CHOLERA, PLAGUE, TYPHOID FEVER 115 



December, 1896, in Calcutta, 7,908 persons were 

 inoculated, mostly in the cholera-stricken suburbs. 

 Cholera, later, visited 85 houses, in which protected 

 and non-protected persons were living together, and 

 1 ship, on which some of the crew were protected. 

 The total number of inhabitants in these houses, 

 and on this ship, was 1,395. Among the protected, 

 some had received only a preparatory " vaccine I." : 

 some had received both vaccine I. and vaccine II. 

 Among the latter, only one instance of failure was 

 observed : and that was 688 days after the date of 

 inoculation. 



Of the 85 houses, 5 must be left out of the 

 reckoning, because the proportion of protected 

 persons in them was less than 1 to 10 of the not 

 protected : thus, the escape of the protected might 

 be due to mere chance. (These five households 

 contained 161 not protected, 5 of whom were 

 attacked, and 7 protected, none of whom was 

 attacked.) That leaves 80 houses and 1 ship. 

 But, in 2 of the 80 houses, cholera broke out 

 twice : each of these houses thus comes twice into 

 the reckoning. That gives us 82 houses and 1 ship. 

 Here is Haffkine's comment on the table of cases 

 or, one ought to say, Nature's comment : 



" This table at once reveals the fact that the 

 incidence of cholera among the inoculated varied 

 according to three periods. During the first 4 days 



