THEORIES OF IMMUNITY. 



belief of all but a few of the specialists in that 

 branch of medicine. 



His effort was to develop) the idea that cel- 

 lular digestion in unicellular organisms had 

 been transmitted by heredity to the superior 

 animals, and is preserved in the mesodermic 

 ameboid cells. These cells being able to en- 

 globe and digest all sorts of histological ele- 

 ments may well be able to apply the same 

 power to the digestion of the bacteria — and 

 that they are able to do this he demonstrated 

 in many cases by introducing bacteria into 

 lower animals and watching their englobing 

 and destruction by the ameboid elements. It 

 was evident that the simple demonstration of 

 this occurrence was not sufficient for the devel- 

 opment of the general theory, and he went on 

 to find diseases in the lower animals that were 

 illustrative of the same thing. This he suc- 

 ceeded in doing in the case of the daphnia, — 

 small Crustacea common in fresh water, — and in 

 them followed out and watched an actual 

 struggle between their leucocytes and the sj)ores 

 of a blastomycete ; on the one hand it often 

 happened that the cells were successful in 



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