There are two principles according to which the dosage of simples used in compounding is regulated; i.e. one concerning the simple, and the other concerning the composite medicine itself.
As regards the simple: let that be subdivided into seven cases. First of these cases the strength or weakness of the virtue of the cure. Second: greatness or littleness of its efficacy. Third: nobility or ignobility of its efficacy. Fourth: combining one medicine with another giving ease, or leaving it by itself. Fifth: location of the affected member. Sixth: evil effect of the simple. Seventh: when an item is compounded into a composite medicine which item diminishes the efficacy of the other item contained therein.