, are liable to be followed by the formation of an
aneurysm.

When, however, the incision in the vessel wall is oblique or transverse,
the retraction of the muscular coat causes the opening to gape, with the
result that there is haemorrhage, which, even in comparatively small
arteries, may be so profuse as to prove dangerous. When the associated
wound in the soft parts is valvular the haemorrhage is arrested and an
aneurysm may develop.

When a large arterial trunk, such as the external iliac, the femoral,
the common carotid, the brachial, or the popliteal, has been partly
divided, for example, in the course of an operation, the opening should
be closed with sutures--_arteriorrhaphy_. The circulation being
controlled by a tourniquet, or the artery itself occluded by a clamp,
fine silk or catgut stitches are passed through the outer and middle
coats after the method of Lembert, a fine, round needle being employed.
The sheath of the vessel or an adjacent fascia should be stitched
over the line of suture in the vessel wall. If infection be excluded,
there is little risk of thrombosis or secondary haemorrhage; and even if
thrombosis should develop at the point of suture, the artery is
obstructed gradually, and the establishment of a collateral circulation
takes place better than after ligation. In the case of smaller trunks,
or when suture is impracticable, the artery should be tied above and
below the opening, and divided between the ligatures.

#Gunshot Wounds of Blood Vessels.#--In the majority of cases injuries of
large vessels are associated with an external wound; the profusion of
the bleeding indicates the size of the damaged vessel, and the colour of
the blood and the nature of the flow denote whether an artery or a vein
is implicated.

When an artery is wounded a firm _haematoma_ may form, with an expansile
pulsation and a palpable thrill--whether such a haematoma remains
circumscribed or becomes diffuse depends upon the density or laxity of
the tissues around it. In course of time a _traumatic arterial aneurysm_
may develop from such a haematoma.

When an artery and its companion vein are injured simultaneously an
_arterio-venous aneurysm_ (p. 310) may develop. This frequently takes
place without the formation of a haematoma as the arterial blood finds
its way into the vein and so does not escape into the tissues. Even if a
haematoma forms it seldom assumes a great size. In time a swelling is
recognised, wit