Having mentioned the virtues of the simples, we are next to shew in what manner they are to be mixed, and what compositions are made from them. Now they are mixed variously, and there is no certain method for it, since of similar ingredients some are taken away, and others are added; and though the very same simples are all used, the proportion of their weights may be changed. And therefore though the number of medicinal simples be not so very great, there are innumerable kinds of mixtures; which it would be needless to enumerate, though it were possible: both because the same effects are found within the compass of a few compositions; and because it is easy for any person, who is acquainted with their virtues, to change them. I shall therefore confine myself to the most esteemed. Now in this book I shall give an account of those, which may either have been wanted in the preceding, or are employed in the cures, which I am to treat of, only throwing together these compositions, which are of more general use. Such as are accommodated to one particular disorder, or even to a few, I will insert in their proper places.

But before I proceed, I would have it understood, that in an ounce is contained the weight of seven denarii. Next, that I divide each denarius into six parts, that is sextantes, so that I have the same quantity in the sextans of a denarius, that the Greeks have in their obolus[ DM ]. That being reduced to our weights makes a little more than half a scruple.

Now malagmas, and plaisters, and troches, which the Greeks call trochischi[ DN ], though in many things they are the same, differ in this, that malagmas are chiefly made from flowers, and even their stalks, plaisters and troches are more generally composed of some metallic ingredients. Then malagmas being beat up are abundantly soft: for they are applied, where the skin is unbroken: but those things, of which plaisters and troches are made, are carefully powdered; lest they hurt wounds, when they are laid on. Betwixt a plaister and a troche there is this difference, that a plaister admits of something melted: in a troche there are only dry medicines united by some liquid. Again, a plaister is made in this manner: The dry medicines are powdered by themselves: when they are mixed, vinegar is dropped into them, or any other liquor belonging to the composition, that is not greasy; and they are again rubbed with that. Those things, that are capable of being melted, are melted altogether at the fire; and if any oil is to be in the mixture, it is then poured in. Sometimes too, some one of the dry ingredients is first boiled with oil. When these things are finished, which ought to be done separately, the whole is mixed together into one mass. But the way of making troches is this: The dry medicines being powdered are formed into one body with a liquor not greasy, such as wine or vinegar, and again after being brought to a consistence, grow dry: and when they are to be used, are diluted by a liquor of the same kind. There is also a difference in the manner of using these: for a plaister is simply applied, a troche is rubbed on, or else mixed with something softer than itself, or with cerate.