ostitis and osteomyelitis--Tuberculosis--
Syphilis--Tumours.

#Suppurative Periostitis and Osteomyelitis.#--These conditions may be
the result of infection through the blood stream, but as a rule they
follow upon a breach of the surface caused by a wound, a severe burn
as in epileptics, a tertiary syphilitic ulcer, or a compound fracture
that has become infected. Sometimes they follow suppuration in the
middle ear and mastoid or in the frontal sinus, and epithelioma and
rodent cancer that has ulcerated and become infected after spreading
from the face towards the vertex. They are occasionally associated
with acute cellulitis of the scalp. When the infection is blood-borne
suppuration occurs on both aspects of the bone--a point of importance
in treatment.

The illness is usually ushered in by a rigor, and this is soon
followed by other signs of suppuration--high temperature, pain and
tenderness, and the formation of a fluctuating swelling in relation to
the bone. When pus forms between the bone and the dura, there is a
characteristic oedema of the overlying area of the scalp--spoken of as
_Pott's puffy tumour_--which is of value as indicating the extent of
the disease in the bone, and of the collection of pus between it and
the dura. When suppuration occurs under the pericranium, an incision
gives exit to a quantity of pus, and exposes an area of bare bone. If
the incision is made early, this bone may soon be covered by
granulations and recover its vitality; but if operation is delayed, it
usually undergoes necrosis. The sequestrum that forms includes, as a
rule, only the outer table, but in some cases the whole thickness of
the bone undergoes necrosis. In either case the separation of the
sequestrum is an exceedingly slow process, and is not accompanied by
the formation of new bone. When the whole thickness of the skull is
lost, there may be a protrusion of the contents of the skull--hernia
cerebri; should the patient survive, the gap becomes filled in by a
dense fibrous membrane which is fused with the dura mater.

Serious complications, in the form of meningitis, cerebral abscess,
sinus phlebitis, and general pyaemia, are liable to develop at any time
during the progress of the infection, and we have seen pyaemia develop
after the suppuration in the skull had been recovered from.

_Treatment._--Early, free, and, if necessary, multiple incisions are
indicated to admit of disinfection of the affected area, and o