FOREARM AND HAND 191 



end of the radius. It is traversed by tendons of the extensor 

 digitorum communis and the tendon of the extensor indicis 

 proprius and their mucous sheath, and by the terminal 

 parts of the dorsal interosseous nerve and the perforating 

 branch of the volar interosseous artery. The fifth compart- 

 ment is situated over the interval between the distal ends of 

 the radius and ulna. It contains the slender tendon of the 

 extensor digiti quinti proprius and its mucous sheath. The 

 sixth and most medial compartment^ which corresponds with the 

 groove on the dorsum of the distal end of the ulna, encloses 

 the tendon of the extensor carpi ulnaris and its mucous 

 sheath (see Fig. 76). 



Dissection. After the compartments of the dorsal carpal 

 ligament and their contents have been examined displace the 

 various tendons as far as may be necessary, and clean the dorsal 

 part of the radial artery and its branches. The artery enters 

 the dorsal part of the wrist region by curling round the lateral 

 border of the wrist deep to the tendons of the abductor pollicis 

 longus and the short and long extensors of the thumb, and it 

 disappears into the palm, at the proximal end of the first inter- 

 osseous space, between the two heads of the first dorsal inter- 

 osseous muscle. As it lies at the side of the wrist two dorsal 

 arteries of the thumb and the dorsal radial carpal branch spring 

 from it, and just before it disappears it gives off the dorsal artery 

 to the index finger, and the first dorsal metacarpal artery, unless 

 that branch rises in common with the dorsal radial carpal artery. 



Radial Artery. Only a small portion of the radial 

 artery is seen in this dissection. At the distal end of 

 the radius the vessel turns dorsally, distal to the styloid 

 process and upon the radial collateral ligament of the 

 radio-carpal joint. Having gained the dorsal aspect of the 

 carpus, it runs distally upon the navicular and os mult- 

 angulum majus, and finally disappears from view by turning 

 volarwards, through the proximal part of the first interosseous 

 space and between the heads of origin of the first dorsal 

 interosseous muscle (Figs. 75, 76). In the palm it takes the 

 chief share in the formation of the deep volar arch. 



While the radial artery rests on the radial collateral 

 carpal ligament, it is deeply placed, and is crossed by the 

 tendons of the abductor pollicis longus and the extensor 

 pollicis brevis. On the carpus it lies nearer the surface, 

 and is crossed obliquely by the extensor pollicis longus. It is 

 accompanied by two vena comites and some fine filaments from 

 the lateral cutaneous nerve of the forearm which twine around it. 



