790 



HUMAN ANATOMY. 



caput obliquum of the adductor, the vessel frequently divides into two branches, one of 

 which is continued distally along the radial border of the index-finger, forming what 

 has been termed the a. radialis indicis (a. volaris indicis radialis), while the other 

 extends along the first metacarpal and, passing between the two heads of the adductor, 

 divides beneath the tendon of the tiexor longus poUicis into two branches, which 

 pass distally along the palmar surface of the thumb, one along the inner and the 

 other along the outer border, anastomosing with the branches of the dorsalis pollicis. 



Variations. — The a. princeps pollicis is in reality the palmar interosseous artery of the first 

 intermetacarpal space, and, when developed as described, corresponds in the arrangemenj^of 

 its branches with the dorsalis indicis, together with the dorsalis pollicis. Frequently, however, 

 the branch to the radial border of the index-finger is lacking, or, on the other hand, it may be 

 well developed and arise directly from the deep palmar arch, or sometimes both it and the 

 princeps pollicis are derived from the superficial palmar arch (page 784). 



8. The Palmar Interosseous Arteries. — The palmar interosseous arteries 

 (aa. metacarpeae volares) are three in number, and arise from the deep palmar arch as 



Fig. 717 



Radial artery 



Anterior carpal branch 

 Superficial volar 



 . Posterior carpal branch 



Metacarpal 



Dorsales pollicis 



Radial artery 

 Princeps pollicis 



Radialis indicis 



Dorsalis indicis 

 Branch from radialis in- 

 dicis for superficial arch 



Ulnar artery 



Anterior carpal branch 



Posterior carpal branch 



Posterior carpal branch 



Posterior carpal arch 



Deep branch of ulnar 

 A perforating branch of 



deep palmar arch 

 Superficial palmar arch 

 Dorsal interosseous 



arteries 

 Palmar interosseous 



arteries 



Digital arteries 



Semidiagrammatic reconstruction of right hand, viewed from palm, showing relations of arteries 

 to surface and to bones; vessels on dorsal surface are represented in outline. 



it crosses the second, third, and fourth intermetacarpal spaces. Each artery passes 

 distally in its intermetacarpal space, resting upon the interosseous muscles, and 



