CHEMICAL PHENOMENA IN LIFE 



may be called Chemical Stimuli. Their action is 

 quite comparable to the action on living matter 

 of physical stimuli, such as light, warmth, elec- 

 tricity and gravity. 



It is quite a general rule that substances which 

 produce poisonous effects on living cells when 

 applied in a certain concentration, influence living 

 cells quite differently when their concentration is 

 more diluted. Then stimulating effects are 

 regularly produced. Respiration and growth 

 reach a higher degree than without application 

 of the poison. For example, potato plants treated 

 with copper sulphate show darker green leaves 

 and more vigorous stems than normal plants. 

 We see that poisonous action does not depend 

 only on the chemical nature of substances, but also 

 on the concentration of the substance. We should 

 rather speak of poisonous effects than of poisonous 

 substances. The explanation of the phenomena 

 may be given by the principle of action and counter- 

 action. The poison for example, mercury chloride 

 or carbolic acid develops a retarding influence on 

 some processes in living protoplasm. Protoplasm 

 is by this action incited to react against the 

 injuring influence. This is done by an acceleration 

 of the chief processes of life respiration, growth, 

 and probably many others. So the toxic in- 

 fluence is paralysed. The successful counter-action 

 against the poisonous agent cannot, however, 

 take place when the toxic influence is too strong. 

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