338 



APPLIED ANATOMY. 



shape with its base upward. The styloid process of the radius forms its base ; 

 the extensor brevis pollicis with the extensor ossis nietacarpi pollicis forms its radial 

 or outer side, and the tendon of the extensor longus pollicis forms its ulnar or inner 

 side. Its floor is formed by the navicular (scaphoid) and trapezium bones. 

 Through it, lying on these bones and the external lateral ligament, passes the radial 

 artery on its way to the first interosseous space. Superficial to the artery lies a 

 vein and some fine branches of the radial nerve. In ligating the artery at this point, 



Radial vein 

 Posterior radial tubercle 



Extensor ossis metacarpi pollicis 

 and extensor brevis pollicis 



Extensor carpi radialis longior 



Extensor carpi radialis brevior 



Radial artery in snuff-box 



Extensor longus pollicis 



Abductor indicis 



Posterior ulnar vein 



Posterior annular ligament 



FIG. 348. View of the anatomical snuff-box and the radial artery passing through it. 



care should be taken not to mistake the vein for it ; the vein is near the skin, the 

 artery lies deep on the lateral ligament and bones (Fig. 348). 



SURFACE ANATOMY OF THE WRIST. 



The bellies of many of the muscles, mainly the superficial ones, cease as they 

 become tendinous about the middle of the forearm. Hence the rapid decrease 

 in size as one descends. When the wrist is reached there is a swelling on each side 

 caused by the expanded lower end of the radius on the outer side and the head of 

 the ulna on the inner. The medial (inner) prominence is rendered more marked by 

 abducting the hand, the lateral (outer) prominence by adducting it. Just beyond 

 these there is a constriction as the wrist passes into the hand. 



