g the muscle fibres in concentric rings.

The primary cause of arterio-sclerosis is not definitely known, but its
almost constant occurrence, to a greater or less degree, in the aged
suggests that it is of the nature of a senile degeneration. It is
favoured by anything which throws excessive strain on the vessel walls,
such as heavy muscular work; by chronic alcoholism and syphilis; or by
such general diseases as tend to raise the blood-pressure--for example,
chronic Bright's disease or gout. It occurs with greater frequency and
with greater severity in men than in women.

Atheromatous degeneration is most common in the large arterial trunks,
and the changes are most marked at the arch of the aorta, opposite the
flexures of joints, at the mouths of large branches, and at parts where
the vessel lies in contact with bone. The presence of diseased patches
in the wall of an artery diminishes its elasticity and favours
aneurysmal dilatation. Such a vessel also is liable to be ruptured by
external violence and so give rise to traumatic aneurysm. Thrombosis is
liable to occur when calcareous plates are exposed in the lumen of the
vessel by destruction of the endothelium, and this predisposes to
embolism. Arterio-sclerosis also interferes with the natural arrest of
haemorrhage, and by rendering the vessels brittle, makes it difficult to
secure them by ligature. In advanced cases the accessible arteries--such
as the radial, the temporal or the femoral--may be felt as firm,
tortuous cords, which are sometimes so hard that they have been aptly
compared to "pipe-stems." The pulse is smaller and less compressible
than normal, and the vessel moves bodily with each pulsation. It must be
borne in mind, however, that the condition of the radial artery may fail
to afford a clue to that of the larger arteries. Calcified arteries are
readily identified in skiagrams (Fig. 65).

[Illustration: FIG. 65.--Radiogram showing Calcareous Degeneration
(Atheroma) of Arteries.]

We have met with a chronic form of arterial degeneration in elderly
women, affecting especially the great vessels at the root of the neck,
in which the artery is remarkably attenuated and dilated, and so friable
that the wall readily tears when seized with an artery-forceps,
rendering ligation of the vessel in the ordinary way well-nigh
impossible. Matas suggests infolding the wall of the vessel with
interrupted sutures that do not pierce the intima, and wrapping it
round