35. The ulna, less frequently broken, in general, than the radius,
scarcely ever suffers alone from falls on the wrist or hand. Most
commonly its fracture is direct, and occurs, in particular, in cases
where a person in falling, extends the fore-arm for the purpose
of supporting himself, and strikes its internal part against some
resisting body.
The division, though it does take place occasionally in all parts of
the bone, occurs most frequently near to the lower end, where its
slender size, compared to that of its upper end, its more projecting
situation, and its thinner covering of soft parts, act as predisposing
causes.
36. In whatever part it may exist, the touch must readily detect it,
when the fingers are drawn along the internal surface of the ulna,
which lies almost immediately under the skin. If moved in contrary
directions, the fragments will also, by their mobility and crepitation,
disclose the nature of the injury. A depression more or less
perceptible is observed on the internal part of the fore-arm, produced
by a displacement of the fragments, which are carried towards the
radius, more particularly of the inferior fragment, as Petit has well
observed, the superior one remaining almost immoveable.
§ XI.