Magnesia, calcined Magnesia, chalk, crab's eyes, _pulv. e chel. cancr. c._ and _pulv. contrayerv. comp._ each in the proportion of two scruples to two drachms of ox gall and two ounces of water, were exposed to the usual warmth. The crab's eyes mixture grew rank in twenty-four hours, and in forty-eight was absolutely putrid: the bile with the chalk was in the same condition in twelve hours more. The Magnesia mixture became putrid on the ninth day; the _pulvis e chel._[s] on the tenth; but the _pulvis contrayerv. comp._ preserved the bile from corruption about three weeks, and no change was perceptible in that with the calcined Magnesia when examined above a month after their first admixture. [s] Doctor Macbride found that _pulv. e chel. c. c._ hastened the corruption of bile: might not this depend on some variety in the composition of that powder? Chalk and oyster shells are often substituted in the hospitals and by the druggists, for the other ingredients. EXPERIMENT IX. Twenty grains of Magnesia, and the same quantity of chalk, were separately neutralized with distilled vinegar, and their effects on ox gall compared with that of thirty grains of the artificial Epsom salt dissolved in a sufficient quantity of water. The bile in this solution became putrid in about sixty hours. That in the solutions made in the vegetable acid retained its sweetness for several days longer. These experiments, which terminated so very differently from what I had expected, seem to justify, in some degree, the practice of giving the testaceous and absorbent medicines in fevers of a putrescent type, at the same time that they point out some of that class which ought to be avoided, and evince how fallacious a method it is to judge of the effects of medicines _a priori_. As the bile is, by many, supposed to be the great source of putrid diseases, ought not the antiseptics which may be prescribed in these cases, to be such as more particularly impede the corruption of this fluid, rather than that of flesh? On account of the superiour antisepticity of the calcined Magnesia to most of the absorbents, and its greater purity and solubility, together with the probability of its acting as an evacuant, as well as a corrector of putrid bile, does it not appear to merit a preference to all other medicines of this class? In diseases where an acid cacochymy prevails, and an alkalescent diet, such as wild fowl, fish, &c. is prescribed, but from the scarcity of these articles in some countries, cannot be complied with; may not taking Magnesia or the testaceous powders, immediately before or after meal time, coincide with this intention, by increasing the putrefactive fermentation of other animal food in the stomach, which in these disorders is almost totally subdued by the superabundant acid?