BRANCHES OF RADIAL ARTERY IN THE HAND. 417 



(b) The first dorsal interosseous or metacarpal branch arises be- 

 neath the extensor tendons of tlie thumb, irequently in common with the 

 posterior carpal branch, passes to the interval between the second and 

 third metacarpal bones, communicates with the corresponding perfo- 

 rating branch of the deep palmar arch, and, descending on the second 

 dorsal interosseous muscle, anastomoses with the palmar digital branch 

 at its division between the fingers. 



(c) The dorsal arteries of the thumb, two small branches, arising 

 separately or togetlier opposite the head of the metacarpal bone, run 

 upon the dorsal aspect of the bones of the thumb, one at the radial, the 

 other at the ulnar border. 



(d) The dorsal artery of the index finger, a very small branch, 

 arises lower down than the preceding, and semling branches to the ab- 

 ductor indicis, runs along the radial side of the back of tlie index finger. 



C. The branches derived from the radial after it has entered the 

 hand, are, the great artery of the thumb, the radial branch of the 

 index finger, and the large terminal branch, which forms the deep 

 palmar arch. 



(a) The large artery of the thumh (arteria princeps pollicis, — Hal- 

 le'r) arises from the radial, where it is about to turn inwards across the 

 palm of the hand. It descends in front of the abductor indicis, between 

 the metacarpal l^one of the thumb and the muscles covering it, to the 

 space between the lower ends of the flexor brevis pollicis. At that point, 

 and beneath the tendon of tlie long flexor, it divides into two collateral 

 hrmiclics, which course along the borders of the phalanges, on their 

 palmar aspect, and unite in front of the last phalanx, to form an arch 

 similar in arrangement to that on the other fingers. 



{h) The radial branch for the index finger generally arises close 

 to the large artery of the thumb ; but though constantly found, it varies 

 in size and in its mode of origin. It descends between the abductor 

 indicis and adductor pollicis muscles, and continues along the radial 

 border of the index finger, forming tlie radial collateral branch of that 

 finger, and anastomosing in the usual manner on the last phalanx 

 with the ulnar collateral branch derived from the superficial pahnar 

 arch. 



Varieties. — Or'ni'm. — In tlie observations of Richard Quain, the radial arteiy 

 was found to arise higher up than usual in nearly one case in eight. 



Course. — The radial artery more rarely deviates from its usual jjosition along 

 the fore-arm than the ulnar. It has been found lying upon the fibrous expansion 

 from the tendon of the biceps, and over the fascia of the fore-ann. instead of 

 beneath those stnictm-es. This vessel has been also oljserved on the sui-f ace of the 

 long supinator, instead of on the inner border of that muscle. In turning round 

 the -nTist, it has been seen passing over the extensor tendons of the thumb, instead 

 of within them. As was previously stated (p. 40i), the vasa abeiTantia occasionally 

 derived from the brachial or axillary arteries most commonly end by joining the 

 radial, or one of its branches. 



Branclus. — The radial rccurrejit is sometimes very large, or it may be replaced 

 by several separate branches. When the radial itself arises high up, tlie recm-- 

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

 the ulnar artery, or more rarely fi-om the interosseous. When given from the 

 brachial trimk, the radial recurrent has been foimd crossing beneath the tendon 

 of the biceps. 



The Hvpcvjicinl volar branch is small in a considerable number of cases, and is 

 lost in the short muscles of the thumb, without forming any connection with the 

 palmar arch, or with any of the digital arteries. In some instances in which it is 

 VOL. I. E E 



