RADIAL AND ULNAR ARTERIES. 



223 



by three tendons: in the first instance by 

 two of these placed closely side by side, the 

 extensores ossis metacarpi and primi internodii 

 pollicis ; but by the third, the extensor se 

 cundi internodii, only just before the artery 

 enters the palm: so that between these two 

 crossings, the vessel runs obliquely downward 

 in the bottom of a groove, which is bounded 

 on each side by these tendons, and whose 

 depth is greatly increased by the action of the 

 muscles with which they are continuous. It 

 finally leaves the back of the hand, by passing 

 between the processes of origin of the abduc- 

 tor indicis. 



(c.) In the palm. The vessel having per- 

 forated the metacarpal space, is situated very 

 deeply in the palm of the hand, beneath the 

 flexor brevis pollicis and the different struc- 

 tures superficial to this muscle ; namely, the 

 tendons of the flexores sublimis and profundus 

 digitorum, with the lumbricales muscles, the 

 branches of the median nerve, and, above 

 these, the palmar fascia and integuments. 

 Immediately giving off its magna pollicis and 

 radialis indicis branches, it now crosses the 

 palm as the deep palmar arch, or " palmaris 

 profunda," which, slightly convex forwards, 

 lies on the proximal extremities of the meta- 

 carpal bones, and on the interossei muscles 

 between them ; being directed at right angles 

 to them towards the inner side of the hand, 

 and joined in the fourth metacarpal space by 

 the communicating branch of the ulnar, which 

 completes the arterial circle. This latter part 

 is of course uncovered by flexor brevis pol- 

 licis, and, just at its junction with the com- 

 municans ulnae, it might almost be considered 

 as covered by the flexor brevis minimi digiti. 



Branches of the radial artery. Amid very 

 numerous ramifications, the following are 

 those whose constancy and size require a 

 separate mention. 



(1.) Arteria radialis recurrens. This large 

 branch is given off from the outer side of the 

 radial trunk almost immediately upon its 

 origin from the brachial artery, and whilst it 

 is contained in the triangular hollow before 

 referred to. It passes at first downwards, 

 then outwards, and finally upwards ; lying on 

 the supinator brevis and brachialis anticus 

 successively ; and then occupying the groove 

 between the biceps and supinator radii longus 

 muscles, but overlapped by the latter, it ter- 

 minates in the arm by anastomosing with the 

 superior profunda, which descends to meet it 

 after passing beneath the outer head of the 

 triceps. It has thus a curved course, the 

 convexity of which is directed downwards 

 towards the wrist. Its branches are very 

 numerous, and chiefly supply the muscles 

 with which it is in contact, inosculating with 

 the vessels which they derive from other 

 sources, and with the superior profunda as 

 aforesaid. 



(2.) Arteria superficialis voice, which usually 

 comes off from the artery just as it leaves the 

 lower border of the radius to turn around the 

 wrist; and, directed almost vertically down- 

 wards, proceeds over the annular ligament 



and immediately beneath the integuments, 

 until it arrives at the muscles of the thenar 

 eminence ; amongst or upon which it passes, 

 crossing them at an oblique angle, to join the 

 termination of the palmar artery, or, in other 

 words, to complete the superficial palmar 

 arch. Liable to very considerable though un- 

 important deviations in its exact position, 

 perhaps one of the most constant is that 

 where the abductor pollicis lies over the ves- 

 sel, itself placed upon the flexor brevis and 

 opponens muscles. Its varieties in point of 

 size are chiefly connected with the relative 

 proportions of the other arteries, and are de- 

 ferred to them ; but it is usually a very small 

 branch, and, quite as frequently as not, ends 

 in these muscles without any direct junction 

 with the superficial palmar arch. 



(3.) Arteria anterior carpi radialis. This 

 is ordinarily a minute branch which comes oft 

 from the radial, either very close to the pre- 

 ceding, or a little above it. It runs directly 

 inwards in contact with the anterior ligament 

 of the wrist joint, or on the radius at a level 

 just above this ; to join with a similar branch 

 from the ulnar on the opposite side of the 

 wrist, and with the terminations of the an- 

 terior interosseous artery. It supplies the 

 carpal bones and the articulation. 



(4.) The arteria dorsalis carpi radialis, or 

 posterior carpal branch, is considerably larger 

 than the preceding, and is given off from the 

 radial at a lower level, generally while the 

 artery lies in the deep groove formed by the 

 tendons of the extensors of the thumb. Its 

 course is, like that of the anterior carpal, di- 

 rectly inwards beneath the tendons of the 

 different fingers; and like it, at about the 

 middle of the wrist, it terminates by uniting 

 with a similar branch from the ulnar artery, 

 and with the terminal ramifications of the in- 

 terosseous vessels. Its size and arched shape 

 are usually much more distinct than those 

 of the anterior carpal vessels. 



Other small branches are given off from the 

 radial immediately previous to its entering 

 the palm. Thus an arteria dorsalis pollicis is 

 usually present, and divides, after a short 

 course, into a branch for each side of the 

 thumb ; and there generally exists a similar 

 twig for the radial side of the index finger, 

 either as a separate branch from the radial 

 artery, or from the ulnar division of the bi- 

 furcation just mentioned. A larger branch 

 runs along the interosseous muscle in the 

 second metacarpal space, to divide at its an- 

 terior extremity into branches for the opposed 

 sides of the index and middle fingers. The 

 vessels occupying the third and fourth spaces, 

 with the same ultimate distribution, rarely 

 arise from the radial ; more usually they come 

 from the posterior carpal arch, and sometimes 

 from the previous metacarpal vessel, or from 

 a similar ulnar branch lying in the fourth 

 space. All these metacarpal branches unite, 

 at the superior extremity of the interosseous 

 space, with the deep arch by means of its 

 posterior perforating branches ; and at its 

 inferior termination, with the digital branches 



