PREVENTIVE INOCULATION. 241 



Owing to the consumption of water from the ponds or tanks belonging 

 to these villages, the inhabitants of the bustees are subject to periodic 

 visitations of cholera. It was in one of these bustees that the first 

 observation was made as to the effect of the cholera vaccines. 



The spring is essentially the cholera season in Calcutta. About the 

 end of March two fatal cases of cholera and two cases of choleraic 

 diarrhoea occurred in Katal Bagan Bustee, in a population grouped 

 around two tanks. This outbreak led to the inoculation of one 

 hundred and sixteen persons in the bustee out of about two 

 hundred. After the inoculation there occurred nine more cases of 

 cholera, seven of which proved fatal, and one case of choleraic diar- 

 rhoea. All the ten cases occurred among the uninoculated portion of 

 the inhabitants, which formed the minority, none of the inoculated 

 suffering. The results were more interesting when analyzed in detail. 

 Some of the cases had occurred in families in which some of the mem- 

 bers had been inoculated and others not, and the disease selected the 

 non-inoculated members, sparing the inoculated. Thus, in one house 

 six members out of eight had been inoculated. The attack, a fatal one, 

 occurred in one of the remaining two. In another house eleven mem- 

 bers out of eighteen were inoculated. The eleven members remained 

 free while four out of seven not inoculated were attacked. 



Upon these observations the Calcutta municipality felt encouraged 

 to vote funds for the continuance of the inoculations in an experi- 

 mental farm, and appointed for that purpose a special staff. In 1896 

 the result of two years' observations were embodied by the health 

 officer in a report to the Calcutta Municipal Corporation. It recorded 

 a most satisfactory state of affairs. During the time under observation 

 some eight thousand persons were inoculated. Cases of cholera oc- 

 curred in seventy-seven huts in which some members of the family 

 had been previously inoculated and others not. Comparing the inci- 

 dence of the disease in the two groups, a striking advantage was found 

 to be with the inoculated. I made an analysis of the cases according 

 to the time which had elapsed between inoculation in each of these huts 

 and the occurrence of cholera in them, and the following results were 

 found. During the first four days after inoculation, apparently before 

 the vaccine had time to produce its full protective effect, there were 

 proportionately 1.86 times fewer deaths among the inoculated than 

 among the non-inoculated members of the families. In a second period, 

 extending from the fifth to the four hundred and twenty-ninth day — 

 i. e., for fourteen months — there were 22.62 times fewer deaths among 

 the inoculated; while in the last period — that is, between the four 

 hundred and thirtieth and seven hundred and twenty-eighth day after 

 the inoculation — there were only 1.54 fewer deaths among the inocu- 

 lated, the immunity having evidently gradually disappeared. The net 



VOL. LVII.— Ifi 



