IMMUNITY. 335 



gory with the phenomena which have been 

 associated with the name of Mithridates, the 

 king of Pontus, who fortified himself against 

 poison by taking antidotes. The peculiar, 

 specific influence of the body-cells may in itself 

 suffice for our complete understanding of the 

 matter. A specific influence of this kind, how- 

 ever, as may be inferred from our previous ex- 

 position, is dependent upon specific external 

 conditions only in so far as the surroundings 

 stimulate or set free predispositions already 

 existing, as when for instance they cause a 

 specially marked activity of the body cells 

 which differs from the former condition only 

 in a quantitative direction. Since the body- 

 cells are not directly available for experiment, 

 and we are often able to gain information as to 

 their content of energy only indirectly through 

 the setting free of energy, many investigators 

 draw the fallacious conclusion that the speci- 

 ficity of the exciting germ is the sole determin- 

 ing factor and that a new quality is involved 

 in the change that takes place in the organism. 

 The fact is important also that the active 

 anti-toxins generally confer no immunity. If 

 cultures of tetanus or diphtheria bacteria or of 

 some other parasite be heated to about 65-7o 

 their specific toxic activity is taken away, while 

 their capacity for conferring immunity upon 



