This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol1", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
There is sufficient ground, in the different properties exercised by the different mineral tonics, for arranging them in three subdivisions; one, including those which, so far as their pure and direct tonic action is concerned, operate exclusively on the mucous membrane of the alimentary canal; a second, those which act on the system at large, and produce their effects by a direct influence upon the vital properties of the tissues, without entering necessarily into their composition; and a third, those which, though they may possibly operate in the mode just mentioned, are nevertheless peculiarly characterized by forming an essential element of some constituent of the body, and produce their remedial effects.
Either by increasing the amount of this constituent, or restoring it when diseased to its normal state by supplying a wanting ingredient. In the first subdivision may be ranked the mineral acids, as the sulphuric, nitric, muriatic, and phosphoric; in the second, the preparations of silver, copper, zinc, and bismuth; and in the third, the preparations of iron.