(_D_) _By introducing a rubber balloon, to which is attached a graduated rubber tube, through a gastric fistula into the small intestine, and measuring rate of descent and force carrying it onward to anus._ _Technique of the experiment._—Dogs are suited for this. Hess in his experiments used the animal immediately after making the fistula; Brandl and Tappeiner waited for the fistula to heal, and used the same dog a number of times, usually waiting two weeks before using him again, so that he would completely recover from the previous experiment. The balloon is introduced into small intestine and then moderately distended with water through the tube. After it has passed some distance below the pylorus, the cathartic is injected through the tube, the instrument being so constructed that the medicine passes into the intestine just above the balloon; ferrocyanide of potassium is added to the solution so as to tell by its reaction with chloride of iron whether the cathartic solution is in the feces. This method causes no shock and is superior to opening the abdomen to determine peristalsis. By this method can be learned: (1) _The location of the peristalsis._ This is done by examining the graduated tube and noticing how many feet been drawn in. If after the cathartic has been introduced above the balloon it does not increase the rate of descent till it reaches the colon, it shows that the drug acts on the colon instead of the small intestine; aloes is an example of this. If it increases its descent in the small intestine, it shows that the drug acts on the small intestine. If the drug greatly increases its speed in both small and large intestines, then the drug stimulates peristalsis through the whole length. (2) _The rate of the peristalsis._ This is learned simply by noticing how fast the graduated tube is drawn in. (3) _The time of peristalsis._ When the tube is not being drawn in there is no peristalsis, at least where the balloon is; when the drug acts on the small intestine the peristalsis occurs early; and when on the large intestine, late. (4) _The force of the peristalsis._ This can be measured by pulley and bag of shot attached to the graduated tube. Of course it is necessary to learn first the lifting power of the peristalsis in the same dog without a cathartic. (5) _By injecting a solution of the cathartic into a ligatured loop of intestine in the living animal._ It is better to use a rabbit or dog that has been starved for several days so that the intestine will be empty. After several hours remove the loop and measure the amount of liquid. If it is increased the drug stimulates secretion. It must not be forgotten that the irritation of the ligature stimulates secretion, so it is better to have a similar loop for comparison.