384 BACTERIOLOGY. 



mined by the species of host-organism, and 

 the same property of the serum which has 

 been acquired or heightened by specific im- 

 munization or habituation to poison, not a 

 qualitative but merely a quantitative distinc- 

 tion. The stimulus that produces a state of 

 immunization and habituation to poison has 

 the visible effect of increasing the quantity of 

 active bodies in the blood serum. Only seem- 

 ingly in this case has a new qualitative char- 

 acter been added, for the bacterial components 

 found in the curative serum have nothing to 

 do with the antitoxic effect. The bacterial 

 substance constitutes merely the special form 

 of stimulus and may be altogether absent with- 

 out any change in the result if only in some 

 way or other there is provided* some sort of 

 stimulus which induces the specific cell terri- 

 tories and cells of the host to generate suf- 

 ficient quantities of the active bodies. 



The bacterial component, and this can be re- 

 garded as the sole specific element, is certainly 

 not essential to the formation of the antitoxin 

 as is seen from the following experiments, 

 which in great part we owe to Roux and his 

 pupils Calmette, Phisalix and Bertrand. 



i. The normal serum of healthy warm- 

 blooded animals acts in vitro upon specific tox- 

 ins just as if it contained specific antagonistic 



