Bacteriological Examination. 



179 



the chlorine and the albuminoid ammonia showed no 

 correspondence with the bacteriological results. 



Vincent (Vihcent, 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 subsequent history is indi- 

 cated in the table below. 



PROGRESSIVE POLLUTION OF A WELL. 

 (VINCENT, ipos.) 



Bacteria i 

 per c.c. 



Bacillus Coli 

 per c.c. 



Before arrival of troops 

 6 days after arrival . . 

 14 days after arrival 

 41 days after arrival 

 60 days after arrival . 



200 



770 



4240 



6966 



14,900 



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, that a water could contain the typhoid 

 bacillus without giving clear evidence of pollution in the 

 dextrose-broth tube or on the lactose-agar plate. 



In the examination of springs, especially those used for 

 domestic supplies at country houses, the authors haye 



