a,
dries up, and the shrivelled brown skin is slowly separated by the
growth of granulation tissue beneath and around it.

Fingers, toes, or even considerable portions of limbs may in the same
way be suddenly destroyed by severe trauma, and undergo mummification.
If organisms gain access, typical moist gangrene may ensue, or changes
similar to those of ordinary post-mortem decomposition may take place.

_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 demarcat