us out in confiding in the production of certain chemical effects from their use, we must not forget that much is to be effected by their judicious administration as _vital_ agents: and it will be hereafter my duty to point out the many advantages that may be obtained, by combining in one formula, medicines which individually belong to each class. Independent of any chemical effect, alkaline substances are found by daily experience to allay the morbid irritability of the urinary organs in a manner not yet explained; alkalies may also prove _generally_ serviceable in these disorders, by acting immediately upon the digestive organs, for the disposition of forming calculi is always, more or less, accompanied with the indications of deranged digestion; and it is probable that the first link of the series of actions, which cause this disposition, has its origin in the stomach. The alkaline carbonates are found to answer as effectually as the pure alkalies, and they have the advantage of being less liable to disagree with the stomach. Mr. Hatchett has proposed the carbonate of magnesia, in doses of ℈j to ʒj, as a valuable substitute for alkaline remedies in cases of lithic calculi; but as its insolubility must render its absorption equivocal, the beneficial operation of the substance must principally depend upon its neutralizing any excess of acid in the primæ viæ, and in this way there can be no doubt of its lithonthryptic agency; “but,” says Dr. Marcet, “such is the tendency which the public has to over-rate the utility of a new practice, or to take a mistaken view of its proper application, that there is every reason to believe that the use of magnesia has of late years become a frequent source of evil in calculous complaints.” Lime-water has been also recommended for the purpose of fulfilling the same indications, and as not being liable to produce that irritability of stomach which frequently attends the long continued use of the fixed alkalies; besides which, some chemists have maintained that it exerts a peculiar solvent power over the cementing animal matter of the concretion, and thereby destroys its cohesion.[207]