368 PHYSIOLOGY OF BACTERIA 



protoplasm is perhaps one of the later stages of the death 

 process, and not one of the causes. 



(h) SUMMARY OF FACTS 



Bacteria die from chemical poisons in the same general 

 order that is found with death by heat, or by drying. 



Bacteria, which, by chemical poisoning, have lost 

 the power to multiply, may regain it if an antidote is used. 

 This complicates the definition of death. 



The same disinfectant does not act equally strong 

 upon all organisms. Certain genera and species are 

 more resistant to a certain poison than others. Well 

 known examples of special resistance are that of tubercle 

 bacteria against alkali, of aciduric bacteria against acid, 

 of many molds against formaldehyde. 



The toxicity of a disinfecting solution increases with 

 its concentration, but not always in direct proportion. 

 Different disinfectants behave quite differently, and 

 two different disinfecting solutions of equal toxicity 

 may vary widely if they are both diluted with the same 

 amount of water. 



The disinfecting power of a solution is increased by an 

 increase of temperature. 



SUMMARY OF THEORIES 



The fundamental reaction that causes death when a 

 chemical poison acts upon a living cell is still unknown, 

 despite several promising attempts to determine it. 

 Several theories exist; we may assume a chemical com- 

 bination of the poison with essential molecules, or 

 changes of interface tension which bring about a col- 

 loidal state of protoplasm, or a catalysis of some normal 

 catabolic cell process by the poison. 



