THEORIES OF IMMUNITY. 



determined, that an inflammatory exudate must 

 be considered as a reaction against all sorts of 

 lesions, and that exudation is a primitive phe- 

 nomenon, older than the nervous system or the 

 blood-vessels. 



At the time these researches were going on 

 (1882), the general theory in regard to inflam- 

 mation was that it was, at least in most part if 

 not wholly, the result of bacterial action. As a 

 result of this belief, the conclusion was reached 

 that diapedesis and the gathering of the white 

 corpuscles in inflammatory disease was to be 

 looked upon as a means of defence of the tissues 

 against the bacteria, and that the leucocytes 

 served to englobe and destroy them. Upon 

 such a hypothesis, the explanation of inflamma- 

 tion becomes at once most clear and simple, and 

 it was such an explanation that Metchnikoff set 

 himself to prove, if possible. 



The general belief of the pathologists at 

 that time was that the bacteria found a 

 favorable location in the leucocytes and were 

 carried about by them instead of being de- 

 stroyed. So that to secure recognition for his 

 theories he was obliged to overcome the then 



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