THE HAFFKINE VACCINE AGAINST PLAGUE. 325 



expressed more definitely than by the term bactericidal 

 serum. 



THE HAFFKINE VACCINE AGAINST PLAGUE. A 

 great deal of work has also been done in recent years 

 in conferring active immunity against bacillus pestis by 

 the Haffkine method that is, by the injection of dead 

 cultures of the organism, and also by the injection of 

 organisms of low degree of virulence, whereby an active 

 immunity is conferred. Especially satisfactory immuniz- 

 ing results have been obtained by combining the vacci- 

 nation with dead cultures or cultures of low virulence 

 with the administration of the immune serum. While 

 the vaccination is entirely harmless for animals suscep- 

 tible to bacillus pestis, even in large doses, the experi- 

 ments on human beings could only be carried out in 

 combination with the administration of the immune 

 serum or after previous injection of dead cultures. 



In 1897 Haffkine reported to the Indian government 

 that he had prepared an inoculation fluid for the protec- 

 tion of human beings against plague infection. This 

 fluid is now prepared by the Plague Research Labora- 

 tory in Bombay, and up to December, 1900, they had 

 distributed 1,628,696 doses. It has been found that 

 this fluid does not give the same degree of protection 

 against plague as does vaccinia against smallpox, but 

 the general results obtained in India indicate that the 

 individuals vaccinated with this material are not only 

 far less liable to infection by the plague organism, but 

 if they become infected they are more likely to recover. 



Bannerman, of the Plague Research Laboratory in 

 Bombay, gives several instances of the value of the 

 inoculation as a protection against plague infection, and 

 cites the personnel of the Southern Mahratta Railway, 

 which were as follows : 



