here and there. Grooves and gutters are
frequently found in the bone underlying the dilated vessels.

There is a constant loud bruit in the tumour, which greatly troubles the
patient and may interfere with sleep. There is no tendency either to
natural cure or to rupture, but severe and even fatal haemorrhage may
follow a wound of the dilated vessels.

[Illustration: FIG. 70.--Cirsoid Aneurysm of Orbit and Face, which
developed after a blow on the Orbit with a cricket ball.

(From a photograph lent by Sir Montagu Cotterill.)]

The condition may be treated by excision or by electrolysis. In excision
the haemorrhage is controlled by an elastic tourniquet applied
horizontally round the head, or by ligation of the feeding trunks. In
large tumours the bleeding is formidable. In many cases electrolysis is
to be preferred, and is performed in the same way as for naevus. The
positive pole is placed in the centre of the tumour, while the negative
is introduced into the main affluents one after another.

ANEURYSM

An aneurysm is a sac communicating with an artery, and containing fluid
or coagulated blood.

Two types are met with--the pathological and the traumatic. It is
convenient to describe in this section also certain conditions in which
there is an abnormal communication between an artery and a
vein--arterio-venous aneurysm.

PATHOLOGICAL ANEURYSM

In this class are included such dilatations as result from weakening of
the arterial coats, combined, in most cases, with a loss of elasticity
in the walls and increase in the arterial tension due to
arterio-sclerosis. In some cases the vessel wall is softened by
arteritis--especially the embolic form--so that it yields before the
pressure of the blood.

Repeated and sudden raising of the arterial tension, as a result, for
example, of violent muscular efforts or of excessive indulgence in
alcohol, plays an important part in the causation of aneurysm. These
factors probably explain the comparative frequency of aneurysm in those
who follow such arduous occupations as soldiers, sailors,
dock-labourers, and navvies. In these classes the condition usually
manifests itself between the ages of thirty and fifty--that is, when the
vessels are beginning to degenerate, although the heart is still
vigorous and the men are hard at work. The comparative immunity of women
may also be explained by the less severe muscular strain involved by
their occupations and recreations.

S