CELLULAR THEORY OF IMMUNITY 321 



of the chicken which, when chilled, contracted anthrax. 

 A microbe may be harmless for the species which carries 

 it, and may not be so for others, the resistance of which 

 is not organized in the same fashion. It will be under- 

 stood that it may be fatal to the young animal, whose 

 phagocytes are not inured, that it may develop where 

 the phagocytes are not numerous, and not where it 

 finds them in great numbers and better trained, etc. 

 And all this happens through the intermediary of cel- 

 lular secretions, that is to say through physico-chemical 

 agencies. It is evident that Claude Bernard and the 

 physiologists who feared to see Pasteur re-introduce into 

 science the idea of life as a hidden cause had in him 

 not an enemy of their doctrines, but a powerful ally. 

 We see also that the physicians were right in treating 

 him as a chemist. They were wrong only in pronouncing 

 this name with a disdainful air. With Pasteur chemistry 

 took possession of medicine and we can foresee that it 

 will not relinquish its hold. 



