﻿158 STRONG. 



the injection of 1 oese of a 24-hour slant agar culture of Bacillus pestis 

 suspended and killed in 1 cubic centimeter of 0.085 saline solution, I 

 decided to investigate whether any immune substances became developed 

 in the serum of the inoculated individuals. It did not seem possible 

 to me that any appreciable degree of immunity could be acquired from 

 these inoculations, owing to the small size of the dose and the very mild 

 local and general reaction which resulted from the injections. I therefore 

 studied the agglutinative and bactericidal reactions of the blood serum of 

 12 cases, 6 of whom had been inoculated two weeks and 6 three weeks 

 previously with 1 oese of the killed pest culture. The agglutinative 

 reactions were performed by the macroscopic method and the bactericidal 

 reactions according to the one suggested by Neisser and Wechsberg. No 

 traces of agglutinins or of bacteriolysins could be demonstrated in the 

 sera of any of the individuals. 2 Obviously, these experiments in them- 

 selves were not considered to be conclusive evidence of the fact that no im- 

 munity was conferred upon the inoculated, since it was already recognized 

 at this time that these antibodies were frequently and indeed, usually, 

 not encountered even in the blood sera of individuals who had recovered 

 from an attack of plague and were immune to this disease. 3 Therefore, 

 experiments in animals were resorted to in order that more information 

 on this subject might be obtained. Ten guinea pigs were inoculated 

 subcutaneously, each with the same dose that was being employed in 

 the general human inoculations in this city. After two weeks the im- 

 munity of these animals was tested in the following manner. One oese 

 of a virulent pest organism was suspended in 1 cubic centimeter of 0.085 

 saline solution and 5 oesen of this suspension rubbed over a freshly shaved 

 area on the abdomen of the guinea pig. All of the animals succumbed to 

 acute pest infection, demonstrating conclusively that an immunity of 

 appreciable degree had not been produced. A short time after, the 

 important paper of Kolle and Otto * was published in which the unfa- 

 vorable results from the immunization of guinea pigs with large doses 

 of killed agar cultures of the pest bacillus or with Haffkine's proplrvlactic 

 were reported. It therefore seemed to me, at that time, more advisable 

 to experiment further with other methods of immunization against 

 plague, before insisting upon the use of larger amounts of more virulent 



= These experiments were undertaken at this time because the statement had 

 previously been made that agglutinins, at least in some cases, had been demon- 

 strated in the blood serum of human beings who had been inoculated against 

 plague a short time before with Haffkine's prophylactic, a conclusion which I 

 have not been able in any manner to confirm. 



3 Experiments demonstrating the fact that animals immune to pest infection 

 may still show no traces of agglutinins in their blood, together with those 

 demonstrating the absence of a true bacteriolytic action of plague immune serum, 

 will be presented later in this paper. 



4 Ztschr. f. Hyg. u. Infect ionskrankh., Leipz. (1903), 45, 507. 



