142 THE UPPER EXTREMITY 



supply directly from the radial nerve (O.T. musculo-spiral). 

 The anconaeus also derives its main nerve of supply from 

 the radial, but it also frequently obtains a second twig from 

 the dorsal interosseous nerve. 



Terminal Branch of the Arteria Inter ossea Volaris. 

 The terminal or perforating branch of the volar inter- 

 osseous artery is a vessel of some size. It appears through 

 the interosseous membrane, about two inches or so proximal to 

 the distal end of the forearm. Accompanied by the dorsal 

 interosseous nerve it runs distally under cover of the 

 extensor pollicis longus, and ends on the dorsum of the 

 carpus by anastomosing with the dorsal carpal arch and 

 the dorsal interosseous artery. 



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 radial artery and its branches. 



2. The dorsal carpal ligament. 



3. The extensor tendons of the fingers. 



Radial Artery. It is only a small portion of the radial 

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

 of the radius the vessel turns dorsally below 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 (Fig. 54, p. 139). 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 venae, comites and some fine filaments 

 from the lateral cutaneous nerve of the forearm which twine 

 around it. 



