On Preventive Inoculation. 



255 



In the vast majority of cases there lived in the same families 

 members who had not been inoculated, together with others inoculated, 

 and the possibility thus presented itself of comparing the incidence of 

 the disease in individuals of the same households, exposed as much as 

 it is possible to the same chances of infection. 



During the time under observation cases of cholera occurred in 

 seventy-seven huts. The interval which elapsed between the applica- 

 tion of inoculation in each particular hut and the occurrence of cholera 

 in it was as follows : — 



Among uninoculated members of the families cholera occurred — 1, 2, 

 3, 4, 5, 6, 9, 12, 13, 15, 17, 22, 34, 37, 44, 57, 62, 63, 71, 95, 99, 

 109, 114, 118, 119, 120, 129, 132, 139, 143, 162, 189, 191, 203, 240, 

 251, 271, 281, 284, 300, 309, 318, 319, 334, 356, 359, 362, 370, 

 372, 378, 383, 384, 389, 391, 393, 394, 401, 404, 408, 416, 433, 446, 

 448, 453, 472, 493, 498, 673, 720, 723, 724, and 738 days after the 

 inoculation of the other members of these families. Among the 

 inoculated members of the families cholera occurred — 0, 2, 3, 4, 219, 

 421, 459, 512, 688, 735, and 738 days after their inoculation. 



Thus for a period of 738 days, cases of cholera occurred among 

 the uninoculated, so to say, at all intervals after the date of inocula- 

 tion ; whereas the figures referring to the inoculated showed a striking- 

 variation of the incidence when compared at various distances from 

 the time of inoculation. Cases continued to occur among the 

 inoculated for a period of four days after the treatment, and then for 

 416 days they practically remained free from the disease, only one 

 death from cholera having occurred among them during that time. 

 From the 421st day up to the end of the observations six cases occurred 

 among them again. 



The relative immunity in the inoculated considered separately 

 during those three periods shows that during the first four days the 

 inoculated had proportionately T86 times fewer deaths from cholera 

 than the uninoculated. 



During the period between the 5th and 420th days, i.e., for a period 

 of nearly fourteen months, the number of deaths among the inoculated 

 was 22-62 times smaller than amongst the uninoculated. And for the 

 rest of the time under observation the proportion in their favour fell 

 to 1 to 1-54.* The plan has since been formed of trying the effect 

 of larger doses and of stronger vaccines, in order to obtain a more 

 lasting protection. 



While thus the absolute number of cases and deaths from cholera 

 appeared so strikingly influenced by inoculation, the peculiarity that 

 became apparent from the observations in Calcutta as well as in other 



* Vide Health. Officer's Report to tlie Chairman of the Calcutta Municipal Cor- 

 ^oration, reprinted, in the ' Indian Medical Gazette,' toI. 31, No. 8, August, 1896. 



