s lining the cavity
in which it lies, and a discharge of pus from the sinuses, so that the
mere persistence of discharge after an attack of osteomyelitis, is
presumptive evidence of the occurrence of necrosis. Where there are one
or more sinuses, the passage of a probe which strikes bare bone affords
corroboration of the view that the bone has perished. When the dead bone
has been separated from the living, the X-rays yield the most exact
information.

The traditional practice is to wait until the dead bone is entirely
separated before undertaking an operation for its removal, from fear, on
the one hand, of leaving portions behind which may keep up the
discharge, and, on the other, of removing more bone than is necessary.
This practice need not be adhered to, as by operating at an earlier
stage healing is greatly hastened. If it is decided to wait for
separation of the dead bone, drainage should be improved, and the
infective element combated by the induction of hyperaemia.

_The operation_ for the removal of the dead bone (_sequestrectomy_)
consists in opening up the periosteum and the new case sufficiently to
allow of the removal of all the dead bone, including the most minute
sequestra. The limb having been rendered bloodless, existing sinuses are
enlarged, but if these are inconveniently situated--for example, in the
centre of the popliteal space in necrosis of the femoral trigone--it is
better to make a fresh wound down to the bone on that aspect of the
limb which affords best access, and which entails the least injury of
the soft parts. The periosteum, which is thick and easily separable, is
raised from the new case with an elevator, and with the chisel or gouge
enough of the new bone is taken away to allow of the removal of the
sequestrum. Care must be taken not to leave behind any fragment of dead
bone, as this will interfere with healing, and may determine a relapse
of suppuration.

The dead bone having been removed, the lining granulations are scraped
away with a spoon, and the cavity is disinfected.

There are different ways of dealing with a _bone cavity_. It may be
packed with gauze (impregnated with "bipp" or with iodoform), which is
changed at intervals until healing takes place from the bottom; it may
be filled with a flap of bone and periosteum raised from the vicinity,
or with bone grafts; or the wall of bone on one side of the cavity may
be chiselled through at its base, so that it can be brought