VIIL] THE INFECTIVENESS OF CHOLERA. 157 



every respect with those found in choleraic dejecta. Not- 

 withstanding their presence in this water, and notwithstand- 

 ing the extensive use the 200 families were constantly 

 making of it, there has been no outbreak of cholera. 

 Now we have in this instance an experiment performed by 

 nature on a scale large enough to serve as an absolute and 

 exact one. This water had been unquestionably and 

 notoriously contaminated with choleraic evacuations, and 

 therefore also with the comma -bacilli, and was used exten- 

 sively by many human beings for several weeks ; if we say 

 with Koch that the comma-bacilli were the cause and essence 

 of cholera, how is it that not one person amongst so many, 

 up to the middle of December and afterwards, contracted 

 the disease ? Clearly because the water did not contain the 

 active cholera virus, and because this latter cannot be 

 identical with the comma-bacilli. 



It might be said, and Koch has said so, as a matter of 

 course, in criticising my observations, that perhaps the 

 comma-bacilli present by the end of November were not the 

 same as the cholera-bacilli; but it must be remembered 

 that a case of undoubted cholera having here occurred, 

 owing to the conditions obtaining and owing to the habits of 

 the people, large quantities of comma-bacilli must of 

 necessity have been thrown and carried into this tank ; along 

 the shore the water contained abundance of decaying 

 animal and vegetable nitrogenous material to form a very 

 good and suitable nourishing medium for the bacilli, and 

 they must have had ample opportunity to multiply, and 

 consequently there must have been large numbers of them 

 present, sufficient for hundreds of human beings : neverthe- 

 less no case of cholera occurred. 



An equally striking illustration of the innocuousness of 

 the comma-bacilli is furnished by a tank situated near 



