DISEASE GERMS 85 



must be capable of and receive complete sterilization. 

 Any faucet filter which allows a generous stream of 

 water to issue quickly after it is turned on is practical- 

 ly useless so far as the removal of bacteria is con- 

 cerned. 



A suspected water or one of unknown quality would Filter 

 better be filtered and then boiled rather than boiled apd Bon* 

 filtered, if it needs to be filtered to remove suspended 

 matter. Distilled water or water turned into steam 

 and condensed is a pure water; but to remain so it 

 must be received into perfectly clean vessels and not 

 exposed to dust. 



Ice as ordinarily delivered frequently shows three Ioe 

 layers. One, usually at the top, the snow ice, is scarce- 

 ly transparent and when melted shows impurities not 

 visible in the ice. This usually holds many bacteria 

 and should always be rejected. Another layer, par- 

 tially transparent, is more or less bubbly. These 

 bubbles contain air which allows any living forms 

 therein to remain alive if not to grow. If derived 

 from impure water the bubbles may contain some 

 of the germs which will make the ice undesirable, 

 since many bacteria survive a lower temperature than 

 ice ever attains. A third portion is wholly trans- 

 parent. This last, the crystal clear ice, is the only ice 

 which should ever be used directly to cool drinking 

 water, for this alone is purified by crystallization al- 

 though not perfectly. 



Ice should always be washed from surface dirt before 



