3. Fractures of both bones of the fore-arm, may occur either at the
ends, or in the middle of the limb. Frequent in the middle, and
somewhat common below, they seldom occur in its upper part, where the
fleshy portions of numerous muscles, combined with a considerable
thickness of the ulna, resist the motions which tend to produce
them. The two bones, though most commonly broken on the same line,
are, however, sometimes broken on different ones. The fracture is
almost always single: at times, however, it is double, and Desault,
in particular, was once called to a patient, over whose fore-arm the
wheels of a carriage had passed, and had broken it both in the middle
and at the lower end, so that it evidently exhibited six fragments
distinct from each other. The two middle ones, though completely
insulated, united again to the others with but very little deformity.
Like all other similar affections, these may be rendered compound by
wounds, splinters, &c. circumstances which, as they fall within the
general class of such injuries, will not be treated of at present.
14. They occur, in general, in two ways, being the result, sometimes
of the action of external bodies, immediately applied, and at other
times of the same action, operating by way of a counter-stroke. The
occasional percussion of a body on the fore-arm, furnishes an example
of the first mode of fracture. This is much more frequent, in general,
than the other, which usually arises from a fall on the wrist; but, in
such a case, as it is the large lower end of the radius that forms the
principal point of articulation with the hand, that bone alone sustains
almost all the force of the stroke, and is very generally the exclusive
seat of the fracture.
§ III.