h a palpable thrill and a systolic bruit, loudest at the
level of the communication and accompanied by a continuous venous hum.

If leakage occurs into the tissues, the extravasated blood may occlude
the vein by pressure, and the symptoms of arterial aneurysm replace
those of the arterio-venous form, the systolic bruit persisting, while
the venous hum disappears.

_Gangrene_ may ensue if the blood supply is seriously interfered with,
or the signs of _ischaemia_ may develop; the muscles lose their
elasticity, become hard and paralysed, and anaesthesia of the "glove" or
"stocking" type, with other alterations of sensation ensue. Apart from
ischaemia, _reflex paralysis_ of motion and sensation of a transient kind
may follow injury of a large vessel.

_Treatment_ is carried out on the same lines as for similar injuries due
to other causes.

INJURIES OF VEINS

Veins are subject to the same forms of injury as arteries, and the
results are alike in both, such variations as occur being dependent
partly on the difference in their anatomical structure, and partly on
the conditions of the circulation through them.

#Subcutaneous rupture# of veins occur most frequently in association
with fractures and in the reduction of dislocations. The veins most
commonly ruptured are the popliteal, the axillary, the femoral, and the
subclavian. On account of the smaller amount of elastic and muscular
tissue in the wall of a vein, the contraction and retraction of its
walls are less than in an artery, and so bleeding may continue for a
longer period. On the other hand, owing to the lower blood-pressure the
outflow goes on more slowly, and the gradually increasing pressure
produced by the extravasated blood is usually sufficient to arrest the
haemorrhage before it becomes serious. As an aid in diagnosing the source
of the bleeding, it should be remembered that the rupture of a vein does
not affect the pulsation in the limb beyond. The risks are practically
the same as when an artery is ruptured, excepting that of aneurysm, and
the treatment is carried out on the same lines, but it is seldom
necessary to operate for the purpose of applying a ligature to the
injured vein.

#Wounds# of veins--punctured and incised--frequently occur in the course
of operations; for example, in the removal of tumours or diseased glands
from the neck, the axilla, or the groin. They are also met with as a
result of accidental stabs and of suicidal or homicida