In studying the purgative action of these salts, two criteria may be considered, namely, the actual passage of faeces, and secondly merely the increase of peristalsis and secretion not necessarily accompanied by defaecation. The former is of course the object of purgation, and unless a salt produces an actual passage of faeces it cannot strictly be termed a purgative. When this has been established, however, it is of much greater advantage to use the other criterion in studying the action of the solutions on the intestine. Any salt which in small doses produces an increased peristalsis will with a more prolonged action and perhaps larger doses produce actual purgation. Therefore in the first rough test as to the action of the salts I have used the actual passage of faeces as the criterion of the action. In this case no morphine is given the animal and its intestines are not exposed as in the other experiments where the movements are directly watched. In these tests the animals were kept in boxes, the bottom of each of which was covered by a large sheet of paper. During a certain time preceding the injection of any solution the animals were watched and the faeces collected and weighed. Half of the animals were kept as controls, and the rest subjected to injections of various solutions. The average weight of the normal faeces was compared with the weight of the faeces passed during the same time by the animals receiving the injections. The faeces were collected and weighed each hour during the first six hours following the first injection. The chief purgative effect usually took place during the first two hours. Although there was considerable individual variation in the rabbits, there was found to be a constant increase in the amount of faeces following the subcutaneous or intravenous injection of one of the salts. This amount varied from two to six times the average normal weight. Sometimes the increase was much greater and in many cases the nature of the faeces was much changed. The normal faeces of the rabbit consist of dry hard definitely formed masses. Following the purgative, they become soft and unformed, and may as in the case of NaF and BaCl_{2} be semifluid.