOOK OF HUMAN ANATOMY. 



Fig. 283. — The palmar muscles after removal of the palmar aponeurosis. 

 The tendon-sheath of the middle finger has been split lengthwise. 



Fig. 284. — The deep layer of the palmar muscles. 

 The transverse carpal ligament and the abductores digiti V and pollicis brevis have been removed. The tendons 

 of the long flexors have been removed from the carpal canal and, after splitting the tendon-sheaths of the fingers, 

 have been partly removed and partly drawn aside. 



the bottom of the carpal canal from the palmar surfaces of the lesser multangular (trapezoid) 

 and capitate (os magnum) bones, but the greater number arise from the palmar surface of the 

 shaft of the third metacarpal bone, and pass almost horizontally toward the narrow tendon of 

 insertion which is attached to the basal phalanx of the thumb by means of the ulnar sesamoid 

 bone. 



The muscle is supplied by the ulnar nerve. It adducts the thumb, i. e., approximates the thumb and index-finger. 



THE MUSCLES OF THE HYPOTHENAR EMINENCE. 



The abductor digiti quinti (Figs. 285 and 290) is the strongest and innermost muscle of the 

 group. It arises from the pisiform bone, sometimes also from the transverse carpal ligament, 

 and is inserted into the ulnar border of the dorsal aponeurosis of the little finger. 



It is supplied by the ulnar nerve, and abducts the little finger, i. c, separates the little from the ring finger. 



The flexor digiti quinti brevis (Figs. 285 and 286) arises from the transverse carpal liga- 

 ment and from the hamulus of the hamate (unciform) bone. It is a small slender muscle situated 

 to the radial side of the abductor and may be entirely absent, or fused with the opponens. Its 

 short tendon of insertion is attached beside that of the abductor into the basal phalanx of the little 

 finger. 



It is supplied by the ulnar nerve. It flexes the first phalanx of the little finger. 



The opponens digiti quinti (Figs. 283, 284, and 290) arises together with the preceding 

 muscle and runs to the ulnar border of the metacarpal bone of the little finger. 



It also is supplied by the ulnar nerve and opposes the little finger. 



THE INTEROSSEI AND THE LUMBRICALES. 



The interossei completely fill the interspaces between the metacarpal bones. Those mus- 

 cles situated nearer to the dorsal surface are known as the interossei dorsales, those nearer the 

 palmar surface as the interossei volares. 



The four interossei dorsales (Figs. 281, 285, and 289) are located in the dorsal portions 

 of the four interosseous spaces, the largest being the interosseus dorsalis primus, which is situated 

 between the metacarpal bones of the thumb and index-finger. They arise by two heads from 

 the opposite surfaces of the contiguous metacarpal bones and are the only muscles which are partly 

 visible beneath the fascia upon the back of the hand. Near the heads of the metacarpal bones 



