From these experiments, in which every precaution was taken, it seems certain that a definite increase in the secretion of fluid into the intestine follows the administration of barium chloride, and sodium citrate, the former of which is a saline purgative of a more powerful type, while the latter is among the milder purgative salts. It is of especial interest that these salts do not produce the increase of fluid on account of an irritating effect on the mucous membrane of the intestine. The action takes place, as shown in the experiments, when they are introduced subcutaneously or directly applied to the peritoneal surface of the intestine. Further, the solutions were practically isosmotic with the blood, and for this reason and from the fact that they were applied to the peritoneal surface of the intestine the osmotic pressure of the solution could play no part in causing fluid to enter the lumen of the gut. Also it is obvious that any possible effect which the purgatives may have in delaying absorption from the intestine (Wallace and Cushny) could have nothing to do with the production of this increased amount of fluid in the loops experimented with. The fluid produced is clear and either colorless or slightly yellow. It has an alkaline reaction and is apparently quite similar to the normal intestinal secretion. I have made no experiments to determine its powers of digesting and have no data concerning this point. There are no signs of its being of an inflammatory nature. Thinking that the manipulation of the intestine and the tying off of loops might influence the results, I estimated from the examination of a large number of rabbits of the same size (about 1,200 g. in weight) the quantity of fluid which is normally found in the small intestine. It was found that there was hardly ever more than 10 c.c., and usually only 5 or 6 c.c. of fluid in addition to a small amount of semifluid food material. To a rabbit in which the intestines seemed almost empty, a small dose of barium chloride was given locally by pouring an m/8 solution on the loops. The characteristic effect of the barium followed, and after one hour the small intestine was tied off by ligatures and removed. It was found to contain 22 c.c. of a clear yellowish fluid. In a second rabbit which received the same treatment 34 c.c. of a similar fluid were found in the small intestine. As will be shown in a later chapter, a secretion of fluid into the lumen of isolated loops of intestine removed from the body may be produced by immersing the loops, with their ends tied, in solutions of various saline purgatives. In m/8 solutions of NaCl, Na_{2}SO_{4}, and sodium citrate no secretion was obtained in these loops. In m/2 solution of these salts, however, a distinct measurable quantity was regularly produced; m/8 solutions of NaF brought about a secretion, and in all solutions containing BaCl_{2} a distinct secretion of fluid was obtained. This will be described in detail later on.