RADIAL ARTERY AND OFFSETS. 



281 



insertion. To the posterior border the fascia covering the interossei 

 muscles is united. The ligament should now be taken away to see the 

 interossei muscles. 



The INTEROSSEI MUSCLES, so named from their position between the 

 metacarpal bones, are seven in number. Two muscles occupy each space, 

 except in the first where there is only one ; they arise from the meta- 

 carpal bones, and are inserted into the first phalanx of the fingers. They 

 are divided into palmar and dorsal interossei ; but all the small muscles 

 are evident in the palm of the hand, though some project more than the 

 others. 



The palmar muscles (fig. 85), three in number, are smaller than the 

 dorsal set, and are most prominent in the palm of the hand. They arise 

 from the palmar surface of the metacarpal bones of the fingers on which 

 they act, viz., those of the fore, ring, and little fingers ; and they are in- 

 serted into the ulnar side of the fore, and the radial side of the other two 

 disits. 







b 



0) 



Fig. 85. 



Fig. 86. 



', 



THREE PALMAR INTEROSSEOUS MUSCLES. 

 a. Muscle of the little finger ; b, of the ring 

 finger ; and c, of the forefinger. 



FOUR DORSAL INTEROSSEOUH MUSCLFS. 

 d. Muscle of the forefinger, called sometimes 



abductor indicis. 



e and/. Muscles of the middle finger. 

 y. Muscle of the ring finger. 



Both sets of muscles have a similar termination (tig. 82, b) : the fibres 

 end in a tendon, which is inserted into the side of the first or metacarpal 

 phalanx, and sends an expansion to join the extensor tendon on the dor- 

 sum of the bone. 



The dorsal interossei (fig. 86) extend farther back than the palmar set, 

 and arise by two heads from the lateral surfaces of the metacarpal bones 

 between which they lie. The dorsal muscles are thus allotted to the 

 digits : two belong to the second finger, a third is connected with the 

 radial side of the fore, and the fourth with the ulnar side of the ring 

 finger. 



Action. They help to bend the metacarpo-phalangeal joints by their 



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