For the purpose of obviating these very unsatisfactory and highly objectionable results, we have a choice of any one, or all of three different methods, viz: treatment by injection, treatment with the fistulatome, and treatment by the galvano-cautery as practiced by Dr. Shotwell; who, fully appreciating the dangers of muscular section, has hit upon a plan both new and commendable. [Illustration: FIG. 14.—Varieties of Fistula. (Gosselin.)] The sub-cutaneous, or sub-mucous fistula can be cocainized and slit up with a pair of scissors, and the tract cleansed and cauterized with a solution of carbolic acid, a comparatively trivial affair; but the external blind, the internal blind, the complete, the complete with diverticula etc., are varieties which call forth a decidedly greater amount of ingenuity and thought in bringing them to a successful issue. The treatment by injection, sometimes classified as a “non-operative method,” has been so successful in the hands of many, that it is stoutly affirmed that any case curable by the usual heroic methods is equally curable by this method. Different preparations have been used, chief of all being carbolic acid, ranging in strength from 50 per cent. up. In adopting the carbolic acid treatment, probably the better way after preparing the sinus, will be to use a 95 per cent. the first time and subsequently a 50 per cent. solution; protecting the parts from excoriation by any suitable unguent and absorbent cotton. Hot water compresses to relieve pain and reduce swelling. Iodoform, Eucalyptol, etc., in the _interim_. Judgment will be required in not making too many irritant applications and granulation thus hindered for want of rest. The object is to destroy the pyogenic membrane by the cauterizing effects of the acid and get up a granulating carbolic acid sore. It may be necessary to evacuate the bowels and constipate for several days to give the muscles rest, or resort in extreme cases to divulsion. The sinus must have constant, free external drainage until the healing process is complete. Allingham recommends the introduction of the small end of a bone collar button to keep the orifice open, with a hole drilled through its centre for drainage. As a preliminary step the external orifice should be dilated with a laminaria tent or other appropriate means. The fistulous tract explored with a common probe and thoroughly cleansed with hot water introduced through a flexible silver canula; which is also used for the injection of a 5 or 10 per cent. solution of cocaine to obtund the sensibility. [Illustration: FIG. 15.—Bone Stud]