Action of Monoiodoacetic Acid upon Muscular Function. : Part II. Action of Monoiodoacetic Acid upon Cardiac Muscle.

1. The inhibition of the heart beats through vagus nerve stimulation is more pronounced in the poisoned heart muscle than in the normal one. The degree of contraction recovers gradually after the cessation of stimulation, it shows no phase of compensation. 2. The absolute refractory period of the poisoned heart muscle diminishes as the poisoning proceeds.3. The shortening of the absolute refractory period of the poisoned heart muscle through the application of acetylcholin is maintained long after the removal of acetylcholin, though it recovers its previous condition in the normal heart muscle.4. The shortening of the absolute refractory period of the poisoned heart muscle through the vagus nerve stimulation does not recover after the cessation of the stimulation, and if the stimulation be continued longer, the refractory period becomes shorter. 5. In the last stage of poisoning the heart muscle falls spontaneously or by a single stimulation into a peculiar type of contracture.