180 APPLIED BACTERIOLOGY 



after five days — the difference in liability to attack is very 

 marked, the inoculated living in the same houses in Cal- 

 cutta being twenty times safer from attack and eighteen 

 times securer from death should cholera enter the house. 

 This is protection of a very decided character.' No cases 

 of cholera occurred among those who subjected themselves 

 to both inoculations. We must, however, bear in mind 

 that any person who has been persuaded to adopt this 

 prophylactic measure is probably well informed on the 

 subject of cholera, and fully alive to the wisdom of boiling 

 drinking-water and avoiding uncooked vegetables, and may, 

 therefore, be in the habit of using precautions neglected by 

 the majority. 



Preparation of Anticholeraic Vaccine. — The object of this 

 treatment is the acclimatisation of the system to a greater 

 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 



