298 THE CIRCULATORY SYSTEM. 
thus formed passes into the hand and gives origin to the 
branches described under the ulnar artery. The presence and 
size of this branch of the radial varies with the size of the ulnar 
artery, it being smaller or absent as the ulnar is larger. It is 
shown at m, Fig. 123. The radial artery (g) now turns 
gradually dorsad and passes beneath the tendon of the extensor 
brevis ‘pollicis onto the dorsum of the hand. It passes over the 
oblique groove on the dorsal surface of the base of the second 
metacarpal beneath the tendon of the extensor carpi radialis 
longus and passes between the bases of the second and third 
metacarpals into the palm of the hand. Here it passes to the 
ulnar side and anastomoses with the ulnar artery to form the 
palmar arch. 
ee of the Radial Artery. 
. A. radialis recurrens (2).—The radial recurrent arises 
in concavity of the elbow and sends a branch proximad to 
the structures in the concavity; it then continues to the radial 
side of the forearm at the elbow, supplying adjacent parts of 
the brachialis (2), the extensor carpi radialis, and the extensor 
communis digitorum. 
2. A. ulnaris recurrens (7).—The ulnar recurrent arises 
on the medial side of the tendon of the biceps and supplies 
structures in the concavity'of the elbow on the ulnar side, also 
the pronator teres (5) and proximal ends of the flexor carpi 
radialis and flexor profundis digitorum. 
3. Rami musculares.—Muscular branches’ are given off 
along the course of the artery, to adjacent muscles. A nutrient 
artery to the radius leaves the radial artery about two centi- 
meters distad of the supracondyloid foramen. 
4.. Aa interossez (anterior (/) and posterior) are given off 
usually separately between the origin of the ulnar artery and 
the biceps tendon. Sometimes they arise as a common trunk 
which soon divides. The posterior interosseous artery passes 
distad, supplying the flexor muscles of the forearm. It also 
sends a branch to the pronator teres. The anterior interos- 
seous (/) may arise from the ulnar artery. It passes dorsad to 
the interosseous membrane, on which it runs distad; sends a 
nutrient branch to the ulna, and then passes to the wrist in the 
