=Operation.= The instruments necessary are: a Sims’s or Auvard’s (Fig. 37) speculum; two flat spatulæ; three long-handled knives (Fig. 38), one with a long haft and a short straight narrow blade, and the others with angular blades (right and left); two long-handled, sharp-pointed, curved scissors (right and left); an Emmett’s hook for making counter-pressure (Fig. 40); toothed forceps (Fig. 39) and tenaculum; six Spencer Wells’s forceps; Schauta’s needle-holder (Fig. 73) with short curved needles. [Illustration: FIG. 41. SIMS’S OPERATION FOR THE REPAIR OF A VESICO-VAGINAL FISTULA. _a._ Bladder mucous membrane. _b._ Vaginal wall. _c._ Suture passed but not tied. _d._ Section of denuded surface. _e, e_{1}._ Liberating incisions. _f._ The fistula. ] The patient is placed in the lithotomy position. A strip of mucous membrane is then removed from the whole of the vaginal edge of the fistula by means of an angular knife. In the original operation Sims (Fig. 41) made the surface oblique, but Simon (Fig. 42) considered the raw surface should be at right angles to the mucous membrane. The blade of the knife should not wound the vesical mucous membrane. After the bleeding has ceased, the sutures, which may be of silk or catgut, are passed by means of the needle through the pared edge of the fistula on one side, passing across the fistula, and piercing the raw surface on the opposite side. The entry of the needle should be made about 1/4-1/3 of an inch from the raw edge (Fig. 44). Emmett’s hook, shaped like a button-hook, is useful to produce counter-pressure against the needle point. The sutures are tied, and milk is injected into the bladder to test the accuracy of the union. As a rule, fistulæ are bounded by rather scanty and inelastic walls, owing to the presence of cicatricial tissue; it is therefore more advantageous not to remove any tissue in order to produce a raw surface, or as little as possible. To fulfil this condition, the method of _dédoublement_ or flap-splitting, as practised by Walcher, may be carried out (Fig. 43, A, B, and C). [Illustration: FIG. 42. SIMON’S OPERATION FOR THE REPAIR OF A VESICO-VAGINAL FISTULA. Letters as in the preceding figure.] The patient is placed, as before, in the lithotomy position, and the cervix is pulled down, while the edges of the fistula are kept steady by a volsella on either side. The margin of the orifice is then split all round to a depth of from a quarter to half an inch. Vesical and vaginal mucous membrane flaps are thus produced, giving a large raw surface without any loss of substance. The sutures are passed as shown in Fig. 43, C. =After-treatment.= This is very simple: if the patient is able, she should pass water, either in the dorsal or genu-pectoral position, otherwise a catheter should be passed every six hours. _Modifications of this operation_ have been devised, more especially for the larger fistulæ: they will be briefly mentioned.