A Demonstration of Man of Electromotive Changes Accompanying the Heart's Beat

If a pair of electrodes (zinc covered by chamois leather and moistened with brine) are strapped to the front and back of the chest, and connected with a Lippmann’s capillary electrometer, the mercury in the latter will be seen to move slightly but sharply at each beat of the heart.1 If the movements of the column of mercury are photographed on a travelling plate simultaneously with those of an ordinary cardiographic lever a record is obtained as under (Fig. 1) in which the upper line h.h. indicates the heart’s movements and the lower line e.e. the level of the mercury in the capillary. Each beat of the heart is seen to be accompanied by an electrical variation. The first and chief point to determine is whether or no the electrical variation is physiological, and not due to a mechanical alteration of contact between the electrodes and the chest wall caused by the heart’s impulse. To ascertain this point accurate time-measurements are necessary; a physiological variation should precede the movement of the heart, while this could not be the case if the variation were due to altered contact. Figure 2 is an instance of such time-measurements taken at as high a speed of the travelling surface as may be used without rendering the initial points of the curves too indeterminate. It shows that the electrical phenomenon begins a little before the cardiographic lever begins to rise. The difference of time is however very small, only about .025′′, and this amount must further be diminished by .01′′ which represents the “lost time” of the cardiograph. The actual difference is thus no greater than .015′′, and the record is therefore, although favourable to the physiological interpretation, not conclusively satisfactory.