The idea that under certain conditions the two ventricles do not beat absolutely synchronously is an old one, and was used by C. J. B. Williams and by Skoda1 to explain the production of split heart sounds. Experimental evidence of this asynchronism was given in 1890 by Philipp Knoll,2 who showed that the right ventricle contracted before the left during vagus stimulation. Knoll's experiments were confirmed by Léon Fredericq3 (1906) and his pupil Stassen4 (1907). The latter showed that if ventricular extrasystoles were produced while the vagi were being stimulated, the ventricle in which the extrasystole was produced contracted 0.02 to 0.03 second before the other ventricle.
The idea that under certain conditions the action of the two ventricles might be so completely dissociated that a contraction of the one might be said to occur without the contraction of the other, was pro