NORMAL HEART-STIMULATION OF VENTRICLE. 



579 



(2) That after the refractory period has elapsed stimulation 

 causes a reduplication of the beat (Fig. 165, c). 



FiQ. 165. 



Stimulation of Ventricle (minimal). 



a and i, stimulation in different phases of refractory period. 

 c, stimulation after refractory period has passed, showing different 

 forms of reduplication. 



(3) The latency of this reduplicated beat becomes distinctly 

 shorter as the systole passes into the diastole. Thus supposing 

 the value of a single cardiac systole to be l'-3, stimulation fall- 

 ing just at the maximum of a beat will cause a reduplicated 

 beat with a latency of 0-33. When the stimulation occurs half 

 way down the curve of relaxation, the latency is 018 or 02, and 

 when applied at the instant before the abscissae would have 

 been reached the latency is only 0'13. 



(4) Where acceleration or reduplication occurs, the sub- 

 sequent diastolic pause is prolonged, so that the time occupied 

 by the two beats, the interval between them longer or shorter, 

 and the subsequent pause, is nearly equal to the time which 

 would be occupied by two normal beats with their associated 

 diastolic pauses (Fig. 165, c). 



2 p 2 



