ISO PRACTICAL BACTERIOLOGY. 



organic material than that which has been contamin- 

 ated by organic matter from drains, etc., yet in spite 

 of this, the bacteria multiply much more rapidly in 

 the latter, which is richer in nourishment than in 

 the former, and in addition a large number of kinds 

 develop in the drain water, which cannot live in the 

 peat water. 



Thus, at the outset, we are in a position, in the 

 greater number of cases, to determine, according to 

 the number of kinds present in the water, whether its 

 organic impurities are the products of human habita- 

 tions, or whether they proceed from other less dan- 

 gerous sources, and it is now to be explained how 

 this knowledge may be utilised in the hygienic 

 analysis of drinking water. 



Very frequently the aim of the examination is to 

 determine if a certain definite pathogenic organism, 

 generally the typhoid bacillus, is present in the water 

 or not. Now, although it cannot by any means be 

 stated that it is impossible to demonstrate the typhoid 

 bacillus in water, for indeed it has been accomplished 

 in a few cases, yet it is only possible under especially 

 favourable circumstances, for a thousand samples of 

 water, which is suspected of containing typhoid 

 germs, may be examined with hardly a single success- 

 ful result. The explanation of this is simple. When 

 typhoid bacilli, by some means or other, first get into 

 the water, they are not evenly distributed throughout 



