388 A MANUAL OF ANATOMY. 



carpal arch the second and third dorsal interosseous arteries 

 are distributed to the third and fourth interosseous spaces. 

 (2) The first dorsal interosseous, or the metacarpal : a small 

 branch from the radial under the tendon of the extensor 

 longus pollicis, to the space between the second and third 

 metacarpal bones. (3) The dorsalis pollicis and (4) the 

 dorsalis indicis are small arteries distributed to the dorsal 

 surface of the thumb and index fingers. The dorsalis pol- 

 licis divides into two branches to either side of the thumb, 

 while the dorsalis indicis supplies the outer side of the index 

 finger. 



The Collateral Digital Arteries. 



The dorsal digital arteries divide at the web of the fingers 

 into small branches to the adjacent sides of the dorsal 

 surface of the fingers. 



The posterior carpal branch of the ulnar is found issu- 

 ing from the front of the forearm under the tendon of the 

 flexor carpi ulnaris muscle. It passes to the back of the 

 wrist and enters into the posterior carpal anastomoses. See 

 above. 



The Dorsal Interossei. Fig. 79. 



These are four in number, one on either side of the 

 middle finger, one to the radial side of the index, and one 

 to the ulnar side of the ring finger respectively. 



Origin. By two heads from the contiguous sides of the 

 metacarpal bones between which they lie. The origin is 

 more extensive from that metacarpal bone of the finger 

 into which they are inserted. 



Insertion. Into the base of the first phalanx, and into 

 the lateral margin of the tendon of the extensor communis 

 digitorum. 



