BACTERIOLOGICAL EXAMINATION 225 



ing the spring; but the same conditions might easily 

 have led to infection from human beings. 



Fromme (1910) cites several interesting examples 

 of temporary pollution detectable only by bacteri- 

 ological tests. The most striking case was that of an 

 artesian well. Its average bacterial content had been 

 38 per c.c. and colon bacilli were absent from 200 c.c. 

 In May, 1908, this well became polluted from a broken 

 stable drain 10 meters away. The number of bacteria 

 rose to 4370 and colon bacilli were found in 10 c.c. sam- 

 ples. The source of pollution was removed, but the 

 well water in July still contained 7100 bacteria and B. 

 coli in I c.c. In September the number had fallen to 

 105 and colon bacilli were present in 200 c.c. In Novem- 

 ber the bacteria numbered 120 and colon bacilli were 

 absent from 200 c.c. At no time did chemical tests 

 give any indication of danger, while the bacteriological 

 data obviously measured very delicately a comparatively 

 slight but real pollution and its gradual disappearance. 



Similar results have been reported by Savage and 

 Bulstrode (Savage, 1906) in the examination of the 

 water-supply of Bridgend. 



It seems to the writers that the real appUcation 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 bacteri- 

 ological tests will not serve, on account of their exces- 

 sive delicacy. In studying the heavy pollution of small 

 streams, the treatment of trades wastes, and the 

 purification of sewage, the relations of nitrogenous 

 compounds and of oxygen compounds are of prime 



