FOREARM AND HAND 189 



dorsum of the distal end of the radius, to the dorsum of the 

 carpus, where it anastomoses with the end of the dorsal inter- 

 osseous artery and terminates in the dorsal carpal arterial 

 arch. As it crosses the back of the distal end of the radius 

 it lies between the bone and the mucous sheath, which 

 encloses the tendons of the extensor digitorum communis 

 and the extensor indicis. 



DORSAL ASPECT OF THE WRIST AND HAND. 



Upon the dorsal aspect of the wrist and hand the following 

 structures have still to be examined : 



1. The dorsal carpal ligament. 



2. The radial artery and its branches. 



3. The extensor tendons of the fingers. 



Ligamentum Carpi Dorsale. The dorsal carpal ligament 

 is a fascial 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 

 are attached to the ridges on the dorsal aspect of the distal 

 end of the radius, so as to form a series of six bridges or 

 compartments for the tendons. Each compartment is lined 

 by a mucous sheath which envelops the tendon or tendons 

 which pass through it, and facilitates their play between the 

 ligament and the bone. The different compartments should 

 now be successively opened up so that the arrangement of 

 the tendons with reference to the dorsal carpal ligament may 

 be studied. 



The first compartment is placed on the lateral side of the 

 base of the styloid process of the radius, and corresponds with 

 the broad oblique groove which is present in that part of the 

 bone. It contains two tendons, viz., the tendons of the abductor 

 pollicis longus and the extensor pollicis brevis, with their 

 mucous sheaths. The second compartment corresponds with 

 the most lateral groove on the dorsal aspect of the radius. 



