538 THE ARTERIES 



into two branches which anastomose across the palm. (E) The arteries of the thumb and radial 

 side of the index linger may be jriven oflF from the arch. (F) The arch may be incomplete, the 

 inner digital branches coming off from the ulnar, and tlie outer from the superficial volar, the 

 radial in the palm or an enlarged median artery. (G) The arch may be absent, the lateral digital 

 arteries being then given off from enlarged interosseous arteries from the deep arch, or fiom 

 enlarged dorsal interosseous arteries. 



The branches of the superficial palmar arch are: — (1) The four digital 

 arteries; (2j the inu.<(ul;ir: and (3) the cutaneous. 



(1) The digital arteries, usually four in number, are given off from the con- 

 vexity of the superticial arch and, running downwards through the palm, supply 

 both sides of the little, ring, and middle lingers, and the ulnar side of the index 

 finger. The radial side of the index finger and the thumb are supplied respectively 

 by the radialis indicis and princeps pollicis, branches of the radial artery. The 

 digital arteries are named, from within outwards — first, second, third, and fourtli. 

 The first digital artery runs downwards and iuAvards over the muscles on the inner 

 side of the palm, and thence along the ulnar side of the little finger. It gives 

 branches to the abductor, flexor brevis, and opponens minimi digiti muscles. This 

 branch sometimes comes from the deep Ijranch of the ulnar artery. The second, 

 third, and fourth digital arteries run downwards in the interspace between the 

 little and ring, the ring and middle, and the middle and index fingers respectively, 

 to within about a quarter of an inch of the clefts Ijetween the fingers, where they 

 divide into two branches (collateral digital) for the supply of the sides of the 

 contiguous fingers. As the digital arteries pass through the palm, they lie between 

 the flexor tendons, on the digital nerves and lumbrical muscles, and beneath the 

 palmar fascia. Just before bifurcating they pass under the superficial transverse 

 ligament, and are joined by the palmar interosseous branches from the deep palmar 

 arch (fig. 354). At this spot they also receive the anterior perforating branches 

 from the dorsal interosseous vessels. On the sides of the fingers the collateral 

 digital arteries lie between the palmar and dorsal digital nerves. They anastomose 

 by small branches, forming an arch across the front of the bones on the proximal 

 side of each interphalangeal joint. They supply the flexor tendons and the integu- 

 ments, and terminate in a plexiform manner beneath the pulp of the finger and 

 around the matrix of the nail. A dorsal digital branch is given off to the back of 

 the fingers about the level of the middle of the first phalanx, and a second but 

 smaller dorsal digital branch about the level of the middle of the second phalanx. 



(2) The muscular branches from the superficial arch are very small and 

 supply the superficial muscles. 



(3) The cutaneous branches supply the integuments of the palm. 



The deep branch of the ulnar arter}', also called the communicating artery, 

 sinks deeply into the palm between the abductor and flexor brevis minimi digiti, 

 and joins the radial to form the deep palmar arch. (See The Radial ARTf:RV. 

 page 543. ) 



THE RADIAL ARTERY 



The radial artery — the smaller of the two arteries into which the brachial 

 divides at the bend of the elbow — appears as the direct continuation of the brachial. 

 It runs downwards and outwards along the radial side of the forearm as far as the 

 styloid process, then, coiling over the external lateral ligament and outer and back 

 part of the wrist, enters the palm of the hand from behind between the first and 

 second metacarpal bones, and ends by anastomosing with the dee}) l)ranch of the 

 ulnar to form the deep palmar arch. Hence the artery is divisible into three parts: 

 that in the forearm, that at the wrist, and that in the palm of the hand. The 

 course of the artery is indicated by a line drawn from a point one inch below the 

 centre of the elbow to a ])()int situated half an inch internal to the styloid process 

 of the radius. 



I. The Radial Artery in the Forearm 



In its course through the forearm (fig. 351) the radial artery is found in the 

 outermost intermuscular space, and it is only necessary to divide the skin, super- 



