BACTERIOLOGICAL EXAMINATION. 115 



of a brook which had been formerly connected with the 

 pond was open at the bottom, although it was supposed 

 to have been shut, thus admitting a contaminated sur- 

 face-water to the supply." Whipple also calls attention 

 to the report on the Chemical and Bacteriological Exami- 

 nation of Chichester Well-waters by Houston (Houston, 

 1 901), in which the results of chemical and bacteriologi- 

 cal examinations of 30 wells were compared. It was 

 found that the bacteriological results were in general 

 concordant and satisfactory. The wells which were high- 

 est in the number of bacteria showed also the greatest 

 amount of pollution, as indicated by the numbers of B. 

 coli, B. sporogenes, and streptococci. On the other 

 hand, the chlorine and the albuminoid ammonia showed 

 no correspondence with the bacteriological results. 



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. 



It seems to the writers that the real application of 

 chemistry begins where that of bacteriology ends. When 

 pollution is so gross that its existence is obvious and only 

 its amount needs to be determined, the bacteriological 

 tests will not serve, on account of their excessive delicacy. 



