THEORIES OF IMMUNITY. 



fectious serum — when the transformation of the 

 cholera spirilla into granules promptly made its 

 appearance. 



This result was what led Bordet (Ann. de 

 Flnst. Pasteur, 1895, T. IX, p. 462, and 1896, 

 T. X., p. 760) to study the intimate nature of 

 the reaction. He was successful in producing 

 it, not only by adding a little of the peritoneal 

 fluid to the specific serum, but also by adding a 

 little of the fresh blood from the same animal 

 (from which the peritoneal fluid had come). 

 These and other results of his work brought him 

 (Bordet) to the generalization that the destruc- 

 tion of the bacteria in immunized animals re- 

 sults from the action of two substances, — one of 

 these is the alexine of Buchner, which under 

 normal conditions is to be found in the leu- 

 cocytes. It produces bacteriolysis properly so- 

 called when it exists normally within the cells, 

 and also when it has escaped from them as 

 the result of phagolysis. There must, however, 

 be present a second substance in addition to the 

 alexine, and this is the " substance sensibilisa- 

 trice " of Bordet, which circulates in the plasma 



32 



