324 Chapter X 



[340] von Dungern 1 in my laboratory. This observer convinced himself 

 that "anthrax bacilli are weakened neither by the encapsuled bacilli 

 nor by the substances which they contain." These micro-organisms 

 do not interfere in the slightest with the anthrax bacilli either outside 

 or within the animal, and " when the anthrax infection does not be- 

 come generalised it is due to the fact that the anthrax bacilli are 

 ingested by the phagocytes at the seat of inoculation and destroyed 

 within these cells" (p. 183). 



In this action of foreign micro-organisms upon micro-organisms 

 against which we wish to protect the animal we have to deal with 

 something analogous to the condition we obtain when immunising 

 with normal serums or with any other kind of fluid. In both cases 

 immunity is rapidly established, but it is very transient and is con- 

 fined to a stimulation of the phagocytic resistance. Direct action 

 may also intervene, as in the case of Bacillus pyocyaneus, but it is 

 not indispensable. The animal whose phagocytes are in a condition 

 of superactivity can do without this direct action, its own resources 

 being sufficient to arrest anthrax. 



Following the same lines of investigation as those on the an- 

 tagonism between the anthrax bacillus and several other micro- 

 organisms, Klein 2 has demonstrated that, in order to prevent a 

 guinea-pig from contracting experimental cholera peritonitis, it is 

 only necessary to inject into it, the day before infection, a culture of 

 Tinkler and Prior's vibrio or of certain other bacteria. These ex- 

 periments by Klein served as the point of departure for Issaeff's work 

 which led to the discovery of the stimulating influence of all kinds of 

 fluids injected into the peritoneal cavity of guinea-pigs. 



In this transient immunity obtained with products foreign to the 

 micro-organism against which one is vaccinating, the most constant 

 and consequently most important part is again played by the phago- 

 cytes. But there is associated with it an influence, greater or less in 

 degree, of substances present in the serums, such as the microcytases 

 and fixatives, which are able to exercise a direct action on the patho- 

 genic micro-organisms. In all cases known and analysed up to the 

 present, the intervention of the living organism of the animal is 

 indispensable, consequently this form of acquired immunity against 

 micro-organisms cannot be regarded as being really passive. 



1 Ztschr.f. Hyg^ Leipzig, 1894, Bd. xvni, S. 177. 



2 Centralblf. Bakteriol. u. Parasitenk., Jena, 1893, Bd. xm, S. 426. 



