THE UPPER LIMB- 



393 



perforating branch from the deep pahnar arch. It then descends 

 over that space towards the cleft between the index and middle 

 fingers, where it may send forward an inferior perforating branch 

 to join the fourth or outermost digital artery from the superficial 

 palmar arch. Thereafter it divides into two dorsal collateral digital 

 arteries for the contiguous sides of the index and middle fingers. 



The second and third dorsal interosseous arteries are branches of 

 the posterior carpal arch. They descend over the backs of the third 

 and fourth interosseous spaces, at the upper ends of which each 

 receives a superior perforating branch from the deep palmar arch. 

 Near the clefts between the middle and ring, and ring and little 

 fingers, they may send forwards inferior perforating branches to join 

 the second and third digital arteries from the superficial palmar 

 arch, and thereafter each divides into two dorsal collateral digital 

 arteries for the contiguous sides of the middle and ring, and ring and 

 little fingers. The dorsal digital artery of the inner side of the little 

 finger arises from the third (innermost) dorscd interosseous, or from 

 the posterior ulnar carpal. 



The arterise dorsales polllcis, two in nmnber, arise separately 

 or by a common trunk, from the radial opposite the base of the first 

 metacarpal bone, and are 

 distributed to the sides of 

 the thumb. 



The arteria dorsalis 

 indicis arises below the 

 preceding, just before the 

 radial dips between the 

 two heads of the abductor 

 indicis. It descends on the 

 outer side of the second 

 metacarpal bone, and sup- 

 plies the outer side of the 

 index finger. 



The distribution of the 

 dorsal digital arteriesceases, 

 as a rule, about the level 

 of the first interphalangeal 

 joint. 



The Interosseous Muscles. 



The interosseous muscles 

 ire seven in number, and 

 ire arranged in two groups 

 —three palmar and four 

 dorsal. The palmar inter- 

 Dssei are seen only on the 

 palmar aspect, but the 



dorsal interossei are seen on Fig. 210,— The Palmar Interosseous 

 •oth aspects of the hand. Muscles of the Right Hand. 



