IMMUNITY. 345 



represented by Behring in the light of an en- 

 tirely ontological specificity of the micro-para- 

 sites. The serum therapy must be placed, 

 therefore, in the same category with Pasteur's 

 inoculations for rabies, and not in that with 

 Koch's inoculations with tuberculin. Accord- 

 ing to this view one " species " of animal, man 

 for example, is naturally immune against a 

 " species " of micro-parasite ; immunity against 

 the " specific " disease of small-pox can be 

 gained only through " specific v small-pox 

 virus, " specific " tolerance of the toxin of 

 diphtheria, only through the " specific " diph- 

 theria toxin ; hence a complete^ immune 

 body must contain " specific " antidotes against 

 all these disease germs and also against their 

 poisons. 



The logical consequence of this doctrine as 

 Pasteur, Koch and Behring have shown, is 

 that against every " specific " infectious dis- 

 ease, a " specific " protective inoculation or an 

 attempt to establish a u specific " poison toler- 

 ance must be adopted as the method of preven- 

 tion or cure. The methods which have been 

 employed for this purpose have been differently 

 conceived and carried out in different epochs. 

 In 1638, a method of this sort was followed by 

 Robert Fludd, who prepared a remedy against 

 consumption from the sputum of consump- 



