230 Chapter VIII 



[242] of recurrent fever in the organism of guinea-pigs prepared by pre- 

 vious injections is governed by laws the same as those established 

 for acquired immunity against vibrios. The spirilla are ingested and 

 destroyed by the phagocytes, except where phagolysis occurs, in 

 which case the cytase, being set free, attacks the micro-organisms 

 outside the leucocytes. 



After his discovery of the granular transformation of vibrios, 

 R Pfeiffer, in collaboration with several of his pupils, set himself to 

 discover how far this phenomenon was general in acquired immunity. 

 He directed his attention to the typhoid cocco-bacillus, upon which 

 he had already published^ a very detailed account of work carried 

 out in conjunction with Kolle. These observers availed themselves 

 of the discovery made by Beumer and Peiper^, and Chantemesse and 

 WidaP and confirmed by other observers, that laboratory animals, 

 especially mice and guinea-pigs, could be easily vaccinated against 

 the fatal disease set up by the micro-organism of typhoid fever. As 

 in the experimental infection of the guinea-pig by the cholera vibrio, 

 the vaccination of the animals against the typhoid bacillus could be 

 carried out very easily, either by using sterilised cultures or the fluids 

 of cultures deprived of their organisms by filtration. In the small 

 laboratory animals a most marked acquired immunity may tlius be 

 obtained, and the study of the phenomena which appear in the 

 vaccinated organism aflbrded evidence of a general analogy witli those 

 which have been observed when vibrios are used. In the peritoneal 

 cavity of the immunised guinea-pigs, Pfeiffer's phenomenon proper 

 does not appear, that is to say, only a few of the bacilli are trans- 

 formed into granules, the large majority retaining their bacillary 

 form ; still they are evidently greatly damaged : they become motion- 

 less and agglutinate more or less completely into clumps. If, however, 

 a few of these micro-organisms are sown on nutritive media, they 

 multiply freely and give abundant growths. The peritoneal fluid, 

 then, acts most unmistakably upon the typhoid bacillus, but in 

 a much less degree than does the peritoneal exudation of guinea- 

 pigs upon the cholera vibrio when immunised against that organism. 



[243] In both cases we have a pronounced phagolysis which sets free the 

 microcytase, whose action on the vibrio is more marked than on 

 the bacillus of typhoid fever. This extracellular action on the 



1 Ztschr.f. Hyg., Leipzig, 1896, Bd. xxi, S. 203. 



2 Ibid. 1887, Bd. ii, S. 110. 



' Ann. de VInst. Pasteur, Paris, 1892, t. vi, p. 755. 



