A strong scalpel is now introduced at the coronary opening, with its cutting-edge outwards, and is gradually passed down the opening made by the saw.  In this way the sinus is completely destroyed, and from end to end converted into an open wound.  The parts are then washed in a perchloride of mercury solution, covered with a mixture of powdered iodoform and boracic acid, over which a pledget of carbolized tow is placed, and then a bandage over the whole.  This dressing should be left on three or four days, after which the injury should be treated as an ordinary wound.  In conclusion, the author says:  ’I can safely recommend this line of treatment to any practitioner having an obstinate case under treatment.’

Removal of the Wall and Excision of the Necrotic Tissue.—­This we may term the radical operation for sub-horny quittor, for it is often productive of a successful issue when all other means have failed.  No matter in what position the sinus is, whether at the extreme anterior portion of the coronet, or whether in the region of the heels, it is to be thoroughly opened up.  To do this, the fistula is carefully explored with the probe and a knowledge of its exact dimensions arrived at.  This is carefully noted, and the horn of the wall for some little distance around it then rasped down quite thin.  Immediately over the sinus, and for a short distance on either side of it, the horn is stripped away to the sensitive structures.  The cavity of the fistula is then opened up with a scalpel, and every particle of diseased tissue removed with this instrument and a pair of forceps.  After-dressing consists simply in the application of suitable antiseptics.

When the Complication of Necrosed Tendon or Ligament exists.—­We may take it as an axiom that wherever this exists, whether it is in the extensor pedis, in the lateral ligaments of the joint, or in portions of the flexors, all diseased structures should, where possible, be removed.  This is done either with a scalpel or with a curette.

When septic matter has gained the sheath of the perforans, and the formation of pus therein is indicated by inflammatory swellings in the hollow of the heel, it is sometimes advisable to lay the sheath open for 1 to 2 inches along the course of the tendons.  This, if a fistula is present, may be best done with a blunt-pointed bistoury, or with a cannulated director and a scalpel.  With the pus thus given exit, and an antiseptic dressing regularly applied, the case sometimes ends in rapid resolution.  More often than not, however, it is found that the pus has been liberated too late, and that it has gravitated in the sheath to the extent of affecting the plantar aponeurosis.  Or it may be, of course, that it was in the plantar aponeurosis the disease commenced.  Whichever may have been the case, we have in the hollow of the heel one or more fistulous openings, or an opening we have made ourselves, leading down to a necrosed portion of the terminal expansion of the perforans.