118 THE STORY OF THE BACTERIA. 



ria which naturally occur there at all, but in 

 those which get into it from outside, through 

 pollution by the waste from animals and 

 human beings, and especially from human 

 beings who are the victims of some bacterial 

 disease. 



Polluted water may convey the bacteria 

 which cause Asiatic cholera, and the same is 

 true for diphtheria or the wound diseases, 

 and doubtless many others, but the spread of 

 these latter diseases in this way is no doubt 

 quite infrequent. 



It is typhoid fever, whose germs, of all 

 those which cause disease, are, so far as 

 we now know, most apt to be spread by pol- 

 luted water. The discharges from persons ill 

 of typhoid fever, thrown without disinfection 

 into the vaults of country or village out-houses, 

 which, in an appalling number of cases, are 

 in direct communication, through underground 

 channels, with the wells, or with springs from 

 which the farmer supplies the family or guests, 

 may pass, with but a very moderate dilution, 

 into the digestive tracts of the unsuspecting 

 victim. It is ignorance, not Providence, which, 



