IMMUNITY. 375 



rectly dependent upon the condition of the 

 whole body. The tissue juices also are able to 

 interpose in the contest, by virtue of the active 

 proteid substances they contain. That very 

 quality, however, which, according to Behring, 

 is the cardinal one, namely, the possession of 

 anti-substances, the very character wherein the 

 " specificity " of the parasite is most sharply 

 expressed, appears to be of secondary signifi- 

 cance. The anti-substances are frequently 

 absent where immunity exists, and their pres- 

 ence or absence is without regularity. This 

 fact helps to perplex us still more about the 

 phenomenon of " specificity," so far as " spe- 

 cificity " is looked upon as an explanation of 

 the real heart of the matter, or the " specific" 

 microparasite is regarded as the exclusive factor 

 in the production of immunity. Where Behr- 

 ing and Pf eiffer speak of the specificity of para- 

 sites and anti-substances it is more correct to 

 speak simply of the activity of body cells and 

 fluids. 



If stimuli act upon a normal physiological 

 condition that exists as a momentary adapta- 

 tion or upon a condition of health regained 

 after a complete cure, the stimuli that some- 

 times effect protection and cure may, by repe- 

 tition, bring about at times a more ready 

 discharge of energy (as we witness in the 



