Researctes on Certain Problems of Plague Immunity. 



The object of the present communication is to record the results of 

 certain researches on Plague Immunity which have been carried out in 

 the Plague Department of the Lister Institute. 



The chief problems dealt with in this contribution may be arranged 

 as follows : — 



1. Does the B. pestis produce a toxin capable of demonstration and 



suitable for experimental purposes ? 



2. If such a toxin is obtainable, does its injection into the animal 



body result in the production of an antitoxin, and in how far 

 does the ordinary anti-plague serum, which undoubtedly 

 confers protection on such animals as rats and mice, owe its 

 immunising property to an antitoxic action ? 



3. By what mechanism does an anti-plague serum exercise its anti- 



infectious effect ? 



It is unnecessary here to enter into all the details of the methods of 

 preparing anti-plague serum, but for the sake of clearness in discussing 

 certain of the questions connected with the above problems it seems 

 desirable to give a brief outline of the subject. 



As will be readily understood the most rigid precautions are necessary 

 to obviate the risks of infection during the process of immunisation. 



The ordinary procedure for obtaining an anti-microbial serum is 

 employed. The animals first undergo a course of intramuscular, or 

 intravenous, injections of killed cultures of the bacilli, till a certain degree 

 of immunity is acquired. In the case of the plague bacillus this pre- 

 liminary stage in the immunisation occupies a considerable period, 

 extending from four to six months, or even longer, the slow absorption of 

 the oedematous and indurated swellings which result from the sub- 

 cutaneous and intramuscular inoculations being chiefly responsible for 



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