CHAPTER IX 



DISINFECTION 



THE object of modern bacteriology is not merely to ac- 

 cumulate tested facts of knowledge, nor only to learn 

 the truth respecting the biology and life-history of bacteria. 

 These are most important things from a scientific point of 

 view. But they are also a means to an end ; that end is the 

 prevention of preventable diseases and the treatment of any 

 departure from health. In a science not a quarter of a 

 century old much has already been accomplished in this 

 direction. The knowledge acquired of, and the secrets 

 learned from, these tiny vegetable cells which have such 

 potentiality for good or evil have been, in some degree, 

 turned against them. When we know what favours their 

 growth and vitality and virulence, we know something of 

 the physical conditions which are inimical to their life; 

 when we know how to grow them, we also know how to 

 kill them. 



We have previously made a cursory examination of the 

 methods which are adopted for opposing bacteria and their 

 products in the tissues and body fluids. We must now 

 turn to consider shortly the modes which may be adopted 

 in preventive medicine for opposing bacteria outside the 

 body. 



It will be clear at once that we may have varying 

 degrees of opposition to bacteria. Some substances kill 

 bacteria, and they are known as germicides ; other sub- 

 stances prevent their development and resulting septic 



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