Treatment.—­The first indication is to exclude bacteria by purifying the damaged part and its surroundings, and applying dry, non-irritating dressings.

When these measures are successful, dry gangrene ensues.  The raw surface left after the separation of the dead skin may be allowed to heal by granulation, or may be covered by skin-grafts.  In the case of a finger or a limb it is not necessary to wait until spontaneous separation takes place, as this is often a slow process.  When a well-marked line of demarcation has formed, amputation may be performed just sufficiently far above it to enable suitable flaps to be made.

The end of a stump, after spontaneous separation of the gangrenous portion, requires to be trimmed, sufficient bone being removed to permit of the soft parts coming together.

If moist gangrene supervenes, amputation must be performed without delay, and at a higher level.

#Gangrene from Heat, Chemical Agents, and Cold.#—­Severe #burns# and #scalds# may be followed by necrosis of tissue.  So long as the parts are kept absolutely dry—­as, for example, by the picric acid method of treatment—­the grossly damaged portions of tissue undergo dry gangrene; but when wet or oily dressings are applied and organisms gain access, moist gangrene follows.

Strong #chemical agents#, such as caustic potash, nitric or sulphuric acid, may also induce local tissue necrosis, the general appearances of the lesions produced being like those of severe burns.  The resulting sloughs are slow to separate, and leave deep punched-out cavities which are long of healing.

#Carbolic Gangrene.#—­Carbolic acid, even in comparatively weak solution, is liable to induce dry gangrene when applied as a fomentation to a finger, especially in women and children.  Thrombosis occurs in the blood vessels of the part, which at first is pale and soft, but later becomes dark and leathery.  On account of the anaesthetic action of carbolic acid, the onset of the process is painless, and the patient does not realise his danger.  A line of demarcation soon forms, but the dead part separates very slowly.

#Gangrene from Frost-bite.#—­It is difficult to draw the line between the third degree of chilblain and the milder forms of true frost-bite; the difference is merely one of degree.  Frost-bite affects chiefly the toes and fingers—­especially the great toe and the little finger—­the ears, and the nose.  In this country it is seldom seen except in members of the tramp class, who, in addition to being exposed to cold by sleeping in the open air, are ill-fed and generally debilitated.  The condition usually manifests itself after the parts, having been subjected to extreme cold, are brought into warm surroundings.  The first symptom is numbness in the part, followed by a sense of weight, tingling, and finally by complete loss of sensation.  The part attacked becomes white and bleached-looking, feels icy cold, and is insensitive to touch.  Either immediately, or, it may be, not for several days, it becomes discoloured and swollen, and finally contracts and shrivels.  Above the dead area the limb may be the seat of excruciating pain.  The dead portion is cast off, as in other forms of dry gangrene, by the formation of a line of demarcation.