574 CIRCULATION OF BLOOD AND LYMPH. 



is maximal for that condition, that is, does not vary with the 

 strength of the stimulus. As was said above, this property is not 



Fig. 236. To show the effect of a short electrical stimulus applied at different times 

 in the heart beat. (Marey.) The record is taken from the frog's heart. In 1, 2, and 3 the 

 stimulus (e) falls into the heart during systole (refractory period) and has no effect. In 

 ' j' ' r' ,1 8 J the stimulu f alls into the heart toward the end of systole or during diastole, 

 a s * llo ed y an extra systole and corresponding compensatory pause. It will be 



systole and corresponding compensatory pai 



at tne latent neriod ( ' 



shorter t 



D i?5?f* _ that the latent Period (shaded area) between the stimulus and the extra systole is 

 ' '"he longer the diastole has preceded before the stimulus is applied. 



