BACTERIA IN WATER 



47 



speaking, as regards many of the pathogenic bacteria, this 

 test is the most reliable of all. Nor would any responsible 

 bacteriologist be justified in certifying a water as healthy for 

 consumption by a large community if he was in doubt as to 

 the disease-producing action of certain contained organisms. 

 By working through some such scheme as the above we 

 are able to detect what quantity and species of organisms, 

 saprophytic or parasitic, a water or similar fluid contains. 



TYPES OF LIQUEFACTION OF GELATINE 



For, observe what information we have gained. We have 

 learned the form (whether bacillus, micrococcus, or spirillum), 

 size, consistence, motility, method of grouping, and staining 

 reactions of each micro-organism ; the characters of its culture, 

 colour, composition, presence or absence of liquefication or 

 gas formation, its rate of growth, smell, or reaction; and 

 lastly, when necessary, the effect that it has upon living 

 tissues. Here, then, are ample data for arriving at a satis- 

 factory conclusion respecting the qualitative estimation of 

 the suspected water. 



