CHAPTER V. 



DESTRUCTION OF BACTERIA BY CHEMICALS 

 AND THEIR PRACTICAL USE. 



IT has been shown how bacteria can be killed by heat, 

 and now the chemical methods of destroying infective 

 material will be discussed, and how this may be done 

 practically. Chemicals either in solution or as gas 

 are supposed to kill bacteria by one of several methods. 

 The whole bacterial body may be destroyed or the 

 protoplasm may be entered by a diffusion of the 

 substance through the cell wall with consequent 

 coagulation or solution. It is said also that the rapid 

 withdrawal of water absorbed by some salts may be 

 fatal to the microorganism. 



There is some confusion as to the terms used for 

 chemical bacteria-killing, and for this reason it may 

 be well to start out with Park's classification. (1) 

 Attenuation is when the pathogenic or vital functions 

 of the bacteria are temporarily diminished. (2) Anti- 

 septic action is when the bacteria are not able to mul- 

 tiply but are not destroyed; they will reproduce when 

 suitable conditions for life are restored. (3) Incom- 

 plete sterilization or disinfection is when the vegetative 

 forms but not the spores are destroyed. (4) Steriliza- 

 tion or disinfection is when both vegetative and spore 

 forms are destroyed ; this implies also the destruction of 

 any products of bacteria capable of producing disease. 



