SPIRILLUM CHOLERZ ASIATICH. 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 
