RADIAL AT THE WRIST 541 



than usual, into the supinator lonjjjus and pxtcnsor carpi radialis longior and 

 brevior, and anastomoses with tlie interosseous recurrent. A second ascends he- 

 tAveen the l)rachiahs anticus and supinator longus, with the nnisculo-spiral nerve, 

 and anastomoses with the superior profunda artery. A third descencls with the 

 radial nerve under cover of the sujnnator longus su])plying that muscle. The radial 

 recurrent also gives off brandies to the elbow-joint. 



(2) The muscular branches of the radial artery come off irregularly to 

 sui)ply the contiguous muscles on the outer side of the forearm. 



(3) The anterior radial carpal arises from the inner side of the radial artery 

 about the level of the lower l)order of the pronator quadratus. It crosses the front 

 of the radius beneath the flexor muscles, and anastomoses with the anterior carpal 

 branch of the ulnar, forming what is sometimes called the anterior carpal arch; or 

 Avhat is, more properly speaking, an arterial plexus or rete — the anterior carpal 

 rete. This plexus is joined aljove by small twigs from the anterior interosseous 

 artery, and below by recurrent branches from the deep palmar arch. It supplies 

 branches to the lower end of the radius, and to the Avrist and carpal joints. 



(4) The superficial volar leaves the radial artery as the latter vessel is about 

 to turn over the external lateral ligament to the back of the wrist. It courses 

 forwards over the short muscles of the ball of the thumb, and anastomoses with 

 the superficial branch of the ulnar artery to com})lete the superficial palmar arch. 

 It su))plies small branches to the muscles of the ball of the thumb, and at times 

 terminates in these muscles without joining the arch. Occasionally it passes beneath 

 the abductor pollicis. This brancli is often small and ends in the muscles of the 

 thumb. 



II. The Radial Artery at the Wrist 



The radial artery at the wrist winds over the outer side of the carpjus, under the 

 extensor tendons of the thumb, from a spot a little below and internal to the styloid 

 ]jrocess of the radius to the base of the first interosseous space, where it sinks 

 ijetween the two heads of the abductor indicis into the palm, to form, by anasto- 

 mosing with the deep branch of the ulnar artery, the deep palmar arch. A line 

 drawn from half an inch internal to the styloid process to the base of the first inter- 

 (jsseous space, which can be distincth' felt on the back of the hand, will roughly 

 indicate the course of the artery. 



Relations. — The artery is covered successively by the extensor ossis metacarpi 

 pollicis and extensor jirimi internodii pollicis, by branches of the radial nerve and 

 su])erficial radial veins, and, just before it sinks between the two heads of the 

 abductor indicis, by the tendon of the extensor secundi internodii pjollicis. The 

 branches of the radial nerve to the thumb and index finger cross it. It is at first 

 somewhat deeply placed beneath the first-mentioned extensor muscles of the thumb; 

 but sul)se(]uently it lies quite superficial, and can be felt pulsating in a little trian- 

 gular depression bounded on either side by the extensor ynimi and extensor secundi 

 internodii p>ollicis, and above by the lower end of the radius. The artery lies suc- 

 cessively on the external lateral ligament of the Avrist, on the scai)hoid, the trape- 

 zium, the base of the fii'st metacarpal bone, and on the dorsal ligaments uniting 

 these bones. It has usually with it two comj)anion veins, and a few ])ranches of 

 the musculo-cutaneous nerve. 



The branches of the radial artery at the wrist arc: — (1) The posterior radial 

 car})al; (2) the metacarpal, or the first dorsal interosseous; (3) thedorsalis pollici.':. 

 or dorsal artery of the thumb; and (4) the dorsalis indicis, or dorsal digital artery 

 of the first finger. 



(1) The posterior radial carpal arises from the radial as the latter vessel 

 passes under the extensor ossis metacarpi pollicis, and runs inwards l)eneath the 

 extensor carpi radialis longior and brevior, and the extensor secundi internodii 

 pollicis, across the back of the carpus, to anastomose with the posterior ulnar car] >al 

 and with the terminal twigs of the posterior branch of the anterior interosseous 

 artery. This anastomosis is called the ]iosterior carpal arch, or jiosterior carpal 

 rete. The two following named branches are given off from this an^h or rete: — 

 (a) The second and (b) the third dorsal interosseous arteries to the third 

 and fourth spaces respectively. These vessels run downwards on the dorsal inter- 



