The subject of this Proposition divides itself naturally into three parts. We shall have to consider--1. What is the nature, and what the function, of the gastric and intestinal secretions. 2. The laws of this process of Endosmotic absorption, and how they are fulfilled in this case; and, 3. The mode in which the great majority of medicines are reduced to a state of solution, which is necessary before they can be absorbed. The process of stomach-digestion has been cleared up of late years by the decisive experiments of Spallanzani and Réaumur, of Tiedemann and Gmelin, and of Dr. Beaumont of Canada. Immediately that a substance touches the mucous surface of the stomach it causes the copious outpouring of a thin fluid, which is secreted by a glandular apparatus. This gastric juice is highly acid, and contains besides a peculiar nitrogenous substance called Pepsin. Dr. Prout thought that the reaction was due to free Hydrochloric acid. But it seems more likely that it is due to Lactic acid. Such at least is the opinion entertained both by Liebig and Lehmann. Now the result of the action of this fluid is to dissolve down the solid materials of the food, or other substances presented to it, reducing them to a thin watery pulp. This pulp is then mainly absorbed; and that which is not taken up through the coat of the stomach is absorbed in the earlier portion of the intestinal canal. I shall have to treat of Aliments as one of the orders of Restorative Hæmatics. We are now concerned with medicines in general. The same juice is poured out to receive them. Such as are dissolved by it are immediately absorbed. Some other matters may be rendered soluble by the agency of the Bile and Pancreatic juice which are poured out into the middle of the Duodenum. The former is an alkaline fluid, containing carbonate of Soda. The Pancreatic juice is also said to be alkaline. That the stomach is absorbent may be proved by the experiment of placing a ligature round the intestine of a dog, just below the pylorus. It is then found that soluble substances placed in the stomach pass rapidly from it into the circulation. It is probable that all substances which are easily dissolved pass through the coats of the stomach. That the surface of the intestines is absorbent may be proved by the disappearance of enemata thrown into them. Liebig states that a solution of common salt, in the proportion of one part to eighty of water, disappeared so completely in the rectum that an evacuation one hour afterwards was found to contain no more than the usual proportion of salt. (_Animal Chemistry_, _p._ 77.)