In the former method such drugs as perchloride of mercury in the lump, or nitrate of silver, chloride of zinc, and caustic potash or soda in the stick, are introduced into each of the sinuses present. This is done by means of a director or a probe. A better method, however, when the dressing lends itself to the purpose, is to use it in the form of a powder, wrapped in the form of small cubes in extremely thin paper, such, for instance, as is used for rolling cigarettes. It is then conveniently inserted into each fistula. Introduced in this more finely divided form the drug is, perhaps, a little more active in bringing about the desired result. This method of 'plugging,' although practised by many, we cannot recommend in preference to the use of the hot iron or of liquid injections. Our reasons are these: the action of the drug is a protracted one. Almost immediately after its introduction into the fistula there is formed about it an almost impermeable layer of a metallic albuminate, which effectively prevents further rapid action of the caustic. In addition to thus preventing further action of the dressing, this combination of the tissue albumin with the metal of the salt, together with much necrotic tissue that it has caused, is extremely hard to remove from the healthy tissues. This we explain by pointing out that the action of the caustic, prolonged as it is, sets up a tissue reaction which partakes largely of the type of a chronic rather than an acute inflammation. With a chronic inflammation there is sooner a tendency to the production of fibrous tissue (and thus the firmer attachment of the necrosed portions) rather than an active phagocytosis and the casting-off of a slough. Again, careful though we may be with the probe, it is extremely difficult to be certain that we have discovered the whole extent of any fistula. An equal difficulty, therefore, exists in being certain that we have placed the caustic in the position in which it is most wanted--namely, at the furthermost end of the fistula where the necrotic tissue is to be found. When a caustic is used at all, it is far better to employ it in the liquid form, when either of the drugs we have just mentioned may again be used. In the first place, the liquid is far more likely to be brought into contact with the diseased structures than is the solid salt. Also, its action may be regulated by altering the strength of the solution, and the liability to form impermeable albuminates thus diminished. Probably the best solution for use in this way is the old-fashioned Villate's solution (see p. 199). This liquid should be injected at least every day, and, in a bad case, even two or three times daily. Practical hints to be borne in mind when attempting to cure quittor by means of injections are these: If the fistulas are numerous, the fluid should be injected into their various orifices.