Certain similarities in the action of the glucosides of the digitalis group and of calcium on the heart have led to the hypothesis that they may be related in their action.1 There is no general agreement as to the character of this relation. Some investigators have maintained that their effects are partially or completely additive;2 others, that they are truly synergistic;3 in other words, the effects resulting when they are given together exceed the effects to be expected from the sum of their individual actions. The term potentiation is at times used in a sense equivalent to that of synergism.
The experiments presented here are concerned with the effects on the previously digitalized animal of calcium salts injected intravenously. This particular problem has evident special importance in clinical medicine.
PROCEDURE AND RESULTS
Effects of Calcium Alone.
—The effects on the heart of calcium salts injected intravenously into