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. In such cases we ourselves have derived benefit from a regular flushing of the sinuses with a 1 in 2,000 solution of perchloride of mercury, introduced by means of a glass syringe, followed later by flushing in the same manner with a 1 in 40 solution of carbolic acid, the hollow of the heel meanwhile being kept clean with an antiseptic pad and bandage, or by liberal applications of an antiseptic powder. The septic materials are in this way destroyed, and the wound heals without further complication. We must admit, however, that the cure of the lesion is generally at the expense of slight lameness, due, in all probability, to inflammatory tissue adhesions between the flexor perforans and the perforatus, and to a partial destruction of the synovial membrane of the sheath. If, in spite of the antiseptic irrigations, the fistula persists, then nothing remains but to resort to excision of the aponeurosis, as described on p. 222. _When Necrosis of the Lateral Cartilage is present_.--In this case we may at first try the ordinary treatments of poulticing; and blistering, of antiseptic caustic injections, and of plugging. In some cases a cure is effected. Should these fail, however, and we intend to see the finish of our case, then operative measures must be determined on. This means cutting down upon the diseased cartilage, and either removing the necrosed portion, or excising the cartilage in its entirety. The latter method is seldom practised in this country. As it is the most radical of the two, however, we shall describe it here first. _Extirpation of the Lateral Cartilage_.--The operation of extirpating the lateral cartilage is by no means a new one, being introduced, according to Zundel, by the senior Lafosse in 1754. It consisted in removing a portion of the wall by grooving and stripping it, and of excising the exposed cartilage by means of a sage-knife.