INTEROSSEOUS MUSCLES. 



223 



between which it is placed, but most extensively from that support- 

 ing the finger upon which it acts, and the fibres converge pennatelj 



Fiff. 1S3. 



Fig. 182.— The Right Hand from behind, snovaxc the Dorsal i.ntekosseous 



MCSCLES. f 



The tendons of the extensor muscles have been removed as far as the distal ends 

 of the metacarpal bones, 1, 2, 3, and 4, the dorsal interossei muscles, in order from the 

 radial side inwards ; their expanded insertion in connection witli the extensor tendons, is 

 shown upon the first phalanges. 



Fig. 183. — The Eight Hand from before, showing the Palmar Intehossei 



Muscles, f 

 1, 2, 3, refer to the first, second, and third palmar interosseous muscles. 



to a common tendon in the middle. Each terminates in a tendon, 

 which is inserted partly into the base of the first phalanx, and partly into 

 the tendon of the common extensor muscle on the dorsum of the same 

 j)art of the finger. Two dorsal interossei are inserted into the middle 

 finger and draw it to either side ; of the remaining muscles one passes 

 to the radial side of the index-finger, and the other to the ulnar side 

 of the ring-finger ; they withdraw those fingers from the middle line of 

 the hand. 



The ^/zVsif dorsal interosseous muscle or ahdiicior indicis is larger than 

 the others ; its outer and larger head of origin arises from the ])roximaI 

 half of the ulnar border of the first metacarpal bono, the inner is 

 attached to the whole length of the second metacarpal bone, and be- 

 tween these heads there is left superiorly an interval wider than in the 

 other dorsal interosseous muscles. 



licJafions. — Between the heads of the abductor indicis the radial artery passes 

 forwards to the palm of the hand ; between those of the other dorsal interossei 

 small perforating- arterial branches are transmitted. 



The three palmar interossei muscles are adductors, drawing the 

 index, ring, and little fingers towards the middle line of the hand. They 

 are visible only from the palmar aspect of the hand, each one arising 

 from the concave part of the body of the metacarpal bone of the finger 

 on which it acts : they terminate, like the dorsal muscles, in small 



