THE WRIST AND BACK OF HAND. 157 



owing to the tendency to motion that exists between these 

 bones, a false joint may be the result unless accurate 

 adaptation and perfect rest be maintained. 



The fractures which occur in the forearm are those 

 affecting either one or both bones and their processes. If 

 the coronoid process be fractured, a rare accident, depen- 

 dent on muscular action or dislocation, that amount of 

 flexion performed by the brachialis anticus is necessarily 

 lost ; symptoms of fracture of the olecranon are obvious, 

 and the powerful action of the triceps in separating the 

 fragments accounts for the rarity of bony union ; more- 

 over, the articulation is generally opened. If the neck 

 of the radius be fractured, a result of direct violence, the 

 diagnosis is obscure, and must be deduced from the want 

 of power of voluntary pronation and supination. 



The action of the muscles of the forearm upon fragments 

 is well marked in such a case as fracture of the shaft of 

 the radius alone. Thus, supposing it broken about its 

 centre, the upper fragment is drawn forwards by the 

 biceps, inwards by the pronator teres ; the lower frag- 

 ment is pronated and drawn downwards and inwards by 

 the pronator quadratus, and its styloid process tilted 

 upwards by the supinator longus. In fractures of both 

 bones the action of the muscles often causes great de- 

 formity. 



SURGICAL ANATOMY OF THE REGION OF THE 

 WRIST ANJ) BACK OF HAND. 



Surface Markings. Beneath the integuments are seen 

 the cutaneous veins and the tendons of the muscles act- 

 ing on the wrist and fingers, the anterior ones being 

 most evident in flexion of the hand or clenching the fist, 



14 



