course of my professional practice I have witnessed more than an ordinary share of consumptive cases, and I can confidently state that in the treatment of Hæmopthysis, the styptic properties of _Acetate of lead_ are entirely invalidated by combination with _Alum_,[279] or by its exhibition being accompanied with that of the acidulated _infusion of roses_, or with small doses of _sulphate of magnesia_; and yet, I would ask, whether this practice is not usual and general? The practitioner however cannot be too often reminded that he is not to reject a remedy whose value has been ascertained by experience, merely because it appears to be unchemical: the popular and certainly useful pill, consisting of calomel, rhubarb and soap, may be adduced as an example of this kind. Of the _Mistura Ferri Composita_, I will only say that it is a most valuable combination; and whether it be the product of accident, or the result of philosophical induction, it equally deserves a distinguished place in our list of tonic remedies: but it cannot be denied that many of our esteemed arrangements, which are in apparent contradiction to all the laws of composition, owe their efficacy to the operation of affinities altogether blind and fortuitous. It has been observed that the practice of combining certain vegetable tonics with lime-water, although very common, is in cases where we are desirous to obtain their _astringent_ effects, of very doubtful propriety; for the fact is, that _Tannin_ forms with the alkalies and alkaline earths, compounds that are not soluble in water,[280] and which are therefore probably inefficacious. It may perhaps be said that such an argument cannot avail, because if the astringent matter be even introduced into the stomach in its purest form, it will immediately form an insoluble compound on its contact with _gelatine_.[281] We know so little of the laws of _gastric chemistry_, that it is difficult to learn what changes take place in the animal laboratory; but it would seem probable that the powers of the stomach rather consist in decomposing the ingesta into simple forms, than in complicating them by favoring new combinations; besides which, if such a compound were formed, it would be subsequently decomposed _in transitu_; for the experiments of Sir H. Davy shew that vegetable astringent matter passes through the body unchanged. (_page 82._)