306 ULNAR ARTERY. 



The Superficialis vola is given off from the radial artery while at the 

 wrist. It passes between the fibres of the abductor pollicis muscle, and 

 inosculates with the termination of the ulnar artery, completing the super- 

 ficial palmar arch. This artery is very variable in size, being sometimes 

 as large as the continuation of the radial, and at other times a mere mus- 

 cular ramusculus, or entirely wanting ; when of large size it supplies the 

 palmar side of the thumb and the radial side of the index finger. 



The Carpal branches are intended for the supply of the wrist, the ante- 

 rior carpal in front, and the posterior, the larger of the two, behind. The 

 carpalis posterior crosses the carpus transversely to the ulnar border of the 

 hand, where it inosculates with the posterior carpal branch of the ulnar 

 artery. Superiorly it sends branches which inosculate with the termination 

 of the anterior interosseous artery ; inferiorly it gives off posterior inter os- 

 seous branches, which anastomose with the perforating branches of the 

 deep palmar arch, and then run forward upon the dorsal interossei mus- 

 cles. 



The Metacarpal branch runs forward on the second dorsal interosseous 

 muscle, and inosculates with the digital branch of the superficial palmar 

 arch, which supplies the adjoining sides of the index and middle fingers. 

 Sometimes it is of large size, and the true continuation of the radial ar- 

 tery. 



The Dorsales pollicis are two small branches which run along the sides 

 of the dorsal aspect of the thumb. 



The Princeps pollicis descends along the border of the metacarpal bone, 

 between the abductor indicis and adductor pollicis to the base of the first 

 phalanx, where it divides into two branches, which are distributed to the 

 two sides of the palmar aspect of the thumb. 



The Radialis indicis is also situated between the abductor indicis and 

 the adductor pollicis, and runs along the radial side of the index finger, 

 forming its collateral artery. This vessel is frequently a branch of the 

 princeps pollicis. 



The Interossea, three or four in number, are branches of the deep pal- 

 mar arch ; they pass forward upon the interossei muscles, and inosculate 

 with the digital branches of the superficial arch, opposite the heads of the 

 metacarpal bones. 



The Perforantes, three in number, pass directly backwards between the 

 heads of the dorsal interossei muscles, and inosculate with the posterior 

 interosseous arteries. 



ULNAR ARTERY. 



The Ulnar artery, the other division of the brachial artery, crosses the 

 arm obliquely to the commencement of its middle third ; it then runs down 

 the ulnar side of the fore-arm to the wrist, crosses the annular ligament, 

 and forms the superficial palmar arch, which terminates by inosculating 

 with the superficialis vohe. 



Relations. In the upper or oblique portion of its course, it lies upon 

 the brachialis anticus and flexor profundus digitorum ; and is covered in 

 by the superficial layer of muscles of the fore-arm and by the median nerve. 

 In the second part of its course, it is placed upon the flexor profundus and 

 pronator quadratus, lying between the flexor carpi ulnaris and flexor sub- 

 limis digitorum. While crossing the annular ligament it is protected from 

 jnjury by a strong tendinous arch, thrown over it from the pisiform bone ; 



