rm most commonly met with in civil practice. It may follow such
trivial injuries as a pin-prick or a scratch, the signs of acute
cellulitis rapidly giving place to those of a spreading gangrene. Or it
may ensue on a severe railway, machinery, or street accident, when
lacerated and bruised tissues are contaminated with gross dirt. Often
within a few hours of the injury the whole part rapidly becomes painful,
swollen, oedematous, and tense. The skin is at first glazed, and perhaps
paler than normal, but soon assumes a dull red or purplish hue, and
bullae form on the surface. Putrefactive gases may be evolved in the
tissues, and their presence is indicated by emphysematous crackling when
the part is handled. The spread of the disease is so rapid that its
progress is quite visible from hour to hour, and may be traced by the
occurrence of red lines along the course of the lymphatics of the limb.
In the most acute cases the death of the affected part takes place so
rapidly that the local changes indicative of gangrene have not time to
occur, and the fact that the part is dead may be overlooked.

[Illustration: FIG. 22.--Gangrene of Terminal Phalanx of Index-Finger,
following cellulitis of hand resulting from a scratch on the palm of the
hand.]

Rigors may occur, but the temperature is not necessarily raised--indeed,
it is sometimes subnormal. The pulse is small, feeble, rapid, and
irregular. Unless amputation is promptly performed, death usually
follows within thirty-six or forty-eight hours. Even early operation
does not always avert the fatal issue, because the quantity of toxin
absorbed and its extreme virulence are often more than even a robust
subject can outlive.

_Treatment._--Every effort must be made to purify all such wounds as are
contaminated by earth, street dust, stable refuse, or other forms of
gross dirt. Devitalised and contaminated tissue is removed with the
knife or scissors and the wound purified with antiseptics of the
chlorine group or with hydrogen peroxide. If there is a reasonable
prospect that infection has been overcome, the wound may be at once
sutured, but if this is doubtful it is left open and packed or
irrigated.

When acute gangrene has set in no treatment short of amputation is of
any avail, and the sooner this is done, the greater is the hope of
saving the patient. The limb must be amputated well beyond the apparent
limits of the infected area, and stringent precautions must be taken to