To prevent the occurrence of gangrene from frost-bite it is necessary to avoid the sudden application of heat.  The patient should be placed in a cold room, and the part rubbed with snow, or put in a cold bath, and have light friction applied to it.  As the circulation is restored the general surroundings and the local applications are gradually made warmer.  Elevation of the part, wrapping it in cotton wool, and removal to a warmer room, are then permissible, and stimulants and warm drinks may be given with caution.  When by these means the occurrence of gangrene is averted, recovery ensues, its onset being indicated by the white parts assuming a livid red hue and becoming the seat of an acute burning sensation.

A condition known as Trench feet was widely prevalent amongst the troops in France during the European War.  Although allied to frost-bite, cold appears to play a less important part in its causation than humidity and constriction of the limbs producing ischaemia of the feet.  Changes were found in the endothelium of the blood vessels, the axis cylinders of nerves, and the muscles.  The condition does not occur in civil life.

#Diabetic Gangrene.#—­This form of gangrene is prone to occur in persons over fifty years of age who suffer from glycosuria.  The arteries are often markedly diseased.  In some cases the existence of the glycosuria is unsuspected before the onset of the gangrene, and it is only on examining the urine that the cause of the condition is discovered.  The gangrenous process seldom begins as suddenly as that associated with embolism, and, like senile gangrene, which it may closely simulate in its early stages, it not infrequently begins after a slight injury to one of the toes.  It but rarely, however, assumes the dry, shrivelling type, as a rule being attended with swelling, oedema, and dusky redness of the foot, and severe pain.  According to Paget, the dead part remains warm longer than in other forms of senile gangrene; there is a greater tendency for patches of skin at some distance from the primary seat of disease to become gangrenous, and for the death of tissue to extend upwards in the subcutaneous planes, leaving the overlying skin unaffected.  The low vitality of the tissues favours the growth of bacteria, and if these gain access, the gangrene assumes the characters of the moist type and spreads rapidly.

The rules for amputation are the same as those governing the treatment of senile gangrene, the level at which the limb is removed depending upon whether the gangrene is of the dry or moist type.  The general treatment for diabetes must, of course, be employed whether amputation is performed or not.  Paget recommended that the dietetic treatment should not be so rigid as in uncomplicated diabetes, and that opium should be given freely.

The prognosis even after amputation is unfavourable.  In many cases the patient dies with symptoms of diabetic coma within a few days of the operation; or, if he survives this, he may eventually succumb to diabetes.  In others there is sloughing of the flaps and death results from toxaemia.  Occasionally the other limb becomes gangrenous.  On the other hand, the glycosuria may diminish or may even disappear after amputation.