TY - JOUR T1 - EXPERIMENTAL STUDIES ON HEART TONICS I. THE VARIABLE RESPONSE OF THE FROG HEART TO THE ACTION OF THE DRUG JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 635 LP - 655 VL - 36 IS - 4 AU - WILLIAM NYIRI AU - LOUIS DUBOIS Y1 - 1929/08/01 UR - http://jpet.aspetjournals.org/content/36/4/635.abstract N2 - The main factors influencing the variable response of the frog heart to the action of heart tonics are studied. 1. The individual variation using the U. S. P. one hour frog method may lie in: (a) differences in the absorption and (b) intrinsic factors of the heart. 2. The unlimited time-method in which the influence of absorption is eliminated shows nearly the same individual variation as the U. S. P. assay. 3. The intravenous application of the drugs which is entirely free from the influence of absorption gives similar varying results. The technic of the intravenous method is described. 4. In experiments on the isolated frog heart by the method of Straub where only intrinsic factors play a rĂ´le, the individual variation is still very marked. 5. The amount of alcohol as used in our work as solvent for the heart tonics is not responsible for the variation. The experiments prove that differences in the absorption of the heart tonics in the frog do not explain the high range of variation in the response of the heart to these drugs. The main reason for this variation lies in the frog's heart itself. ER -