48 ELEMENTS OF WATER BACTERIOLOGY. 



than 8 per c.c. The highest individual counts obtained, 

 as will be seen by reference to the table on the preceding 

 page, were 95 in a meadow pool, 83 in a brook, and 74 

 in a barnyard well, the latter probably actually polluted. 

 Only two samples in the whole series, one from the well 

 above mentioned, gave any red colonies on the agar 

 plates. 



Thus it is clear that organisms growing at the body tem- 

 perature and those fermenting lactose are not numerous 

 in normal waters, the total count rarely exceeding 50, 

 with acid producers generally entirely absent. On the 

 other hand, the numbers on the litmus-lactose-agar plate 

 will be likely to run into hundreds with a good proportion 

 of red colonies when polluted waters are examined. The 

 method is, therefore, one of the most useful at the dis- 

 posal of the bacteriologist. It yields results within 

 twenty-four hours, and the conclusions to be drawn from 

 it are definite and clear. 



