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.
OF THE REDUCTION, AND THE MEANS OF MAINTAINING IT.
37. The reduction does not differ from that of the radius (31), except in this, that the assistant who makes the extension, must place the hand in the opposite state, namely, that of abduction, in order that the fragments may be brought into contact, while the surgeon assists in this process, by pushing the broken ends of the bone in a direction opposite to that of their displacement.
As in the foregoing case, three splints are sufficient for the apparatus, where the radius, being unbroken, performs the office of a fourth.
The exercise of the limb, after the consolidation of the bone, is in general less necessary here, than in fractures of the radius (34), because the ulna, being an immoveable point of support for the motions of rotation, concurs in them only in a passive manner.
FRACTURE OF THE OLECRANON.
§ XII.