The two forearm bones are more frequently _broken_ together than separately and generally by direct violence, the lower fragment being usually drawn up by the action of the flexor and extensor muscles and producing a swelling on the palmar surface of the forearm. Indirect violence usually causes fracture of the radius only. In both cases, but especially in fracture of both bones, there is a tendency for membrane to get between the fragments, so the arm is put up in splints with the hand midway between pronation and supination in order to separate the bones as far as possible. Care must be taken not to have the bandage too tight or gangrene of the fingers may result. In most fractures of the arm it is put up bent, but in _fracture of the olecranon_ it is put up fully extended, as the fragment is sure otherwise to be displaced by the pull of the triceps. In fact, the olecranon is sometimes fractured by the muscular force of the triceps, though usually its fracture, which is frequent, is due to direct violence. The ulna is also often fractured in the middle by direct violence or the styloid process may be broken. Fracture of the neck or shaft of the radius is very common, the most important arm fracture being that of the lower end of the radius or _Colles’ fracture_. This and the corresponding fracture in the leg, _Pott’s fracture_, are two of the commonest fractures. In _dislocation of the wrist_ the normal relation of the two styloid processes remains unchanged, but in Colles’ fracture the lower fragment often projects on the back of the hand, making a typical deformity called the _silver fork deformity_. The bones of the wrist and hand had best be described before the forearm muscles are taken up, as the muscles of the forearm are distributed largely to the fingers. =The Wrist.=--The wrist or _carpus_ is made up of eight bones arranged in two rows of four each. In the first row are the _scaphoid_ and _semilunar bones_, on the outer side, articulating with the radius, the _cuneiform_ articulating with the fibro-cartilage of the wrist-joint, and the _pisiform_. In the second row, in corresponding positions, are the _trapezium_, _trapezoid_, _os magnum_, and _unciform_. The eminence felt on the radial side of the wrist is the protuberance of the scaphoid, while the pisiform is generally felt on the ulnar side. [Illustration: FIG. 73.--Right carpal bones, dorsal surface. _T_, trapezium; _T´_, trapezoid; _7_, os magnum; _U_, unciform; _S_, scaphoid; _L_, semilunar; _C_, cuneiform; _P_, pisiform.]