welling in the region of the ossifying junction, with oedema of the
overlying skin and dilatation of the superficial veins.

The swelling appears earlier and is more definite in superficial bones
such as the tibia, than in those more deeply placed such as the upper
end of the femur. It may be less evident to the eye than to the fingers,
and is best appreciated by gently stroking the bone from the middle of
its shaft towards the end. The maximum thickening and tenderness usually
correspond to the junction of the diaphysis with the epiphysis, and the
swelling tails off gradually along the shaft. As time goes on there is
redness of the skin, especially over a superficial bone, such as the
tibia, the swelling becomes softer, and gives evidence of fluctuation.
This stage may be reached at the end of twenty-four hours, or not for
some days.

Suppuration spreads towards the surface, until, some days later, the
skin sloughs and pus escapes, after which the fever usually remits and
the pain and other symptoms are relieved. The pus may contain blood and
droplets of fat derived from the marrow, and in some cases minute
particles of bone are present also. The presence of fat and bony
particles in the pus confirms the medullary origin of the suppuration.

If an incision is made, the periosteum is found to be raised from the
bone; the extent of the bare bone will be found to correspond fairly
accurately with the extent of the lesion in the marrow.

_Local Complications._--The adjacent joint may exhibit symptoms which
vary from those of a simple effusion to those of a purulent _arthritis_.
The joint symptoms may count for little in the clinical picture, or, as
in the case of the hip, may so predominate as to overshadow those of the
bone lesion from which they originated.

_Separation and displacement of the epiphysis_ usually reveals itself by
an alteration in the attitude of the limb; it is nearly always
associated with suppuration in the adjacent joint.

When _pathological fracture_ of the shaft occurs, as it may do, from
some muscular effort or strain, it is attended with the usual signs of
fracture.

_Dislocation_ of the adjacent joint has been chiefly observed at the
hip; it may result from effusion into the joint and stretching of the
ligaments, or may be the sequel of a purulent arthritis; the signs of
dislocation are not so obvious as might be expected, but it is attended
with an alteration in the attitude of the limb,