CONDUCTION IN DEPRESSED CARDIAC MUSCLE AND ITS RELATION TO THE THEORY OF PARTIAL HEART BLOCK

Abstract

By means of a number of chambers and curtains, the conduction rate is depressed in a stretch of turtle heart muscle lying between 2 normal portions and the moment of arrival of the contraction is recorded at 5 points along the strip. When the middle portion is depressed by an excess of KCl the conduction rate falls off along a gradient. Since this gradient obtains irrespective of the direction in which the impulse is travelling, the conduction must be decremental. Weakening the impulse entering the region of decrement steepens the grade of the decrement. An hypothesis of partial heart block is developed based upon decremental conduction and upon the conduction theory which attributes impulse propagation to self-stimulation by the action potential.