But where animal food is used in putrescent diseases, either through necessity, or the obstinacy of the patient, ought not Magnesia, in an uncalcined state, and all the calcareous and testaceous earths to be carefully abstained from? Dr. Percival, in a volume of very ingenious experiments and observations which have been before referred to, has mentioned a physician of his acquaintance, who always observed his stools to be more particularly offensive after having taken Magnesia. Might not this proceed from the action of the Magnesia on the animal food he had eaten; and is it not reasonable to suppose that the effect might have been very different where a vegetable or milk diet had been used, as is generally the case in putrid fevers, and in young children? I know a person whose stools are, in common, very little tinged with bile, who after taking calcined Magnesia, evacuates fæces of a very bilious appearance, though less foetid than usual. It is a fact worthy of observation, that in the experiments which were made with calcined Magnesia and bile, the latter was absorbed by, and had united with the former; and another remarkable circumstance was, that the watery part of all the mixtures which resisted putrefaction, acquired a very pungent, saline taste. CHAP. VII. ON THE SOLVENT QUALITIES OF CALCINED MAGNESIA. Dr. Macbride, whose experimental researches have very justly acquired him a high degree of reputation in the philosophical world, supposes fixed air to be the combining principle of bodies, and has applied this ingenious theory to pharmaceutical improvements. He discovered that lime triturated with resinous gums, promotes their dissolution in water; which, he thinks, is thus enabled to take up the same parts of these substances, as are soluble in spirit of wine. These aqueous tinctures are transparent, not milky like the solutions made with yolk of egg, or gum arabic; but the lime communicates a highly disagreeable taste to them, and the action of lime water, which he used in some instances, is not sufficiently powerful to extract strong tinctures from these bodies. As calcined Magnesia has a great affinity with fixed air, I was desirous of trying whether it would contribute to render resinous substances soluble in water; for being itself insoluble, the solutions would consequently be free from any other impregnation than that of the resins. EXPERIMENT X. Five grains of camphor were rubbed for five minutes with an equal quantity of calcined Magnesia: after the camphor was reduced to powder, it united into a hard concrete with the Magnesia, but immediately dissolved on the addition of a small quantity of distilled water, of which an ounce was mixed with them, and immediately passed through filtering paper. The filtrated liquor was highly impregnated with the camphor. EXPERIMENT XI.