[56] These acids coagulate the pus, and thus afford an artificial covering, or film, which remains in close contact with the granulations, and thus, by producing the natural circumstance of contact and covering, the effects of which have been already mentioned, as well as by creating a more vigorous action by their specific action, they frequently bring those sores into a healthy state. Infusion of Cayenne pepper, in vinegar, added to water, in such a quantity as to smart, forms also a very useful application. Of all these remedies, the ointments composed of the nitro-metallic salts, particularly the mercurial, are most generally useful: And the cure seems to be accelerated, by applying cloths dipped in weak solution of metallic salts, or weak acids, during the intervals of dressing. Whenever these applications fail, they must be dropped: And those which fail first, and soonest, seem to be the watery, or fluid applications; and, next to these, the simple resinous ointments. These remedies generally produce their effect first at the margins. When this takes place, we must diminish the strength of the application at that part, in proportion to the activity of the action, which is marked by the redness and pointedness of the granulation, and the cicatrizing state. The circumference, and the rest of the surface, must, in this case, be dressed with different strips of linen, spread with different ointments. Soft linen, spread with simple cerate, or dry lint, which is preferable, should be applied to the cicatrix, and cicatrizing granulations, whilst a stimulating substance is applying to the rest of the surface. When the surface is obstinately diseased, or the action very torpid and imperfect, caustic has been applied; but, although I have often used it, and even applied cloths dipped in solutions of metallic salts, so strong as to form an universal eschar, or slough, yet no benefit whatever was derived; for we do not thus change the nature of the action, but only remove a layer of the surface, and leave that below in possession of the same mode of action with the former. Caustic is more useful, when applied to callus edges; but even these are more effectually removed, by remedies which act more permanently, and gradually, particularly by pressure. The ancients used to extirpate these with the knife, but few will consent to its use. It is indeed more speedy and effectual than the caustic; but, unless the action be afterwards properly supported, it will be of no permanent service. The hard and thickened state of the surrounding integuments, in old ulcers, is best moderated by pressure; but this must be long continued.