QUALITATIVE BACTERIOLOGICAL ANALYSIS. 113 



pollution. Nevertheless, and as far as can be seen at present, it 

 not only equals, but far exceeds any known test, chemical or 

 bacteriological, for inferring the wholesomeness or otherwise of 

 a drinking water." Klein and Houston examined eight 

 specimens of sewage as to the total number of microbes, the 

 number of B. coli, and the number of spores of virulent 

 B. enteritidis contained in 1 c.c. of the fluid. Some of their 

 results are given in the following table : 



From this table it appears that there is no definite relation 

 between the total number of bacteria and the number either of 

 B. coli or of spores of B. enteritidis ; also there is no parallelism 

 between the number of B. coli and the number of spores of 

 B. enteritidis. It is also evident that to detect this organism 

 in a polluted water it may be necessary to resort to " the filter 

 brushing method," and to concentrate the water to small bulk. 

 Unless the pollution is very great, i.e., a dilution of sewage 

 less than 1-1000, it may be impossible to detect B. sporogenes 

 in 1 c.c. of a water polluted with sewage containing even 

 2000 spores per c.c. But as some specimens of sewage 

 contain only from 30-35 spores per c.c., a considerable 

 quantity of the water must be examined in order to detect the 

 B. enteritidis. As a matter of routine, it would seem advisable 

 to concentrate always at least 2000 c.c. of a polluted water, 

 by pumping through a Pasteur's filter, and diffusing the deposit 

 in 5 c.c. of sterile water. One c.c. of this should be added 

 to each of five milk tubes, which are then heated to 80 C. for 



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