IV. 



SELF-LIMITATION AND IMMUNITY 

 IN DISEASE. 



GREAT questions are arising among us as the out- 

 growth of bacteriology, the most important ques- 

 tions, probably, with which modem medicine has to 

 deal; namely, those concerning self -limitation of and 

 immiinity from the infectious diseases. This is the di- 

 rection in which all eyes are turned, and this is the 

 direction in which we hope to see the triumphs of 

 medicine in the near future. This I say, of course, 

 with the understanding that the broad preventive 

 measures belonging to sanitary science are not under 

 present consideration. 



It was not long after the discovery of specific path- 

 ogenic bacteria that the question began to be raised: 

 How do these minute organisms produce their effects? 

 Nor was it long before it had been clearly shown that 

 the harm was not done by the mere presence of micro- 

 organisms in the body; in other words, that a mechan- 

 ical explanation was not sufficient save in a very lim- 

 ited and exceptional way. Almost equally untenable 

 was the theory that the bacteria,^ in their growth, 



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