FOREARM AND HAND 143 



The branches which spring from the radial artery in this 

 part of its course are of small size. They are : 



1. The dorsal carpal. 



2. The dorsal metacarpal. 



3. The two dorsales pollicis arteries. 



4. The dorsalis indicis artery. 



The dorsal radial carpal artery takes origin on the lateral 

 aspect of the wrist, and runs medially upon the carpus to join 

 the corresponding carpal branch of the ulnar artery. The arch 

 thus formed is placed under cover of the extensor tendons, and 

 gives off two branches which run distally in the third and 

 fourth inter -metacarpal intervals. They are termed the second 

 and third dorsal metacarpal arteries. 



The first dorsal metacarpal artery arises, as a rule, from the 

 radial trunk, although not infrequently it may be seen to 

 spring from the dorsal carpal arch. It extends distally in 

 the second interosseous space. 



The three dorsal metacarpal arteries are brought into 

 connection with the arteries in the palm by communicating 

 branches. They are joined by the three perforating twigs of 

 the arcus volaris profundus. These make their appearance on 

 the dorsum between the heads of the three medial dorsal inter- 

 osseous muscles. Further, at the distal ends of the interosseous 

 spaces the dorsal metacarpal arteries usually send rami per- 

 forantes inferiores to join the corresponding common volar 

 digital arteries in the palm. 



The two dorsal arteries of the thumb run distally upon 

 either side of that digit. 



The dorsal artery of the index is distributed on the lateral 

 side of the index. 



Dorsal Carpal Ligament. This has been seen to be 

 an aponeurotic band which stretches obliquely across the wrist. 

 It is merely a thickened portion of the deep fascia, and its 

 attachments are so arranged that it does not interfere with the 

 free movement of the radius and hand during pronation and 

 supination. On the lateral side it is fixed to the lateral margin 

 of the distal end of the radius, whilst on the medial side it is 

 attached to the os triquetrum and os pisiforme, and also to the 

 palmar aponeurosis. In the case of the transverse carpal liga- 

 ment one large compartment, or tunnel, is formed for the flexor 

 tendons ; not so in the case of the dorsal carpal ligament. 

 Partitions or processes proceed from its deep surface, and 



