324 BACTERIOLOGY. 



highly virulent bacillus. These organisms are injected at 

 intervals of from eight to twelve days. By means of this 

 treatment a serum is obtained which is of limited cura- 

 tive value, but of very marked protective value. Poly- 

 valent serums do not seem to give any better results. 

 Kolle questions whether it will ever be possible to pre- 

 pare antitoxic pest-serum, because so far we are unable 

 to demonstrate a true pest-toxin. 



The unsatisfactory results with serum therapy in 

 plague in a number of epidemics cannot be attributed, 

 according to the investigations of Hetsch and Ilimpau, 

 to the absence of specific amboceptors in the pest-serum 

 for bacillus pestis. Even in the earlier investigations 

 on the estimation of the value of the pest-serum, Kolle 

 was lead to doubt whether the serum conformed exactly 

 with the laws of bactericidal serums ; in other words, 

 whether the pest-serum acted as a purely bactericidal 

 serum or not. It is true that some bacteriolytic action 

 can be demonstrated in the pest-serum ; but Markl was 

 able to show that with virulent cultures the leucocytes 

 play a most important part in the destruction of the 

 bacteria when injected into the peritoneal cavity of an 

 animal. Kolle concludes, therefore, that the pest-serum 

 is neither a purely antitoxic serum, like that of diph- 

 theria and tetanus, nor a purely bactericidal serum, like 

 that of cholera and typhoid, but that its action rests 

 probably much more upon substances the biological 

 character of which is as yet undetermined, in addition 

 to some bactericidal action. In this respect it corre- 

 sponds somewhat with the anthrax serum, as shown by 

 the experiments of Sobernheim. For this reason Kolle 

 calls the pest-serum an " anti-infectious " serum, as he 

 believes that by this designation its biological action is 



