214 APPLIED BACTERIOLOGY 



amount of the cholera poison than it would be likely to be 

 exposed to under ordinary circumstances. The treatment 

 is prophylactic, not remedial, as is the case in the serum 

 treatment of diphtheria. Haffkine uses two vaccines, the 

 first being an ' attenuated ' culture, produced by growing 

 the cholera spirillum in broth at a temperature of 39° C, 

 in flat-bottomed flasks, supplied with a current of sterilised 

 air. Grown in this way, the bacilli become ' attenuated,' 

 and may be grown repeatedly on nutrient media without 

 regaining their virulence. 



This vaccine is used first, 1 cubic centimetre being injected 

 into each person, and five days are then allowed to elapse 

 for it to exert its full effect. This prepares the subject for 

 the second dose of an ' exalted ' virus — that is to say, a 

 culture which, so far from being ' attenuated,' has had its 

 virulence intensified by being passed through a series of 

 animals. 



The cultures of both the ' attenuated ' and the ' exalted ' 

 virus are not either sterilised or filtered, but both the 

 living bacilli and their products are injected together. 

 There is no danger of imparting cholera by this pro- 

 cedure, as the cholera bacilli cannot live in the blood. 

 Both vaccines may, if desired, be carbolised, in which case 

 they will be sterile; but their power is unimpaired, and 

 they may be preserved indefinitely in sealed tubes. 



