On the other hand, substances may be medically inconsistent, which are chemically compatible, as I shall have frequent opportunities of exemplifying. The stomach has a chemical code of its own, by which the usual affinities of bodies are frequently modified, often suspended, and sometimes entirely subverted; this truth is illustrated in a very striking manner by the interesting experiments of M. Drouard, who found that Copper, swallowed in its metallic state, was not rendered poisonous by meeting with oils, or fatty bodies; nor even with _Vinegar_, in the digestive organs. Other bodies, on the contrary, seem to possess the same habitudes in the stomach as in the laboratory, and are alike influenced in both situations by the chemical action of various bodies, many examples of which are to be found under the consideration of the influence which solubility exerts upon the medicinal activity of substances; so again, acidity in the stomach is neutralized by _Alkalies_, and if a _Carbonate_ be employed for that purpose, we have a copious disengagement of _Carbonic acid gas_, which has been frequently very distressing to the patient; lastly, many bodies taken into the stomach undergo decompositions and changes _in transitu_, independent of any play of chemical affinities from the hidden powers of digestion, some of which we are enabled to appreciate, and they will accordingly form a subject of investigation in the course of the present work. The powers of the stomach would seem to consist in decomposing the _Ingesta_, and reducing them into simpler forms, rather than in complicating them, by favouring new combinations. But every rational physician must feel in its full force, the absurdity of expecting to account for the phænomena of life upon principles deduced from the analogies of inert matter, and we therefore find that the most intelligent physiologists of modern times have been anxious to discourage the attempt, and to deprecate its folly. Sir Gilbert Blane, in his luminous work on MEDICAL LOGIC, when speaking of the different theories of digestion, tells us that Dr. William Hunter, whose peculiar sagacity and precision of mind detected at a glance the hollowness of such delusive hypotheses, and saw the danger which theorists run in trusting themselves on such slippery ground, expressed himself in his public lectures, with that solidity of judgment combined with facetiousness of expression, which rendered him unparalleled as a public teacher. “Gentlemen,” said he, “Physiologists will have it that the stomach is a mill—others, that it is a fermenting-vat—others again, that it is a stew-pan,—but in my view of the matter, it is neither a mill, a fermenting-vat, nor a stew-pan—but a STOMACH, Gentlemen, a STOMACH.”