Abstract

1. Digitalis strongly and directly stimulates the cardio-inhibitory center of the medulla.

2. Paralysis of the center by excessive action is shown by the escape of the heart during perfusion and by the failure of subsequent perfusions to produce inhibition.

3. Cumulative and persistent action on the inhibitory nerve center is indicated by the recurrence of various degrees of inhibition during subsequent perfusion with Ringer's solution.

4. Not only is the rhythm inhibited but there is a blocking of the passage of the contraction wave from the veins and sinus to the ventricle by a decrease in conductivity.