This method of treatment is particularly applicable to cases of chronic sub-horny quittor in the more posterior parts of the foot.  Here, if one or more fistulas exist, their openings are probed and the direction of the sinuses determined.  In all probability they are burrowing down along-side the wall to the sole, where, for want of outlet, they are invading the substance of the plantar cushion or the plantar aponeurosis.

Should this preliminary probing demonstrate that neither of the fistulas run dangerously near the joint, then the operation may be decided on.

The animal is cast and chloroformed, the foot firmly fixed, and the horn of the quarter rasped away quite thin.  The sole of the same side is also pared with the knife until the horn of both the quarter and the sole yields easily to pressure of the thumb.  All that is then needed is three or four long, round, and pointed irons (about 1/4 to 3/8 inch in diameter) heated to redness.  These are inserted into the fistulas, and the false mucous coat of these passages thus destroyed.  When the iron, on being directed into the fistulous opening at the coronet, is found to travel alongside the wall, and to easily reach the sole, it should be made to go further still.  The sole is penetrated, and a dependent opening thus made for the escape of the discharge that afterwards accumulates.

What happens now, of course, is that an intense and acute inflammation is set up along the whole track of the fistula, in which position the inflammatory changes were heretofore chronic.  The whole lining of the fistula, and with it, we hope, all necrotic tissue, is cast as a slough, leaving nothing but healthy tissue behind.  This, with a suitable dressing, heals and gives no further trouble.

The after-treatment consists in the application of hot poultices.  These tend to greatly ease the pain, and at the same time to facilitate the removal of the slough.  The poulticing should be continued, therefore, until the sloughing comes about, which happens, as a rule, at about the fifth or seventh day.

Immediately the slough is cast off, the poultices may be discontinued and dressing of the wound carried out.  This consists of injections of solutions of zinc chloride 1 in 200, perchloride of mercury 1 in 1,000, carbolic acid 1 in 20, of Villate’s solution, or of such other antiseptic as the surgeon may think fit.  The dependent orifice at the sole should be kept open for as long as possible, being occasionally trimmed round with the drawing-knife, and scooped out with a sharp-edged director.

Directly a healthy and pink-looking granulation is observed along the track of the iron, and the discharge therefrom takes on a thick and yellow appearance, the strength of the antiseptic solutions should be gradually diminished.  This point, in fact, is of great importance in treating all wounds of the foot.  There is a great temptation, on account of the known excessive liability of the parts to septic infection, to use an antiseptic solution unduly strong.  What must be remembered is that used too strong they themselves give rise to dead tissue, or to impermeable layers consisting of compounds of the discharges with themselves, and so create substances that prove a source of irritation and subsequent trouble.