126 THE STORY OF THE BACTERIA. 



germs, the disease-producing forms among 

 the rest. 



Filtration on the large scale in properly 

 arranged systems appears to be the only reli- 

 able way of freeing contaminated water 

 mechanically from its bacterial ingredients. 



Thorough boiling of water for at least an 

 hour will, however, kill the bacteria, and to 

 this, in the last resort, the householder must 

 have recourse when the water supply is justly 

 suspected to be causing and fostering disease. 

 This purification of water by boiling may be 

 done by the householder himself, or, if he can 

 afford it, he may supply himself with the dis- 

 tilled and aerated water which is now furnished 

 in many towns. 



But, after all, when the facts about the dan- 

 gers of a polluted water supply become gener- 

 ally known, it ought not to be necessary for 

 the householder to adopt any domestic pre- 

 cautions against water infection in towns or 

 cities. If politics, or private or corporate 

 greed, or general ignorance or apathy stand 

 in the way of sanitary reform, the outlook for 

 the water consumer is indeed not encouraging, 



