SPIRILLUM CHOLERA ASIATICS. 585 



the severity of the attack; for cases are recorded of 

 persons who were apparently not sick at all, and yet 

 in whom an acquired immunity was produced. How 

 long this immunity lasts is not positively known, but 

 probably for a month or more, so that the same person 

 is not likely to be taken ill again with cholera during 

 an epidemic. 



Within the last few years Haffkine, in India, has 

 succeeded in producing an artificial immunity against 

 cholera infection by means of subcutaneous injections of 

 cholera cultures. In over 200,000 persons whom he 

 has inoculated the results obtained would undoubtedly 

 seem to show a distinct protective influence in the pre- 

 ventive inoculations. And Kolle has found that the 

 blood-serum of persons inoculated by Haffkine' s method 

 gave a similar reaction to that of persons who had re- 

 covered from cholera. 



On the other hand, we may take it for granted that 

 susceptibility to cholera may be acquired or increased. 

 For instance, there is no doubt that gastric and intes- 

 tinal disorders produced by overeating, etc., may act 

 as contributing causes to the disease. Other predispos- 

 ing causes are general debility from poverty, hunger, 

 disease, etc. 



Varieties and Variations of the Cholera Bacillus. Cun- 

 ningham, as a result of researches made in Calcutta 

 (1891), arrives at the conclusion that Koch's comma 

 bacillus cannot be accepted as the specific etiological 

 agent in this disease: First, as in many undoubted cases 

 of cholera he has failed to find comma bacilli; second, 

 because in one case he found three different species; 

 and, third, because in one case the indol reaction could 

 not be obtained. Since Cunningham's investigations 



