CHAPTER XIV. 



NATURE OF DISEASE {Continued). 



Actions of poisons in small doses Results of killing a 



few cells Malformation Enzymes Secretions and 



excretio7is -Acids, poisons, etc. Chemotactic plieiio- 



mena Parasitism Epiphytes and endophytes 



Symbiosis Galls. 



Physiological research has shown that the 

 respiratory activity of cells may be increased by 

 small doses of poisons, and even that growth may 

 be accelerated by them e.g. chloroform, ether 

 and, still more remarkable, that fermentative 

 activity may be enhanced by minute doses of such 

 powerful mineral poisons as mercuric chloride, 

 iodine salts, etc., and that the cells may be 

 gradually accustomed to larger doses without 

 injury. Unfertilised eggs of insects have been 

 started into growth by treatment with acids and 

 those of frogs with mercury salts, and the ger- 

 mination of beans quickened by various poisonous 

 alkaloids. In other words, graduated doses of 



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