THE ACTION OF STROPHANTHIN ON THE LIVING CAT'S HEART.

1. Cats vary considerably in their susceptibility to strophanthin and in the extent of the difference between the minimum lethal dose and the minimum toxic dose. 2. The amount of strophanthin necessary to produce a toxic effect in a given cat is independent of the speed of administration to a period of 4 hours. An improvement in the clinical administration of the drug is thereby indicated. 3. A theory of the action of strophanthin is formulated which reconciles the results which point to the importance of the total amount taken up by the heart with those inidicate that the concentration of the drug is the determining factor.