es, although not in all, after reduction has been
effected, the bones retain their proper relations without external
support, a point in which a dislocation differs from a fracture. A
careful investigation of the kind of force which produced the injury,
particularly as regards its intensity and direction of action, may aid
in the diagnosis. The diagnosis can always be verified by the use of
the Roentgen rays, and this should be had recourse to whenever
possible, as a fracture may be shown that otherwise would escape
recognition.

_Prognosis._--After having once been dislocated, a joint is seldom as
strong as it was formerly, although for all practical purposes the
limb may be as useful as ever. Some degree of stiffness, of limited
movement, or of muscular weakness, and occasional arthritic changes
and a liability to re-dislocation, are the commonest sequelae.
Prolonged immobilisation is liable to lead to stiffness by permitting
of the formation of adhesions; while too early movement tends to
produce a laxity of the ligaments which favours re-displacement from
slight causes.

_Treatment._--Reduction should be attempted at the earliest possible
moment. Every hour of delay increases the difficulty. The guiding
principle is to cause the displaced bone to re-enter its socket by
the same route as that by which it left it--that is, through the
existing rent in the capsule. This is done by carrying out certain
manipulations which depend upon the anatomical arrangement of the
parts, and which vary, not only with different joints, but also with
different varieties of dislocation of the same joint. In general terms
it may be said that the main impediments to reduction are: the
contraction of the muscles acting upon the displaced bone; the
entanglement of the bone among tendons or ligamentous bands which fix
it in its abnormal position; and the rent in the capsule being small
or valvular, so that it forms an obstacle to the bone reentering the
socket.

Muscular contraction is best overcome by the administration of a
general anaesthetic, and in all but the simplest cases this should be
given to ensure accurate and painless reduction. Failing this,
however, the muscles may be wearied out by the surgeon making steady
and prolonged traction on the limb, while an assistant makes
counter-extension on the proximal segment of the joint. Advantage may
also be taken of such muscular relaxation as occurs when the patient
is already faint