Complete Subcutaneous Rupture.—­When the rupture is complete, all the coats of the vessel are torn and the blood escapes into the surrounding tissues.  If the original injury is attended with much shock, the bleeding may not take place until the period of reaction.  Rupture of the popliteal artery in association with fracture of the femur, or of the axillary or brachial artery with fracture of the humerus or dislocation of the shoulder, are familiar examples of this injury.

Like incomplete rupture, this lesion is accompanied by loss of pulsation and power, and by coldness of the limb beyond; a tense and excessively painful swelling rapidly appears in the region of the injury, and, where the cellular tissue is loose, may attain a considerable size.  The pressure of the effused blood occludes the veins and leads to congestion and oedema of the limb beyond.  The interference with the circulation, and the damage to the tissues, may be so great that gangrene ensues.

Treatment.—­When an artery has been contused or ruptured, the limb must be placed in the most favourable condition for restoration of the circulation.  The skin is disinfected and the limb wrapped in cotton wool to conserve its heat, and elevated to such an extent as to promote the venous return without at the same time interfering with the inflow of blood.  A careful watch must be kept on the state of nutrition of the limb, lest gangrene occurs.

If no complications supervene, the swelling subsides, and recovery may be complete in six or eight weeks.  If the extravasation is great and the skin threatens to give way, or if the vitality of the limb is seriously endangered, it is advisable to expose the injured vessel, and, after clearing away the clots, to attempt to suture the rent in the artery, or, if torn across, to join the ends after paring the bruised edges.  If this is impracticable, a ligature is applied above and below the rupture.  If gangrene ensues, amputation must be performed.

These descriptions apply to the larger arteries of the extremities.  A good illustration of subcutaneous rupture of the arteries of the head is afforded by the tearing of the middle meningeal artery caused by the application of blunt violence to the skull; and of the arteries of the trunk—­caused by the tearing of the renal artery in rupture of the kidney.

#Open Wounds of Arteries—­Laceration.#—­Laceration of large arteries is a common complication of machinery and railway accidents.  The violence being usually of a tearing, twisting, or crushing nature, such injuries are seldom associated with much haemorrhage, as torn or crushed vessels quickly become occluded by contraction and retraction of their coats and by the formation of a clot.  A whole limb even may be avulsed from the body with comparatively little loss of blood.  The risk in such cases is secondary haemorrhage resulting from pyogenic infection.

The treatment is that applicable to all wounds, with, in addition, the ligation of the lacerated vessels.