Abstract

1. Lack of calcium and excess of potassium depress the response of the frog's ventricle very rapidly and the response is reduced to one half its original normal force in two or three seconds. Recovery of the ventricle occurs even more rapidly when it is irrigated with normal Ringer's fluid. Acid Ringer (pH 6.0) and sodium cyanide (0.001 molar) act far more slowly for they require about five minutes to reduce the response of the ventricle to one-half its normal force.

2. Changes in the frequency of stimulation do not affect the speed with which calcium lack depresses the ventricular response, and therefore it is concluded that calcium lack depresses the contractility of the heart but does not depress the recovery process.

3. The speed with which potassium excess depresses the response of the ventricle, and the extent of this action both depend on the frequency of stimulation. The action is more rapid and more powerful with a high than with a low frequency. It is therefore suggested that potassium excess interferes with the recovery process of the heart.

4. The rapidity with which calcium lack and potassium excess affect the ventricle suggests that they probably act on the cell surfaces rather than on the interior of the cells.

5. The fact that acid and cyanide act about 100 times more slowly on the ventricle than do changes in calcium and potassium concentrations suggest that the former pair act in some entirely different manner from the latter pair.

6. The speed at which acidity and sodium cyanide depress the response of the ventricle depends on the frequency of stimulation. The rate of action is about five times more rapid with a frequency of 50 per minute than it is with a frequency of 10 per minute.

These results are consistent with the view that acid and cyanide interfere with the recovery process of the cells and hence the ventricle is slowly poisoned with the products of abnormal metabolism.