BY OSCAR KATZ, PH.D., M.A. 913 



These figures yield, out of the 14 single cases, an average number 

 of 421 colonies in 1 ccm., and among these, 86 liquefying ones, 

 equal to 2O7 p.c. 



From the above table it will be seen that we have, as regards the 

 bacterial colonies, numbers before us which fluctuate within rather 

 considerable limits. The maximum of colonies enumerated was 

 2000 on August 4th, the minimum 23 on September 2nd. On Aug. 

 8th, the likewise enormous number of 1960 was obtained; twice 

 (Aug. 13th and 18th), 500 and 520 respectively. In five cases the 

 numbers oscillate between 100 and 200, whereas in only five cases 

 out of the whole were there less than 100 colonies. 



The amount of bacterial life in a given sample of water is, under 

 otherwise quite the same circumstances, greatly dependent on the 

 amount of organic matter suspended in it. In other words: the more 

 bacteria in the water, the greater the amount of organic matter in it. 

 Now it is worth notice that the numbers 2000, 1960, 500, 520, as 

 stated above, were obtained on days which succeeded a period of 

 rather heavy rain. This rainfall carried or washed into the supply 

 (dams) a certain quantity of crganic detritus along with the accom- 

 panying micro-organisms, and, after a time, the consequences of this 

 addition to the pipe-water made themselves evident by an enormous 

 increase in the quantity of bacterial colonies. The water under 

 examination then improved again vastly, as is well seen in all the 

 remaining cases (see above). 



From this also it follows that a general judgment of any water, 

 with reference to its contained bacteria, cannot be arrived at by 

 one single test, made on one or another day. Such an isolated 

 experiment will give us nothing but a rough idea of the condition 

 of the water for a limited time, and is not to be generalised. Even 

 the above 14 individual cultivations have to be multiplied, in order to 

 get more correct and reliable average numbers which would admit 

 of even a general verdict. 



As regards the relation between the quantity of bacteria present 

 in a given water, and its quality from a sanitary point of view, as 



