Abstract
Summary
Study of the action of cardiac glycosides on strips of turtle ventricle indicates that the positive inotropic effect produced by those drugs does not result from primary stimulation of contractility but that it will occur only after there has been some suitable change in muscle metabolism. Beat depression caused by rapid stimulation, cold, calcium want, or excess potassium was not improved by digitoxin. Reduced contraction height due to increased acidity was partly offset by digitoxin. When contractility was depressed by various chemicals digitoxin usually increased the beat provided spontaneous recovery had been incomplete.
Ouabain produced effects comparable to digitoxin with approximately half the concentration. It did not act more promptly or cause relatively greater increases in beat.
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