ANTI-PLAGUE SERUM. 317 



Wyssokowitz and Zabolotny 1 call attention to the 

 fact that the blood of patients convalescing from plague 

 has an agglutinating action upon fluid cultures of the 

 plague bacillus analogous to that observed when the 

 blood-serum of typhoid or of cholera patients is mixed 

 with similar cultures of the typhoid or the cholera 

 bacillus. (See Agglutinins). 



PROTECTIVE INOCULATION ; VACCINATION : Immu- 

 nization from plague by vaccination has been variously 

 attempted. The method probably most widely practiced 

 is that of subcutaneous injection of dead cultures of ba- 

 cillus pestis. In India the method suggested by Haff- 

 kine has been tested on a comparatively large scale. This 

 vaccine, fairly representative of the group, consists of six 

 weeks old bouillon cultures of the organism that have been 

 killed by an hours exposure to 65 C. The subcutaneous 

 dose is from 0.5 to 3.5 c.c. according to the age and con- 

 dition of the person. It may be necessary to give two 

 or three such injections following each other after varying 

 intervals of a day or more. The injections are followed 

 by both local and constitutional reactions, after which 

 the person is more or less safe from infection with the 

 living organism. The immunity manifests itself soon 

 after the vaccination and persists for six weeks or 

 longer, varying with the individual. The statistics 

 of the Indian Plague Commission demonstrate that both 

 morbidity and mortality from plague are much less 

 among the vaccinated than among those not so protected. 



ANTI-PLAGUE SERUM. Yersin, Calmette, and Bor- 

 rel 2 have demonstrated that the general principles under- 



1 Annales de 1'Institut Pasteur, 1897, p. 663. 



2 Ibid., 1895, p. 589. 



