BACILLUS PESTIS 379 



of a "sensitized vaccine" against plague. This consists of 

 dead pest bacilli (killed by heat) that have been mixed with 

 antiplague immune serum obtained from an artificially 

 immunized animal. It is claimed by him that the process 

 of sensitizing lessens the toxic action of the dead bacteria; 

 diminishes the risk run by injecting them and elimina,tes 

 the uncomfortable local and constitutional reactions that 

 so often accompany the injections; while at the same time 

 the protective properties of the "vaccine" are preserved. 

 Rowland,^ in a critical review of the subject, fails to find 

 any neutralization of the toxic properties of the dead bacteria 

 through sensitization, but states that Besredka's "vaccine" 

 possesses good immunizing power and users of it have 

 reported favorably as to the minimum of discomfort fol- 

 lowing its inoculation. The principle here used has been 

 applied by Besredka, Gay and others to the making of pro- 

 tective agents for other types of infection. 



Antiplague Serum. — ^The general principles that are 

 involved in the induction of immunity with antibody 

 formation hold for plague as for a number of other types 

 of infection; that is to say, the repeated injection into 

 animals of non-fatal doses of the specific organism or the 

 products of its growth, results in the elaboration in the 

 injected animal of substances that are in one way or another 

 antidotal, destructive or neutralizing for the matters injected. 



In the effort to secure specific antiplague serum two 

 general plans have been followed: one, by the repeated 

 injection of horses with at first increasing doses of dead 

 pest bacilli followed by ascending doses of the living organ- 

 ism (Yersin's method);^ the other by the injection of the 



' Journal of Hygiene, Plague Supplement II, 1912, p. 344. 

 " Annales de I'lnstitute Pasteur, 1897, p. 81. 



