130 THE UPPER EXTREMITY 



side of the tendon, and are yet supplied by the median 

 nerve. 



Arcus Volaris Profundus (O.T. Deep Palmar Arch). The 

 artery which takes the chief part in the formation of this 

 arch is the radial. This vessel enters the palm by passing 

 to the volar surface through the proximal part of the first 

 interosseous space between the two heads of the first dorsal 

 interosseous muscle. In the present state of the dissection 

 it makes its appearance between the contiguous margins of 

 the oblique and transverse portions of the adductor pollicis. 

 It runs medially upon the interossei muscles and the meta- 

 carpal bones immediately distal to their bases. As it ap- 

 proaches the fifth metacarpal bone it is joined by the deep 

 volar branch of the ulnar artery, and in this manner the deep 

 volar arch is completed. 



The deep volar arch does not show so strong a curve as 

 the superficial volar arch, and it is placed at a more proximal 

 level in the palm. It is closely accompanied by the deep 

 branch of the ulnar nerve ; and is separated from the super- 

 ficial volar arch by the group of flexor tendons and their 

 sheaths, the lumbrical muscles, the branches of the median 

 nerve which occupy the intermediate compartment of the 

 palm, and also, at its medial end, by the short flexor of the 

 fifth digit, dorsal to which the deep volar branch of the 

 ulnar artery passes to join the radial. 



The branches which spring from the deep volar arch are : 

 (i) the recurrent a few small twigs which run proximally in 

 front of the carpus to anastomose with branches of the volar 

 carpal arch ; (2) perforating branches, which pass dorsally in 

 the upper parts of the interosseous spaces to anastomose with 

 the dorsal metacarpal arteries ; and (3) the volar metacarpal 

 branches three in number which pass distally, volar to the 

 interosseous spaces, and unite, near the roots of the fingers, 

 with the corresponding common volar digital arteries from the 

 superficial volar arch. Sometimes these branches enlarge 

 and take the place of the corresponding common volar 

 digital arteries. 



Dissection. To bring the arteria volaris indicis radialis and the arteria 

 princeps pollicis into view, the parts of the adductor pollicis must be 

 detached from their origins and turned laterally. The radial artery is 

 now seen passing volarwards between the two heads of the first dorsal 

 interosseous muscle. 



