350 WATER BACTERIOLOGY 



would probably be without effect upon the health of the individual. 

 The compound, chlorazene (p-sulphondichloraminobenzoic acid- 

 C^NC^SCelliCOOH), is excreted in the urine as p-sulphonamido- 

 benzoic acid. 



Ice. It is often the case that water which one would not con- 

 sider fit for drinking is used in the manufacture of ice. This 

 should not be the case as the freezing of water reduces only slowly 

 the number of organisms present. In fact Keith considers that 

 low temperatures alone do not destroy bacteria. On the contrary, 

 cold appears to favor longevity doubtless by diminishing destructive 

 metabolism. 



Probably the decrease in number is due to mechanical rupturing 

 of the cell, lack of oxygen, food and moisture which are due to 

 the low temperature. Although there is a decrease of bacteria, 

 yet experiments have demonstrated that even the pathogen Bacillus 

 typhosus may persist in ice for one hundred days. The cholera 

 vibrio perish much sooner. Hence, the evidence is conclusive 

 that just as pure a water should be used in the manufacture of 

 ice as is required in domestic supplies. 



