Celsus, De Medicina
W. G. Spencer, Ed.

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17 The powers of medicaments when unmixed having been set out, we have to say how how they may be mixed together, and what are the compositions so made. Now they are mixed in various ways and there is no limit to this, since some simples may be omitted, others added, and when the same ingredients are used the proportion of their weights may be changed. Hence though there are not so very many substances having medicinal powers, there are innumerable kinds of mixtures; and, even if all of them could be included, yet this would be needless. For the same effects are produced by but a few compositions, and to vary these is easy to anyone who knows their powers. Therefore I shall content myself with those I have heard of as the best known. Now in this book I will set forth those compositions which may have been required in the previous treatments or which pertain to those treatment with which I am going shortly to mention here, so that I may bring together at the same time compositions which are more generally used: those that are applicable to a particular disease, or even to a few, I shall mention in their appropriate places. But I wish to make clear in advance that our uncia has the weight[p. 15] of seven denarii, next that I divide one denarius by weight into six parts, namely, sextantes; so that I have in the sextans of a denarius the same weight as the Greeks have in what they call an obolus. That being reduced to our weight, takes the obolus a little more than half a scripulus.

Now emollients and plasters and pastils which the Greeks call trochiscoi, whilst they have much in common, differ in this, that emollients are made chiefly from essences of flowers and even from their shoots, plasters and pastils rather from certain metallic materials: again, the emollients if crushed become quite soft enough; for they are applied over intact skin; the materials out of which plasters and pastils are made are rubbed together laboriously in order that they may not irritate wounds when they are applied to them. But between a plaster and a pastil there is this difference: a plaster must contain some liquefied ingredient, in a pastil only dry materials are used, combined together by a little fluid. Then a plaster is made in this way: dry medicaments[p. 17] are rubbed down separately, then when they have been mixed, either vinegar is dropped in or any other liquid free from fat that is at hand, and these ingredients are rubbed together again. The materials capable of being liquefied are melted all together over the fire, and if there is to be any admixing of oil, it is then poured in. A dry ingredient is even sometimes boiled in oil beforehand: when what should be done separately has been accomplished, all are mixed together. But the making of pastils, on the other hand, is this: dry medicaments which have been rubbed together are mixed by the aid of a liquid free from fat, such as wine or vinegar and the mixture is dried again, and when required for use, dissolved in a liquid of the same kind. Further, a plaster is laid on, a pastil is smeared on, or is mixed with something softer such as a cerate.