THE RADIAL ARTERY. 451 



Varieties. Origin. In the observations of Richard Quain, the radial artery was found 

 to arise higher up than usual in nearly one case in eight. Its origin was much more 

 frequently from the axillary, or from the upper part of the brachial, than from the lower 

 part of the latter artery. Low origin of the radial artery is much less frequent (see p. 439), 

 but it has been found arising below the upper third of the forearm (Tiedemann). 



Course. The radial artery more rarely deviates from its usual position along the forearm 

 than the ulnar. It has been found lying upon the semilunar fascia of the biceps, and over 

 the aponeurosis of the forearm, instead of beneath those structures. It occasionally turns 

 backwards over, instead of beneath, the tendons of the extensor muscles of the thumb ; and 

 in rarer cases it has been seen passing backwards over the supinator longus, above the middle of 

 the forearm, and descending across the thumb-muscles to the wrist. In casesuf iow origin 

 the radial artery passes beneath the pronator teres and the radial origin of the flexor sublimis 

 digitorum to its usual position between the tendons of the supinator longus and flexor carpi 

 radialis, and in two or three of these cases it has been seen joined by a vas aberrans as it makes 

 its appearance superficially. As has been previously stated (p. 440), the vasa aberrantia 

 occasionally derived from the brachial or axillary artery commonly end by joining the radial, 

 or one of its branches. 



She. The radial artery is sometimes much smaller than usual, and it has been seen 

 terminating in the carpal and superficial volar offsets, or in muscular offsets at a variable 

 level in the forearm. A few instances of absence of the radial artery are also recorded, the 

 brachial artery being continued directly into the ulnar-interosseous trunk, and giving off only 

 a radial recurrent branch at the usual place of division. In these cases the deficiency is 

 generally supplied by the ulnar artery in the hand, or by a large median artery ; more rarely 

 by a branch of the anterior interosseous, directed outwards in front of the wrist, or joining 

 the diminished radial trunk at the back of the hand (p. 446). 



Branches. The radial recurrent is sometimes very large, or it may be replaced by several 

 separate branches. One considerable branch occasionally passes backwards on the surface of 

 the supinator brevis muscle, and turns upwards behind the outer condyle of the humerus, 

 replacing the posterior interosseous recurrent artery. When the radial itself arises high up, 

 the recurrent artery usually comes from the residual brachial trunk, or sometimes from the 

 ulnar artery, or more rarely from the interosseous. When given from the brachial trunk, 

 the radial recurrent has been found crossing beneath the tendon of the biceps. 



The superficial volar branch is sometimes enlarged, and furnishes one or two digital 

 branches (generally to the thumb and index finger), and along with this the communication 

 with the superficial arch may be absent. This branch occasionally arises much higher than 

 usual ; and in a few cases the radial artery has been found dividing in the upper part of the 

 forearm into two branches of nearly equal size, the one of which descends into the palm of 

 the hand as the superficial volar arbery, giving off also the carpal and dorsal digital branches, 

 while the other passes backwards at a variable level, over the extensor tendons, in the manner 

 described above. 



The posterior carpal and dorsal interosseous branches of the radial are sometimes very small, 

 their place being supplied by the perforating offset of the anterior interosseous, apparently 

 by an enlargement of the ordinary anastomosis between them. 



The first dorsal interosseous branch is not unfrequently much enlarged, and furnishes the 

 collateral digital arteries to the index and middle fingers. The dorsal artery of the index 

 finger may similarly, though more rarely, supply one, or both of the collateral arteries of the 

 adjacent sides of the thumb and index finger. 



DEEP PALMAR ARCH (V). 



The deep palmar arch, the continuation of the radial artery, commences at the 

 upper end of the first interosseous space, extends transversely across the palm 

 towards the fifth metacarpal bone, and is completed by the deep branch of the 

 ulnar artery. The convexity of the arch thus formed is directed downwards. It 

 rests on the interosseous muscles and on the metacarpal bones immediately below 

 their carpal extremities, and is covered by the adductor obliquus pollicis, the flexor 

 tendons of the fingers, and the opponens and flexor brevis minimi digiti. It is 

 nearer to the carpus than the superficial arch, and differs from it in retaining its 

 size almost undiminished. It is accompanied for some distance by the deep branch 

 of the ulnar nerve, which runs from the inner end of the arch outwards. 



BRANCHES. 1. The recurrent branches ascend from the upper concave side of 

 the arch, and anastomose with the branches of the anterior carpal arch. 



VOL. II. Q G 



