Chondromas springing from the pelvic bones usually arise in the region
of the sacro-iliac joint; they project into the pelvis and press on the
bladder and rectum, and on the sciatic and obturator nerves; sometimes
also on the iliac veins, causing oedema of the legs. They are liable to
take on malignant characters, and rarely lend themselves to complete
removal by operation.

#Fibroma# is met with chiefly as a periosteal growth in relation to the
mouth and pharynx, the _simple epulis_ of the alveolar margin and the
_naso-pharyngeal polypus_ being the most common examples. We have met
with a fibroma in the interior of the lower end of the femur of an
adult, causing expansion of the bone with decided increase in girth and
liability to pathological fracture; it is possible that this represents
the cured stage of osteomyelitis fibrosa.

_Myxoma_, _lipoma_, and _angioma_ of bone are all rare.

#Myeloma.#--The myeloid tumour, which is sometimes classified with the
sarcomas, contains as its chief elements large giant cells, like those
normally present in the marrow. On section these tumours present a
brownish-red or chocolate colour, and, being highly vascular, are liable
to haemorrhages, and therefore also to pigmentation, and to the formation
of blood cysts. Sometimes the arterial vessels are so dilated as to
impart to the tumour an aneurysmal pulsation and bruit. The enlargement
or "expansion" of the bone results in the cortex being represented by a
thin shell of bone, which may crackle on pressure--parchment or
egg-shell crackling.

The myeloma is most often met with between the ages of twenty-five and
forty in the upper end of the tibia or lower end of the femur. It grows
slowly and causes little pain, and may long escape recognition unless an
examination is made with the X-rays. Although these tumours have been
known to give rise to metastases, they are, as a rule, innocent and are
to be treated as such. When located in the shaft of a long bone,
pathological fracture is liable to occur.

_Diagnosis and X-ray Appearances of Myeloma._--The early diagnosis of
myeloma is made with the aid of the X-rays: the typical appearance is
that of a rounded or oval clear area bounded by a shell of bone of
diminishing thickness (Fig. 145). The inflammatory lesions at the ends
of the long bones--tubercle, syphilitic gumma, and Brodie's abscess,
that resemble myeloma, are all attended with the formation of new bone
in greater or l