GENERAL SURVEY 359 



Effect of Chemical Agents 



The effect of drugs on the rhythmic pulsation is modified 

 by the tonic condition of the plant, the strength of the 

 reagent, and the duration of application. 



Vapour of alcohol and dilute carbonic acid induce a 

 transient enhancement of amplitude with prolongation of 

 period. Stronger application induces an arrest of pulsation. 

 Dilute vapour of ether and carbon disulphide induce a 

 temporary arrest, revival taking place after quick substitu- 

 tion of fresh air. The action of chloroform is more intense 

 than that of ether. 



Copper-sulphate solution causes a permanent arrest of 

 pulsation. The poisonous reaction of potassium cyanide 

 is more powerful than that of copper sulphate. 



A very striking characteristic modification in the 

 rhythmic activity of animal tissue is found in the antagon- 

 istic action of acid and alkali on the pulsation. Application 

 of dilute acid induces in the heart an atonic reaction with 

 arrest of pulsation in the relaxed or diastolic condition. 

 The effect of alkali is the very reverse of this, the arrest 

 taking place in systole. These specific effects are repro- 

 duced in an astonishing manner in the rhythmic pulsation 

 of Desmodium. Dilute solution of lactic acid induces in 

 the pulsating leaflet an arrest at diastolic relaxation. The 

 application of dilute sodium hydrate induces, on the other 

 hand, exactly the opposite effect of arrest at systole (p. 339) . 



At the beginning of this work we took up the question 

 of the possibility of detecting internal changes in a plant 

 by subjecting it to a questioning shock. It has been shown 

 how the plant can be made to record its answer to an 

 impinging testing stimulus, and how the effects of environ- 

 mental changes may be read in the script made by the 

 plant itself. 



It has been shown that the variations in the plant's, 

 physiological activity, under changing external conditions 



