RHYTHMIC RESPONSE IN PLANT AND ANIMAL 353 



yet on application of the acid there is seen to be a slight 

 revival of pulsation and a final arrest towards diastole. 



Identical nature of rhythmic phenomena in animal 

 and vegetable tissues. —We have thus found the responsive 

 phenomena of cardiac muscle to be in every respect similar 

 to those observed in the rhythmic tissues of Desmodium and 



FlG. 155. Arrest of Pulsation of Desmodium at ' Systole ' by Application 

 of Dilute Alkali at T 



Acid was next applied at 1, and the record shows its antagonistic action. 



Biophytum, the response of the latter being regarded as 

 practically that of Desmodium in a state of standstill. We 

 have seen that in these rhythmic animal and vegetable 

 tissues the fundamental characteristics are identical : 



(1) In all of them stimulus gives either maximum response 

 or none. 



(2) They all exhibit a long refractory period, during 

 which additional stimulus produces apparently no effect. 



(3) They are all incapable of being tetanised. 



And further, as regards the influence of various external 

 agencies on the two classes of rhythmic tissues, animal and 

 vegetable, the effects are also remarkably similar. Internal 



A A 



