0:^) 



MICRO-ORGANISMS IN WATER 



amined. The following experiments are selected, and 

 may be regarded as typical : — 



Description 



River Thames as supplied by the G-rand 



Junction Co. 

 River Thames as supplied by the 



Lambeth Co. 



Number of colonies obtained from 

 1 c.c. 



Day after 



collection 



Standing 



5 days in 



dark at 



20° C. 



Standing 

 27 days 



in dark at 

 20° C. 



4,894 I 15,950 

 2,587 I 6,980 



3,757 

 2,749 



The micro-organisms in these filtered waters multi- 

 ply, therefore, at 20° C. with far greater rapidity than 

 those in the unfiltered waters, which, as already pointed 

 oat, have rather a tendency to become diminished, mi- 

 less raised to the temperature of the incubator. The 

 following experiments again show the effect of placing 

 these filtered waters in the incubator for one night : — 



Description 



Number of colonies 

 obtained from 1 c.c. 



Day of 

 collection 



River Thames as supplied by the Chelsea Co. 

 Ditto Lambeth Co. . ... 

 Ditto Grand Junction Co 



305 

 265 

 208 



standing 

 through, 

 night in 

 incubator 

 at 37=' C. 



62,483 

 44,289 

 22,842 



Thus, at the temperature of the incubator, the mul- 

 tiplication which takes place during a single night is 

 enormous. 



Experiments were also made to ascertain the effect 

 of placing these filtered waters in a refrigerator for 

 a week, and the following examples illustrate this 

 point : — 



