THE FOREARM 



1159 



It will be seen that the anastomotica magna is the artery most largely employed, 

 distributing branches everywhere, save to the front of the external condyle. 



THE FOREARM 



Bony landmarks. — The ulna can be easily traced down from the olecranon to 

 the styloid i)rocess; the bone becomes somewliat rounded below, and lies between 

 the flexor and extensor carpi ulnaris. The tip of the styloid process corresponds 

 to the inner end of the line of the wrist-joint. The radius is covered above by the 

 brachio-radialis and radial extensors of the carpus, and the outline of the bone is 

 less easily followed. Its styloid process is readily made out below, a finger's 

 breadth above the thenar eminence. It is placed on a slightly lower level than 

 that of the styloid process of the ulna. Thus, a line drawn straight between the 

 two processes would fall a little below that of the wrist-joint, this being shown l)y 

 a line drawn between the two processes forming a slight curve, with its concavity 



Fig. 723.~Section THBouGn the >rinni.E of the Right Forearm. (Heath.) 



Anterior inter- 

 osseous ve^feU 

 and .VEUVE 



Radial vesseU 

 and SERVE 



Pronator teres 



Brachio-radialie 



Supinator brevis 



Exiensor carpi radialis 

 lougior and brevior 



Extensor ossis metacarpi 

 pollicis 



Flexor sublimis digitorum 



Flexor carpi ulnaris 



Extensor communis digitorum | ' Ulnar lessels anil SERVE 



Extensor carpi ulnaris I ^^^^^^ profundus digitorum 



Posterior interosseous vessels and XERVE VEDH V \ER\'E 

 Extensor secucdi luternodii pollicis 



downwards (corresponding to the concavity of the lower surface of the radius and 

 fibro-cartilage) aV)out half an inch (12 mm.) above the straight line given above. 



The radial styloid process is covered by the extensor ossis metacarpi and 

 primi internodii pollicis, while farther out lies that of the extensor secundi. The 

 bones are nearest to each other in complete pronation, and farthest apart in com- 

 l)lete supination. On section, the l)ones are found at every point nearer to the 

 back than to the front of the limb, but increasingly so above. ' The lower the 

 section proceeds down the limb, the less will the bones be covered at the sides, and 

 the more equally will the soft parts be distributed about the anterior and posterior 

 aspects of the limb. It will be noticed tliat wliere one bone is the most substantial, 

 the other is the more slender, as near the ell)ow and wrist; and that it is about tlie 

 centre of the limb that the two are most nearly of equal strength ' (Treves). "\\'h(n 

 the limb is pronated, the interosseous space is narrowed; in supination and the mid- 

 position it is widened out. In pronation, Vtoth styloid jiroeesses can be distinctly 

 made out; in sui)ination, that of the radius is most distinct, as now the skin and 

 soft ])arts are stretched and raised over that of the ulna. 



