viii.] THE INFECTIVENESS OF CHOLERA. 149 



the habits of the poor, the water-supply, the abundance of 

 filth, all combine to make them a good breeding-ground ; 

 the comma-bacilli are known to multiply with enormous 

 rapidity, they have been proved capable of growing and 

 multiplying in almost everything that contains animal 

 and vegetable matter, and yet no cholera epidemic 

 seems to result. The effective method adopted in India 

 of moving the troops out into camp and away from a 

 locality in which cholera has broken out proves the same 

 fact. Often soldiers carry infection into such a camp, are 

 there taken ill with cholera, yet with such exceptions 

 no other cases occur. Millions and millions of comma- 

 bacilli are present in camp, still they do not produce 

 infection. 



The same holds good with regard to season. A few 

 cases of cholera occur in Calcutta all the year round ; there 

 is hardly a month in the year in which isolated cases do not 

 occur. Yet anything like an epidemic is unknown between 

 June and December. The number of cases begin to rise in 

 December, about Christmas time, steadily go on increasing 

 till March and April, then decrease again. The comma- 

 bacilli are available all the year round ; the habits of the 

 natives as regards the use of the water from the tanks for all 

 and every purpose remain the same all the year round. If 

 a case of cholera occurs, say in October, in one of the huts 

 or bustees surrounding a tank, the dejecta invariably find 

 entrance into the tank, for this is the natural sewer of the 

 huts ; along the shore of these tanks there is any amount of 

 decaying animal and vegetable matter, and there exists here 

 therefore a good and sufficient nutritive medium for the 

 comma-bacilli. In all tanks the natives of the bustees can 

 be seen at all times and seasons performing their external 

 and internal ablutions, washing their linen and their cooking 



