et with in which relapses recur
at regular intervals for several years, the tendency, however, being for
the attacks to become milder as the virulence of the organisms becomes
more and more attenuated.

_Clinical Features._--Osteomyelitis in a patient over twenty-five is
nearly always of the relapsing variety. In some cases the bone becomes
enlarged, with pain and tenderness on pressure; in others there are the
usual phenomena which attend suppuration, but the pus is slow in coming
to the surface, and the constitutional symptoms are slight. The pus may
escape by new channels, or one of the old sinuses may re-open.
Radiograms usually furnish useful information as to the condition of the
bone, both as it is altered by the original attack and by the changes
that attend the relapse of the infective process.

_Treatment._--In cases of thickening of the bone with persistent and
severe pain, if relief is not afforded by the repeated application of
blisters, the thickened periosteum should be incised, and the bone
opened up with the chisel or trephine. In cases attended with
suppuration, the swelling is incised and drained, and if there is a
sequestrum, it must be removed.

#Circumscribed Abscess of Bone--"Brodie's Abscess."#--The most important
form of relapsing osteomyelitis is the circumscribed abscess of bone
first described by Benjamin Brodie. It is usually met with in young
adults, but we have met with it in patients over fifty. Several years
may intervene between the original attack of osteomyelitis and the onset
of symptoms of abscess.

_Morbid Anatomy._[7]--The abscess is nearly always situated in the
central axis of the bone in the region of the ossifying junction,
although cases are occasionally met with in which it lies nearer the
middle of the shaft. In exceptional cases there is more than one abscess
(Fig. 120). The tibia is the bone most commonly affected, but the lower
end of the femur, or either end of the humerus, may be the seat of the
abscess. In the quiescent stage the lesion is represented by a small
cavity in the bone, filled with clear serum, and lined by a fibrous
membrane which is engaged in forming bone. Around the cavity the bone is
sclerosed, and the medullary canal is obliterated. When the infection
becomes active, the contents of the cavity are transformed into a
greenish-yellow pus from which the staphylococcus can be isolated, and
the cavity is lined by a thin film of granulation tissue whic