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, with 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.