402 Chapter XII 



artificial immunity against toxins, has indicated to us that this is a 

 problem far more difficult of solution than is that of acquired im- 

 munity against micro-organisms. The mere fact that these latter 

 can still be found some hours or even days after their entry into 

 the refractory animal, affords a great advantage in these researches 

 as compared with those on toxins which are lost, often almost imme- 

 diately, after their injection. Consequently our knowledge of anti- 

 microbial immunity is more advanced than is that on immunity against 

 the soluble products of micro-organisms. 



The facts narrated in this chapter support the thesis I have 

 defended on the subject of immunity against micro-organisms — that 

 antimicrobial immunity in no way depends on a previous resistance 

 against the toxins. As a general rule the immunity against micro- 

 organisms is developed more readily than the immunity against 

 their toxic products and at an earlier stage. 



Although much still remains to be done in the elucidation of the 

 mechanism of antitoxic immunity, the principal data acquired on 

 the subject of this immunity have undoubtedly led to applications of 

 the highest importance, as will be set forth in one of the following 

 chapters. 



