Treatment.—­When there is evidence that gangrene has occurred, the first indication is to prevent infection by purifying the part, and after careful drying to wrap it in a thick layer of absorbent and antiseptic wool, retained in place by a loosely applied bandage.  A slight degree of elevation of the limb is an advantage, but it must not be sufficient to diminish the amount of blood entering the part.  Hot-bottles are to be used with the utmost caution.  As absolute dryness is essential, ointments or other greasy dressings are to be avoided, as they tend to prevent evaporation from the skin.  Opium should be given freely to alleviate pain.  Stimulation is to be avoided, and the patient should be carefully dieted.

When the gangrene is limited to the toes in old and feeble patients, some surgeons advocate the expectant method of treatment, waiting for a line of demarcation to form and allowing the dead part to be separated.  This takes place so slowly, however, that it necessitates the patient being laid up for many weeks, or even months; and we agree with the majority in advising early amputation.

In this connection it is worthy of note that there are certain points at which gangrene naturally tends to become arrested—­namely, at the highly vascular areas in the neighbourhood of joints.  Thus gangrene of the great toe often stops when it reaches the metatarso-phalangeal joint; or if it trespasses this limit it may be arrested either at the tarso-metatarsal or at the ankle joint.  If these be passed, it usually spreads up the leg to just below the knee before signs of arrestment appear.  Further, it is seen from pathological specimens that the spread is greater on the dorsal than on the plantar aspect, and that the death of skin and subcutaneous tissues extends higher than that of bone and muscle.

These facts furnish us with indications as to the seat and method of amputation.  Experience has proved that in senile gangrene of the lower extremity the most reliable and satisfactory results are obtained by amputating in the region of the knee, care being taken to perform the operation so as to leave the prepatellar anastomosis intact by retaining the patella in the anterior flap.  The most satisfactory operation in these cases is Gritti’s supra-condylar amputation.  Haemorrhage is easily controlled by digital pressure, and the use of a tourniquet should be dispensed with, as the constriction of the limb is liable to interfere with the vitality of the flaps.

When the tibial vessels can be felt pulsating at the ankle it may be justifiable, if the patient urgently desires it, to amputate lower than the knee; but there is considerable risk of gangrene recurring in the stump and necessitating a second operation.

That amputation for senile gangrene performed between the ankle and the knee seldom succeeds, is explained by the fact that the vascular obstruction is usually in the upper part of the posterior tibial artery, and the operation is therefore performed through tissues with an inadequate blood supply.  It is not uncommon, indeed, on amputating above the knee, to find even the popliteal artery plugged by a clot.  This should be removed at the amputation by squeezing the vessel from above downward by a “milking” movement, or by “catheterising the artery” with the aid of a cannula with a terminal aperture.