BACTERIA IN DISEASE. 185 



diseases are the destruction of the bacteria by the cells of the 

 body (phagocytosis), the development of new substances 

 which neutralize their action (antitoxins) and the presence or 

 formation in the body of substances which destroy bacteria 

 (lysins). These phenomena are discussed in the chapter on 

 Immunity. A factor of less importance is the elimination of 

 bacteria by the excretory organs. Investigators who have 

 made experiments on animals disagree as to whether or not the 

 bacteria which have been injected into the body appear in the 

 urine before they have damaged the structure of the kidney. 

 The extent to which the excretory organs act in eliminating 

 bacterial toxins is not yet known. Some bacteria, as has 

 already been stated, may, in the end, produce substances that 

 are inimical to their own growth. 



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