produce, by the local application of a purgative salt to the serous surface of the intestine, a striking increase in peristalsis, and to suppress these movements by a similar application of solutions of calcium, magnesium, or strontium chloride_. These experiments also seem to decide the question as to whether the salt solutions act after being absorbed into the blood or only when placed in the intestine. According to Hay[33] and others, the salt which is absorbed into the circulation has no effect and the only action is produced by that which remains in the intestine. This is obviously not true since the solutions act much more rapidly and more powerfully when applied to the outside of the intestine, _i.e._, to the peritoneal surface. No action is observed until after an interval of 10 to 15 minutes after the salt solution is placed in the lumen of the intestine, while application of the same solution to the peritoneal surface causes movements of the intestine within one minute. FOOTNOTES: [31] Pohl (Arch. f. exp. Path. u. Pharm., Bd. 34, S. 87) stated that all sodium and ammonium salts increased the peristalsis when applied to the peritoneal surface of the intestine. [32] MACCALLUM, J. B.: Amer. Journ. Physiol., Vol. X, No. V, 1904, p. 259. [33] _Loc. cit._ CHAPTER IV. The Production of Increased Secretion of Fluid into the Intestine by the Saline Purgatives. One of the most characteristic things to be observed in purgation is the presence of a greater quantity of fluid in the stools. This varies in degree with the different drugs, but even with the mild laxatives the faeces become less solid. With the stronger purgatives they become quite fluid. Since the earliest attempts to explain the nature of purgation there has been the question as to the origin of this fluid. With the discovery of the property of osmosis in salts a new life was given to this inquiry, and Poiseuille[34] advanced the theory that the purgative effect of salts was due entirely to their endosmotic power, the increased fluid of the faeces being caused by the extraction of fluid from the tissues by the osmotic power of the salt. The same view was held by Liebig,[35] whose name is commonly associated with the hypothesis. Rabuteau[36] later on supported this idea and claimed as proof of it the fact that he was unable to produce purgation by the intravenous injection of large quantities of sodium sulphate. He even found that this injection caused constipation, and he concluded that since sodium sulphate purges when given by mouth there must be caused a flow of fluid towards the salt in both cases. This osmosis theory was attacked by Claude Bernard,[37] who pointed out that if the purgative action of salts were due to their osmotic power, sugar must also be a strong purgative. He found further that, contrary to what Rabuteau stated, intravenous injections of sodium sulphate do