﻿1 84 STRONG. 



Kossel and Overbeck " also stated that rats could sometimes be immunized 

 with the filtrates of bouillon cultures which were killed by heating at from 56° 

 to 60° G.j although no details of the experiments are given. Markl 45 believed that 

 a soluble pest toxin as well as some metabolic product was formed in the filtrate 

 of young bouillon cultures and of those grown at a low temperature, with which 

 antitoxic immunity could be obtained and an antitoxic serum produced in 

 horses. The animals with which he experimented certainly acquired a tolerance 

 against the injection of the filtered cultures, but the immunity against pest 

 infection was not tested in any of them ; moreover, Kolle ia was unable to produce 

 a serum of any value with such cultures, although from repeated inoculations 

 of filtrates of bouillon cultures from eight to ten weeks old he was able to obtain 

 a serum of very low agglutinative and protective power. It would appear from 

 these experiments, that the plague bacillus does not readily undergo autolysis 

 and liberate free antigenetic receptors even in old bouillon cultures. 



Besredka " found that a separation of the pest endotoxin from the bacilli 

 occurred when dried pest bacilli, physiologic salt solution and normal serum 

 of the horse were mixed and allowed to stand over night at the temperature of 

 the ice box. 



Upon centrifuging this mixture and separating the bacteria, the clear fluid was 

 found to contain most of the pest toxin. The precipitated bacteria were found 

 to have lost their toxic action to a great extent, but not their immunizing power. 

 Nine mice were each inoculated with 0.002 milligram of these bacilli "atoxique." 

 Five of the animals survived the inoculation and the course of the infection was 

 prolonged in the remaining four. 



Owing to the success I had met with in immunizing both man and 

 animals with the free receptors obtained from the cholera spirillum 

 by autolysis, similar experiments were undertaken upon animals with 

 the plague bacillus. 



In the first experiments, 48-hour agar slant cultures of the virulent 

 strain were suspended in a small quantity of distilled water, heated 

 during one to two hours at 60° C, and after being placed for several 

 days in the incubator at 3?° C, were filtered through a Berkefeld candle. 



Immunization of monkeys with the free receptors of the plague 

 bacillus. — Experiments with such filtrates are recorded in Series 7 and 

 26 pp. 221 to 223. Xine monkeys were inoculated subeutaneously with 

 various amounts of the free receptors. Only two were found to be immune 

 and to survive the infection when their immunity was tested from ten to 

 fourteen days after the first inoculation. The results of these experi- 

 ments were so unfavorable that attempts to obtain the free receptors 

 in a somewhat different manner were instituted. 



The further experiments of this nature with the free receptors of 

 the organism of pest will be described in the next section of this paper 

 devoted to the subject of immunization with plague aggressin. since, 

 owing to the work of Bail and his associates, the term "aggressin" has 

 now become well established in medical literature. 



" Hyg. Rund. (1901), 11, 103. 



46 Ztschr. f. Hyg. u. Infectionskrankh., Leipz. (1901), 37, 401. 



48 Festschrift f. Robert Koch (1903), 352. 



"Ann. d. Vinst. Pasteur (1905), 19, 479. 



