MECHANISM IN INFECTIONS WITH SEMIPARAS1TES 83 



Another point of difference also exists which is important, for 

 whereas in the anthrax experiment the primary bactericidal effect was 

 due to an associated leukocyte and serum action, possibly in the sense 

 of Schneider's leukins, the primary destruction of the cholera vibrios 

 was essentially brought about by the normal bacteriolysins of the 

 serum. Whether during the second phase of the cholera experiment, 

 when the leukocytes appear, a leukin action also takes place, has not 

 yet been established, but is, of course, possible. Then, again, while 

 animalization (encapsulation) of the anthrax bacilli leads to success- 

 ful resistance against phagocytosis, the corresponding changes which 

 take place in the cholera vibrio and the typhoid bacillus and which 

 are represented by an hypertrophy of the ectoderm, do not lead to 

 the same degree of protection. 



Evidently, then, there is a marked difference in the character of 

 the strife between the defensive forces of the guinea-pig and the two 

 types of organisms. On the one hand, the anthrax bacillus gains 

 the upper hand through its successful resistance to phagocytosis and 

 the inhibitory effect of its aggressins upon the production of leukins, 

 even though the appearance of the leukocytes at the point of infection 

 is not seriously impeded. In infections with the semiparasites, on 

 the other hand, the organisms conquer essentially through the 

 negatively chemotactic effect of their aggressins upon the cells, 

 which are thus kept at a distance and through the resistance of the 

 animalized individuals to the ordinary bacteriolytic influences of 

 the serum. 



Between the two extremes which have been represented above, 

 i. e., the effect following the injection of large and of subinfectious 

 doses of the cholera vibrio every possible gradation is possible and 

 can actually be reproduced in the animal experiment. If thus the 

 minimal infecting dose is injected there will usually be a primary 

 bacteriolysis of considerable extent, which then gives way to a gradu- 

 ally developing increase in the number of the organisms. At first, 

 as the leukocytes begin to appear, this proceeds slowly, but after a 

 little while the organisms definitely secure the upper hand and coin- 

 cidently the further influx of cells is more or less completely arrested 

 and the disease pursues its course to a fatal determination. 



That the leukocytic insufficiency is really the deciding factor in the 

 victory of the bacteria in such a case can be very well shown by 

 previously injecting the animal with the leukocytes of a second one 



