Abstract: The destruction of Divasid in the body and its binding with serum protein have been studied, using guinea pigs in the former and isolated frog hearts in the latter case. Divasid is a designation proposed for a cardiac glycoside preparation of Huang(黄维垣)from the seeds of Yang-Chiao-Ou(Strophanthus divaricatus(Lour.)Hook.et Arn.)As the potency of different batches of the preparation varies,so material of one and the same hatch (No.369)is employed throughout the experiments.The results are as follows: 1.Determined by the method of Hatcher and Brody(in the modification of Soviet Pharmacopoeia,1952)and the method of Knaffl-Lenz(in the modification of the Chinese Pharmacopoeia,1953),the cat unit of the present batch was found to be 0.333 mg/kg±0.0163(S.E.),3003 cat units being equivalent to one gram; while the guinea pig unit(g.p.u.)was 2.564 mg/kg±0.155,385 g.p.u,being equivalent to one gram. 2. When instead of the jugular vein the ileo-cecal vein was utilized for the infusion,the g.p.u,was found to be 6.535 mg/kg±0.1981,which is 2.6 times higher than the ordinary g.p.u.,apparently due to the destruction taken place in the liver. 3. When injected intravenously,the minimal lethal dose for g.p.was 2.3067 mg/kg(0.9 g.p.u.); orally,30.768 mg/kg(12 g.p.u.).The latter dose is 13.3 times higher. The destruction in the gastro-intestinal tract is the main cause,the liver can play only a minor ro1c. 4. Experiments with the Straub's frog heart preparation have shown that Divasid like K-strophanthin,is not bound with bovine serum. The author wishes to express his gratitude to Prof. Lu Fu-hua for his guidance in the performance of the work.