A-C shocks of varying parameters affecting the heart

It is well known that both the human and the dog's heart may be thrown into ventricular fibrillation by 60-cycle a-c shocks, resulting in the cessation of circulation followed by death. There are, however, little data available as to the magnitude of the current of various durations that will result in fibrillation, nor is there much information as to how the induction of fibrillation is influenced by the timing of the shock in the heart cycle. Ferris, Williams, Spence, and King1 found that the sheep's heart was most vulnerable to shocks that fell during the T phase of the electrocardiogram of the heart.