248 ORIENTAL PLAGUE chap. 



that is to say, the question of the degree of immunity 

 conferred by inoculation against infection, and to what 

 extent are agglutinating, antitoxic, and germicidal 

 substances to be met with in the blood of the injected 

 animal. 



All the points above enumerated require to be 

 elucidated before claim can be made to a fair under- 

 standing of the action of the prophylactic — before, that is, 

 a rule-of-thumb practice can be superseded by a scientific- 

 ally proved method of standardising and of using the 

 prophylactic. 



I now proceed to describe the experiments and 

 observations which have been undertaken towards the 

 elucidation of some of these matters. 



The Preparation of Hajfkine Plague Prophylactic. 

 — The fluid which Haffkine [Proceedings, Royal Society, 

 June 1900) prepares for distribution and transmission is 

 a broth culture of B. pestis incubated for four to six 

 weeks, and then sterilised at 65-70° C. for one hour. It 

 is next decanted into and preserved in special bottles, each 

 containing about 0*5 percent carbolic acid. 1 The prophy- 

 lactic employed in the experiments to be recorded was in 

 most respects prepared like Haffkine's broth culture, with 

 addition, that is, of a few drops of sterile clarified butter. 

 It was decanted into test tubes, each capable of containing 

 32-36 cc, which were then sealed and finally sterilised at 

 70° C. for one hour. No preservative, however, was 

 added. 



Haffkine has pointed out that different brews of 

 the prophylactic started from the same plague culture — 



j 



1 At present (1906) the prophylactic is preserved in Bombay without the 

 addition of preservative. 



