Abstract: 1. The sensitivity of different segments of the intestine to the stimulation of tartar emetic was markedly different. When the drug solution was introduced into the isolated fistula of duodenum or jejunum, both vomiting and diarrhea may be observed. When the same solution introduced into the lower portion of ileum or colon of the same or other animals, the vomiting did not occur but the bowel movement alone (Shown in table 1).The aforementioned experiments also indicate that the gastrointestinal reaction was due to reflex. 2. The estimation of the amount of absorption of tartar emetic in the different segments of the intestine (duodenum, jejunum, ileum and colon): (1) The amount of absorption of tartar emetic was measured and compared with the concentration of tartar emetic in plasma after directly introducing the tartar emetic solution into the different fistulas in concious dogs. (2) Further studies have been made by directly measuring and comparing the amount of disappearance of drug from the intestional loops in anesthetized rabbits. The results indicate that the amount of absorption of tartar emetic from the upper segment of intestine such as duodenum and jejunum was greater than that in the lower segment as colon. 3. The degree of absorption of tartar emetic in the different pH media has been studied by continuous perfusion of the whole length of the small intestine with drug solution in the anesthetized rats. The results indicate that pH of the intestinal medium was an importion factor in the absorption of tartar emetic by intestine. In the acidic medium (pH 5.7) the amount of absorption of tartar emetic was markedly greater than in the pH 7.2 (Shown in table 4).