In the ‘Euporista’ of the Pseudo-Dioscorides, it is recommended first to dilate the fistula with a piece of sponge, and then to use a stimulant application containing verdigris, ammoniac, &c. Aëtius gives an excellent account of fistula, but it is mostly borrowed from Galen. We can afford room only for a few extracts. When a fistula extends obliquely, nothing can be done without making a free incision, for which purpose he directs us to introduce a sound and cut along it. His directions for examining into the nature of a fistula are such as ample experience alone could have dictated. He seems to be decidedly of opinion that, except in cases of a recent fistula, or when it is not deep-seated, an incision ought always to be made at first; after which applications for removing the callus may be used. When, however, the patient refuses to submit to an operation, and the case is recent, the cure may be attempted by means of escharotics and incarnants, such as verdigris, misy, alum, &c., mixed with frankincense, aloes, and myrrh. Oribasius briefly recommends white hellebore, a mixture of equal parts of verdigris and ammoniac, and a few other such articles, as applications for fistulæ. Scribonius Largus mentions several compound applications containing misy, chalcitis, verdigris, alum, &c. Marcellus gives one consisting of ceruse, ammoniac, and oil. Actuarius gives a brief but distinct account of the nature and treatment of fistula, but it is taken almost entire from our author. Avicenna inculcates that a fistula is only to be cured by a free incision, or by removing the callous sides of it by burning with fire or caustic medicines, such as arsenic, ammoniac, sulphur, the flour of copper, or mercury. This in fact is the sum of the medical practice in such cases. There is nothing particularly interesting in Haly Abbas. Alsaharavius truly states that a diseased bone is the common cause of fistulous ulcers not healing, and inculcates that in this case there can be no hope of recovery until the carious portion be removed. Rhases, upon the authority of the celebrated Antyllus, directs us to use corrosive applications when a fistula cannot be operated upon with the scalpel. He intimates that this is particularly the case when the disease is seated in the groins. The earlier modern surgeons, such as Gulielmus de Saliceto, Arnoldus, Rogerius, Rolandus, and Guy of Cauliac, in imitation of the Arabians, direct fistula to be treated by the application of septics, the actual cautery, or incision. Rogerius recommends a tent spread with quicklime and soap, or with arsenic. Guy of Cauliac, like Avicenna, speaks favorably of sublimed quicksilver or corrosive sublimate. SECT. L.—FOR SORES WHICH BREAK OUT AGAIN.