hey owed their origin to the
liquefaction of a solid tumour, such as a myeloma, a chondroma, or even
a sarcoma. Although the tissue elements in this disease resemble those
of a new growth arising in the marrow, they differ in their arrangement
and in their method of growth; there is no tendency to erupt through the
cortex of the bone, to invade the soft parts, or to give rise to
secondary growths.

_Clinical Features._--The onset of the disease is insidious, and
attention is usually first directed to it by the occurrence of fracture
of the shaft of one of the long bones--usually the femur--from violence
that would be insufficient to break a healthy bone. Apart from fracture,
the great increase in the size of one of the long bones and its uneven
contour are sufficiently remarkable to suggest examination with the
X-rays, by means of which the condition is at once recognised. A
systematic examination of the other long bones will often reveal the
presence of the disease at a stage before the bone is altered
externally.

Symmetrical bossing of the skull was present in the case shown in
Figs. 136 and 137, and there were also scattered patches of brown
pigmentation of the skin of the face, neck, and trunk, similar to those
met with in generalised neuro-fibromatosis. Apart from fracture, the
disease is recognised by the thickening and usually also by the curving
of the shafts of the long bones. It is easy to understand the curvature
of bones that have passed through a soft stage and also of those that
have been broken and badly united, but it is difficult to account for
the curvatures that have no such cause; for example, we have seen
marked curve of the radius in a forearm of which the ulna was quite
straight. The curvature probably resulted from exaggerated growth in
length.

[Illustration: FIG. 137.--Radiogram of Upper End of Femur showing
appearances in Osteomyelitis Fibrosa.]

The X-ray appearances vary with the stage of the malady, not estimated
in time, for the condition is chronic and may become stationary, but
according to whether it is progressive or undergoing repair. The shadow
of the bone presents a poor contrast to the soft parts, and no trace of
its original architecture; in extreme cases the shadow of the femur
resembles an unevenly filled sausage (Fig. 137); there is no cortical
layer, the interior shows no trabecular structure, and some of the many
clear areas are probably cysts. The condition extends rig