Actuarius, in like manner, briefly directs that unless the sinus open downwards, it shall be cut open and dressed with an agglutinative application. You may think well of the case, he adds, when the part is dry and free from pain, or when only a little well-concocted pus is discharged from it. In the translations of the Arabians, the sinus is described by the names of _absconsio_ and _caverna_. Avicenna states that the sinus differs from the fistula in having a larger cavity, and its edges not being indurated. He lays down very correct rules of treatment, but they are all copied from Galen. Thus he directs, when the orifice of the sore is above the cavity of the sinus, that it should be cut open; or, if this cannot be conveniently accomplished, he recommends us to introduce a tent smeared with some incarnant or detergent application. Upon the authority of Dioscorides he recommends the lesser centaury in such cases. His directions for the application of the bandages are similar to those of our author. Celsus, and other of the ancient authorities, do not treat of the sinus separately from the fistula. SECT. XLIX.—ON FISTULA. Fistula is a callous sinus formed for the most part from abscesses, and deriving its appellation from the pipes of reeds (fistulæ). If, therefore, it terminate with a bone, it cannot be cured without a surgical operation, unless in process of time a scale of the bone come off spontaneously. But if it does not terminate with a bone, it is to be cured by the applications for removing callosities, and the agglutinative medicines. The applications for removing callosities are such as these: the root of spondylium scraped around and applied removes the callus of fistulæ. And in like manner black hellebore applied removes the callus in two or three days; also lees of oil boiled and injected; sori in a crude state, or burnt and injected with some diluted wine, or sori and crocomagma with hydromel. Or make collyria by mixing elaterium with turpentine, and apply. Or syringe with the juice of the root of laserwort. This melts down the callus: of verdigris, dr. xij; of ammoniac, dr. ij; mix with vinegar, and form into an oblong collyrium.