s to obtain union by operative measures have failed.

In the tibia we have found that with the double electric saw a rod of
bone can be rapidly and accurately cut, extending well above as well
as below the site of fracture but unequally in the two directions; the
rod is then reinserted into the trough from which it was taken _with
the ends reversed_, so that a strong bridge of bone is provided at the
seat of non-union.

CLINICAL FEATURES OF SIMPLE FRACTURES

In the first place, the _history of the accident_ should be
investigated, attention being paid to the nature of the
violence--whether a blow, a twist, a wrench, or a crush, and whether
the violence was directly or indirectly applied. The degree of the
violence may often be judged approximately from the instrument
inflicting it--whether, for example, a fist, a stick, a cart wheel, or
a piece of heavy machinery. The position of the limb at the time of
the injury; whether the muscles were braced to meet the blow or were
lax and taken unawares; and the patient's sensations at the moment,
such as his feeling something snap or tear, may all furnish
information useful for purposes of diagnosis.

_Signs of Fracture._--The most characteristic signs of fracture are
unnatural mobility, deformity, and crepitus.

_Unnatural mobility_--that is, movement between two segments of a limb
at a place where movement does not normally occur--may be evident when
the patient makes attempts to use his limb, or may only be elicited
when the fragments are seized and moved in opposite directions.
_Deformity_, or the part being "out of drawing" in comparison with the
normal side, varies with the site and direction of the break, and
depends upon the degree of displacement of the fragments. _Crepitus_
is the name applied to the peculiar grating or clicking which may be
heard or felt when the fractured surfaces are brought into contact
with one another.

The presence of these three signs in association is sufficient to
prove the existence of a fracture, but the absence of one or more of
them does not negative this diagnosis. There are certain fallacies to
be guarded against. For example, a fracture may exist and yet
unnatural mobility may not be present, because the bones are impacted
into one another, or because the fracture is an incomplete one. Again,
the extreme tension of the swollen tissues overlying the fracture may
prevent the recognition of movement between the fragments. Deformi