Abstract
From the results here reported it appears that perfusion of a donor frog heart with Ringer''s sol. containing a Ca excess, unbalanced by K, results in the liberation of a substance having a positive inotropic effect on a 2nd frog heart. The action of this substance is additive with that of the accelerator substance liberated by stim. of the vago-sympathetic. The material is oxidizable, is destroyed by ashing or simple heating to near the boiling point for a few min., and it passes easily through a dialysis membrane. Its effect on a recipient heart is abolished by ergotoxine. These properties are similar to those described by Loewi for the accelerator substance liberated by sympathetic stimulation. Ca evidently sets free sympathin from the frog''s heart.

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