Now from these circumstances may be learnt the seats and extents of fistulas, and what parts they have damaged. From the quantity of the pus it may be known, whether they be simple, or divided into more parts. If more of that comes away, than can issue from a single cavity, it is evident there are more sinuses. And as flesh, nerves, and some nervous substances, such as the greatest part of the coats and membranes are, commonly lie together, the nature of the pus will discover whether the several sinuses have eaten through these different sorts of bodies. For from flesh a smooth and white pus is discharged pretty copiously; from a nervous place the discharge is of the same colour indeed, but thinner, and less in quantity; from a nerve fat and not unlike to oil. Lastly, the posture of the body also discovers whether the fistulas have penetrated into several parts, because often, when one lies down with his body and limb in a different position, the pus begins to flow again, which had before stopped, and shews not only that there is another sinus, from whence it descends, but also that it proceeds in a different direction. If it be confined to the flesh, and is recent and simple, neither consisting of sinuses, nor having a large cavity: also if it be not in a joint, but in a part, which is immoveable by itself, and is never put in motion but with the whole body, a plaister for recent wounds will be sufficient, if that contain either salt, or allum, or copper scales, or verdigrease, or any of the metallic substances. And of this a collyrium(89) ought to be made, at the one end smaller, and at the other somewhat thicker. And this ought to be introduced with the small end foremost into the fistula, till pure blood begins to appear. This is universal in the application of all collyriums for fistulas. And then the same plaister is to be put over it spread upon linen; and above that must be applied a sponge first dipt in vinegar; and it is sufficient to open the dressings on the fifth day. Such diet must be used, as I have recommended for generating flesh. But if the fistula is at a distance from the præcordia, it is necessary for the patient now and then to eat radishes fasting and then to vomit.