BACTERIA IN WATER 



49 



properly filtered water. Hence the following has been 

 recognised more or less as the standard : 



o- loo bacteria per cc. =a good potable water. 



lOO- 500 " " = a suspicious water. 



500-1000 or more " =a water which should have 



further filtration before 

 being used for drinking 

 purposes. 



The personal view of the writer after some experience of 

 water examination would favour a standard of " under 500 " 

 being a potable water, if the 500 were of a nature indicating 

 neither sewage pollution nor disease. Miquel holds that not 

 more than ten different species of bacteria should be present 

 in a drinking water, and such is a useful standard. The 

 presence of rapidly liquefying hdiCt&xid. associated with sewage 

 or surface pollution would, even though present in fewer 



WolfhOgel's Counter 



numbers than a standard, condemn a water. Thus it will 

 be seen that it is impossible to judge alone by the numbers 

 unless they are obviously enormously high. 



When we are counting colonies upon a Koch's plate, 

 WolfhugeVs counter may be used. This is a thin plate of 

 glass a size larger than Koch's plates, and upon it are 

 scratched squares, each square being divided into nine 

 smaller squares. The Wolfhiigel plate is superimposed 



