INFECTION AND IMMUNITY. 461 



reasonable solution, and even now there remain a num- 

 ber of important points that are more or less veiled in 

 obscurity. 



Conspicuous among the observers who have endeav- 

 ored to explain the modus operandi of immunity may 

 be mentioned Chauveau, Pasteur, Metclmikoff, Buch- 

 ner, Flugge and his pupils (Smirnow, iSirotinin, Bitter, 

 Nuttall), Fodor, Hankin, and Pfeiffer. In the follow- 

 ing pages we will present briefly the result of investi- 

 gations by these various authors. 



In 1880 Chauveau'^ suggested an explanation for the 

 phenomenon of immunity that has since been known as 

 the "retention hypothesis." It is, in short, as follows : 

 that the immunity commonly seen to exist in animals 

 that have passed through an attack of infection from 

 a subsequent outbreak of the same malady, and likewise 

 the immunity that has been produced artificially by 

 vaccination, exist by virtue of some bacterial product 

 that has been retained or deposited in the tissues of those 

 animals, and that this product by its presence prevents 

 the development of the same organisms if they should 

 subsequently gain access to the body. 



Bearing upon this view the experiments of Sirotinin,^ 

 made with cultures of various pathogenic bacteria, 

 demonstrated that, in so far as culture-experiments were 

 concerned, the only substance produced by growing 

 bacteria that could be in any way inimical to their further 

 development were substances that gave rise to altera- 

 tions in the reaction of the medium in which they were 

 developing — i.e., acids or alkalies produced by the bac- 

 teria themselves. So long as the organisms were not 



Comptes-reDdus, etc., July, 1880, No. 91. 

 - Zeitseh. fur Hygiene, 1388, Bd. iv. 



