hich the treatment
referred to has been followed by such an amount of improvement that the
patient has been able to resume a laborious occupation for one or more
years. Christopher Heath found that improvement followed ligation of the
left common carotid in aneurysm of the transverse part of the aortic
arch.

[Illustration: FIG. 74.--Thoracic Aneurysm, threatening to rupture
externally, but prevented from doing so by Macewen's needling. The
needles were left in for forty-eight hours.]

#Abdominal Aneurysm.#--Aneurysm is much less frequent in the abdominal
than in the thoracic aorta. While any of the large branches in the
abdomen may be affected, the most common seats are in the aorta itself,
just above the origin of the coeliac artery and at the bifurcation.

The _clinical features_ vary with the site of the aneurysm and with its
rapidity and direction of growth. A smooth, rounded swelling, which
exhibits expansile pulsation, forms, usually towards the left of the
middle line. It may extend upwards under cover of the ribs, downwards
towards the pelvis, or backward towards the loin. On palpation a
systolic thrill may be detected, but the presence of a murmur is neither
constant nor characteristic. Pain is usually present; it may be
neuralgic in character, or may simulate renal colic. When the aneurysm
presses on the vertebrae and erodes them, the symptoms simulate those of
spinal caries, particularly if, as sometimes happens, symptoms of
compression paraplegia ensue. In its growth the swelling may press upon
and displace the adjacent viscera, and so interfere with their
functions.

The _diagnosis_ has to be made from solid or cystic tumours overlying
the artery; from a "pulsating aorta"; and from spinal caries; much help
is obtained by the use of the X-rays.

The condition usually proves fatal, either by the aneurysm bursting into
the peritoneal cavity, or by slow leakage into the retro-peritoneal
tissue.

The Moore-Corradi method has been successfully employed, access to the
sac having been obtained by opening the abdomen. Ligation of the aorta
has so far been unsuccessful, but in one case operated upon by Keen the
patient survived forty-eight days.

#Innominate aneurysm# may be of the fusiform or of the sacculated
variety, and is frequently associated with pouching of the aorta. It
usually grows upwards and laterally, projecting above the sternum and
right clavicle, which may be eroded or displaced (Fig. 75).