To any one making these experiments there can be no doubt that the increased peristalsis is the direct result of the injection of the salt. It can be readily proven in the following way: As will be shown in a later chapter, the peristalsis and secretion caused by the saline purgatives can be inhibited by the administration of calcium or magnesium chloride. If now in a rabbit in which the intestine has been set into active motion by the intravenous injection of sodium citrate, a small quantity of m/6 CaCl_{2} be administered intravenously, all of these movements cease within a minute or two. A second injection of a slightly greater quantity of m/6 sodium citrate will overcome this action and cause active peristalsis to begin again. These actions cannot be due to anything but the solutions introduced. It is evident also in watching the action of these salts that they produce increased peristalsis much more rapidly and powerfully when introduced intravenously than when placed in the lumen of the stomach or intestine. A much smaller dose also is required to produce this effect. They therefore cannot act because of their presence in the lumen of the gut, or because of their being subsequently secreted into the lumen. When introduced into the stomach or intestine they must first be absorbed into the blood before they can reach the muscular and glandular tissues upon which they act. They therefore act more slowly and only in larger quantities when administered in this way. Experiments similar to the above were made with a number of salts, including sodium sulphate, fluoride, tartrate, phosphate and oxalate, barium chloride, and magnesium sulphate. It was found that intravenous and subcutaneous injections of all of these were active in producing a greater or less increase in peristalsis. Sodium sulphate acted in this respect very much as sodium citrate did. The latter, however, tended to produce muscular twitchings in the voluntary muscles, a phenomenon which will be spoken of later. Sodium sulphate on the other hand could be introduced into the blood in relatively large quantities without producing any evil effects. The action of sodium sulphate on the intestine was found to be somewhat less than that of sodium citrate; but almost constantly 2-3 c.c. m/6 Na_{2}SO_{4} injected into the marginal vein of the ear caused a marked increase in the peristaltic movements of the intestine. I cannot at all agree with Hay and earlier writers who affirm that sodium sulphate injected intravenously produces no purgative effect. In all my experiments I have found it to have a very definite effect when introduced in this manner, and I can only attribute their results to the concentrated solutions used, or to other unfavorable conditions. The injection of solutions of sodium fluoride produces very active movements, although only small quantities can be administered on account of its poisonous nature.