THE RADIAL ARTERY 649 



The anterior radial carpal (ramus car pens volaris} (Fig. 464) is a small vessel 

 which arises from the radial artery near the lower border of the Pronator quad- 

 ratus, and, running inward in front of tae radius, anastomoses with the ante- 

 rior carpal branch of the ulnar artery. In this way an arterial anastomosis, the 

 anterior carpal arch (rete carpi volare) is formed in front of the wrist; it is joined by 

 branches from the anterior interosseous above, and by recurrent branches from 

 the deep palmar arch below, and gives off branches which descend to supply the 

 articulations of the wrist and carpus. 



The superficialis volae (ramus volaris superficialis) (Fig. 464) arises from the 

 radial artery, just where this vessel is about to wind around the wrist. Running 

 forward, it passes between, occasionally over, the muscles of the thumb, which it 

 supplies, and sometimes anastomoses with the palmar portion of the ulnar artery, 

 completing the superficial palmar arch. This vessel varies considerably in size; 

 usually it is very small, and terminates in the muscles of the thumb; sometimes 

 it is as large as the continuation of the radial. 



The posterior radial carpal (ramus carpeus dorsalis) (Fig. 465) is a small 

 vessel which arises from the radial artery beneath the Extensor tendons of the 

 thumb ; crossing the carpus transversely to the inner border of the hand, it anasto- 

 moses with the posterior carpal branch of the ulnar, forming the posterior carpal 

 arch (rete carpi dorsale), which is joined by the termination of the anterior inter- 

 osseous artery. From this arch are given off descending branches, the dorsal 

 interosseous arteries (aa. metacarpeae dorsales} for the second, third, and fourth 

 interosseous spaces, which run forward on the Second, Third, and Fourth dorsal 

 interossei muscles, and divide into dorsal digital branches (aa. digitales dorsales), 

 which supply the adjacent sides of the index, middle, ring, and little fingers, 

 respectively, communicating with the digital arteries of the superficial palmar 

 arch. The dorsal interosseous arteries anastomose with the perforating branches 

 from the deep palmar arch. 



The first dorsal interosseous arises beneath the Extensor tendons of the thumb, 

 sometimes with the posterior radial carpal ; running forward on the Second dorsal 

 interosseous muscle, it divides into two dorsal digital branches, which supply the 

 adjoining sides of the index and middle fingers; it forms anastomoses similar 

 to those of the two other dorsal interosseous arteries. 



The dorsales pollicis (Fig. 465) are two vessels which run along the sides of 

 the dorsal aspect of the thumb. They usually arise separately, but occasionally 

 by a common trunk, near the base of the first metacarpal bone. 



The dorsalis indicis (Fig. 465), also a small branch, runs along the radial side 

 of the back of the index finger, sending a few branches to the Abductor indicis. 



The princeps pollicis (a. princeps pollicis) (Fig. 464) arises from the radial just as 

 it turns inward to the deep part of the hand; it descends between the Abductor 

 indicis and Adductor obliquus pollicis, then between the Adductor transversus 

 pollicis and Adductor obliquus pollicis, along the ulnar side of the metacarpal 

 bone of the thumb, to the base of the first phalanx, where it lies beneath the tendon 

 of the Flexor longus pollicis and divides into two branches. These make their ap- 

 pearance between the inner and outer insertions of the Adductor obliquus pollicis, 

 and run along the sides of the palmar aspect of the thumb, forming on the palmar 

 surface of the last phalanx an arch, from which branches are distributed to the 

 integument and subcutaneous tissue of the thumb. 



The radialis indicis (a. volaris indicis radialis} (Fig. 464) arises close to the pre- 

 ceding, descends between the Abductor indicis and Adductor transversus pollicis, 

 and runs along the radial side of the index finger to its extremity, where it anasto- 

 moses with the collateral digital artery from the superficial palmar arch. At the 

 lower border of the Adductor transversus pollicis this vessel anastomoses with the 

 princeps pollicis, and gives a communicating branch to the superficial palmar arch. 



