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 seldo