EFFECT OF STIMULUS ON LEAFLET 317 



to be exceeded when the state of standstill had been allowed 

 to persist for nine or ten hours. In these, stimulus failed 

 completely to evoke any response. 



Summary 



The leaflet of Desmodium comes to a state of standstill 

 by depletion of its store of energy. 



The pulsation may be revived by the action of various 

 stimuli, such as that of light or of induction-shock. 



Desmodium leaflet in a state of standstill gives a single 

 response to a single stimulus of induction-shock of moderate 

 intensity. In a typical case the latent period is -4 second, 

 the apex time 45 seconds, and the period of relaxation 120 

 seconds. The response-curve exhibits a flattened top. 



The response of Desmodium, like that of the cardiac 

 tissue, is characterised by a long refractory period. 



The rhythmic activity of the leaflet of Desmodium comes 

 to an end when its store of energy is depleted. A leaflet 

 isolated from external sources of stimulation is thus gradually 

 brought to a state of standstill. 



In this condition, response occurs under fresh stimulation. 

 If the depletion of energy had not been excessive, then a 

 moderate stimulus gives rise to multiple responses. But 

 under greater depletion even a very strong stimulus induces 

 only a single response. 



