Water and Ice 185 



been shown by bitter experience that the use 

 of the water may give rise to serious acute 

 disorders of the digestive system. Cholera 

 morbus and the so-called winter cholera are 

 apparently sometimes caused in this way. 

 Young children are especially susceptible to 

 the bad influences of such water, and the 

 boiling of it, or the change of supply, has 

 repeatedly been found sufficient to stop attacks 

 of cholera inf antum or the summer diarrhoea of 

 young children. 



On the whole, however, the bacteria which 

 water naturally contains as it is found in 

 lakes, running streams, and good springs are 

 usually quite harmless. 



The frequent real and serious dangers from 

 impure drinking-water do not lie in the bacte- 

 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 



