the
vertebral border of the scapula, and the cristal border of the ilium.
They exhibit a rough symmetry; they rarely attain any size; and they
usually cease growing when the skeleton attains maturity--the conversion
of cartilage into bone being then completed. While they originate from
the ossifying junctions of the long bones, they tend, as the shaft
increases in length, to project from the surface of the bone at some
distance from the ossifying junction and to "point" away from it. They
may cause symptoms by "locking" the adjacent joint or by pressing upon
nerve-trunks or blood vessels.

In a considerable proportion of cases, the disturbance of growth is
further manifested by dwarfing of the long bones; these are not only
deficient in length but are sometimes also curved and misshapen, which
accounts for the condition being occasionally confused with the
disturbances of growth resulting from rickets. In about one-third of the
recorded cases there is a dislocation of the head of the radius on one
or on both sides, a result of unequal growth between the bones of the
forearm.

[Illustration: FIG. 140.--Multiple Cartilaginous Exostoses in a
man aet. 27. The scapular tumour projecting above the right clavicle has
taken on active growth and pressed injuriously on the cords of the
brachial plexus.]

In early adult life, one of the tumours, instead of undergoing
ossification, may take on active growth and exhibit the features of a
chondro-sarcoma, pressing injuriously upon adjacent structures (Fig. 140)
and giving rise later to metastases in the lungs.

The _X-ray appearances_ of the bones affected are of a striking
character; apart from the outgrowths of bone or "tumours" there is
evident a widespread alteration in the internal architecture of the
bones, which suggests analogies with other disturbances of ossification
such as achondroplasia and osteomyelitis fibrosa. The condition is one
that runs in families, sometimes through several generations; we have
more than once seen a father and son together in the hospital
waiting-room.

As regards _treatment_, there is no indication for surgical interference
except when one or other tumour is a source of disability as by pressing
upon a nerve-trunk or by locking a joint, in which case it is easily
removed by chiselling through its neck.

[Illustration: FIG. 141.--Multiple Cartilaginous Exostoses in a
man aet. 27, the same as in Fig. 140.]

_Diffuse Osteoma, Leontiasis O