BACTERIOLOGICAL EXAMINATION 



223 



genes, and streptococci. On the other hand, the chlorine 

 and the albuminoid ammonia showed no correspondence 

 with the bacteriological results. 



Vincent (Vincent, 1905) cites an interesting case of 

 the detection of progressive pollution of a ground- 

 water by bacteriological methods. The well of a 

 military camp in Algeria showed 200 bacteria per c.c. 

 before the arrival of a regiment of troops. Its sub- 

 sequent history is indicated in the table below: 



PROGRESSIVE POLLUTION OF A WELL 



(Vincent, 1905) 



Before arrival of troops 

 6 days after arrival . . . . 

 14 days after arrival . . . 

 41 days after arrival. . . 

 60 days after arrival . . . 



Bacillus coli per c.c. 



Thirdly, negative tests for Bacillus coli and low bac- 

 terial counts may be interpreted as proofs of the good 

 quality of water, with a certainty not attainable by any 

 other method of analysis. Many a surface-water with 

 reasonably low chlorine and ammonias has caused epi- 

 demics of typhoid fever; but it is impossible, under any 

 natural conditions (except perhaps in a well polluted 

 with urine) that a water could contain the typhoid 

 bacillus without giving clear evidence of pollution in the 

 bile tube or on the lactose-agar plate. 



In the examination of springs, especially those used 

 for domestic supplies at country houses, the authors have 

 found that the bacteriological examination offers a 



