BACTERIA IN WATER 181 



bination with other elements in chemical union, is inimical 

 to pathogenic non-spore-forming bacteria. 



In this book a word may be useful as to the means of 

 artificially purifying water for domestic purposes. For the 

 community water is purified by settling in reservoirs, or by 

 filtration through sand and stones, sometimes aided by the 

 addition of chemicals. For household purposes bacteria in 

 water may be removed by house filters made of porcelain 

 attached to the house supply, or what is better, .by boiling. 

 Domestic filters must be taken care of by some one thor- 

 oughly familiar with their operation and cleaning, otherwise 

 they do not deliver safe water. The flat taste of boiled water 

 may be removed by allowing air to go through by pouring 

 from one container to another several times. 



Water in a shallow vessel, preferably of copper, will be 

 practically sterilized by an hour's exposure to direct sunlight. 

 This is practicable for camping parties who are compelled 

 to use water under suspicion. Drinking water for companies 

 of troops on march is supplied by filling a large canvas bag 

 with any reasonably good looking water and adding calcium 

 hypochlorite. This ensures, after standing a short time, a 

 supply free of organisms dangerous to man. Canteens are 

 filled from faucets on the bag. 



Principal Water-borne Diseases. The principal diseases 

 transmitted by water are typhoid, cholera, and dysentery. 

 Typhoid bacilli may live in water, especially if surrounded 

 by a bit of protective and nutrient organic matter, for many 

 weeks. The question is often asked as to how a few germs 

 in a glass or two of water can cause typhoid fever. As a 

 matter of fact, when an epidemic of typhoid is starting there 

 are usually supposed to be many germs and not a few in the 

 water. What probably happens is that a small particle of 

 organic matter, possibly feces, is swallowed. This may 

 contain many thousand organisms. 



Although cholera organisms live in water a shorter time 

 than typhoid bacilli, they are said to be viable for several 



