THE ULNAR ARTERY 



579 



interosseous before its division, (ii) The nutrient arteries of the radius and uhia are usually- 

 derived from this vessel, (iii) The volar terminal division of the volar interosseous artery passes 

 either in front of or behind the pronator quadratus, but in either case in front of the interos- 

 seous membrane, and anastomoses with the volar carpal branches of the radial and vimar 

 arteries, and with the recurrent branches from the deep volar arch, formmg the so-called 

 volar carpal rate, (iv) The dorsal terminal, the larger division, pierces the interosseous mem- 

 brane, and continues its course downward behind the interosseous membrane, under cover of 

 the extensor muscles, to the back of the wrist, where it ends by anastomosing with the dorsal 



Fig. 471. — The Back of the Left Forearm, with the Dorsal Interosseous Artery 



AND Branches of the Radial at the Back of the Wrist. 



(From a dissection in the Hunterian Museum.) 



Articular branch of the profunda 

 Brachialis 



Brachio-radialis, cut 



Common extensor tendon 



Extensor carpi radialis longus and 

 brevis 



Supinator 

 Dorsal interosseous artery 



Abductor pollicis longus 



Brachio-radialis, cut 



Extensor pollicis brevis 



Dorsal carpal ligament 



Extensor carpi radialis longus 



Radial artery 



First dorsal metacarpal artery 



Extensor pollicis longus m 

 rsal interosseous muscle /f J 



First dorsal 



First dorsal metacarpal artery 



Princeps pollicis artery 



Dorsal digital artery 



Triceps 



Rete over olecranon 

 Interosseous recurrent artery 

 Anconeus, cut 



Extensor carpi uLnaris 

 Flexor carpi ulnaris 



Origin of extensor pollicis longus and 

 indicis proprius 



Dorsal branch of volar interosseous 



artery 

 Interosseous membrane 



Dorsal ulnar carpal artery 

 Extengor carpi radialis brevis 

 Dorsal radial carpal artery 



Fourth dorsal metacarpal artery 

 Third dorsal metacarpal artery 

 Second dorsal metacarpal artery 



carpal branches of the radial and ulnar arteries, forming the so-called dorsal carpal rete. 

 This branch anastomoses, as soon as it pierces the interosseous membrane, with the dorsal 

 interosseous artery. 



(6) The dorsal interosseous artery [a. interossea dorsahs], the larger division of the com- 

 mon interosseous, turns backward through the triangular interval bounded by the interosseous 

 membrane below, the obhque hgament above, and the ulna on the medial side, and emerging 

 at the back of the forearm between the abductor pollicis longus and the supinator, under cover 

 of the superficial extensors of the forearm, descends between the superficial and the deep muscles, 

 crossing in this course the abductor polhcis longus, the extensor poUicis brevis, the extensor 

 pollicis longus, and the extensor indicis proprius (fig. 471). It anastomoses at the lower border 



