THE MULTIPLICATION OF MICRO-ORGANISMS 239 



per c.c. was severity-three, whilst the largest figure 

 reached was 75,000 ; whilst in some cases so many 

 were present that they were impossible to estimate. 

 The seltzer-water prepared from filtered distilled water 

 contained larger numbers of bacteria than that from 

 plain distilled water, and it would appear that in the 

 process of filtration the water, instead of undergoing a 

 diminution in its bacterial contents, received an increase, 

 which was doubtless due to the filtering apparatus not 

 being sufficiently often cleansed and renewed. 



In the second series of experiments seltzer- water 

 prepared from distilled water only was examined. The 

 bottles were kept from one to fourteen days at a tem- 

 perature of from 10 to 15 C., with the exception of 

 one sample, which remained for one day in a warm room. 

 This seltzer- water was found to contain in the first 

 few hours after its preparation 118 microbes per c.c., 

 whilst after standing for fourteen days ninety-two or- 

 ganisms were found. As many as 2,260 were found in 

 the sample kept for one day in a warm room, which 

 may be ascribed to the higher temperature at which 

 it was preserved, and also to the possibility of a larger 

 initial number being present. 



There was a curious increase in the number of 

 moulds observed in the samples preserved during 

 several days. Owing to the extremely variable num- 

 ber of bacteria found in samples of seltzer-water from 

 one and the same source, it is difficult to ascertain what 

 was the exact effect of storage on their numbers, as for 

 each determination a different bottle of seltzer-water 

 had to be used. Thus, in the sample kept for nine 

 days 914 bacteria were found per c.c., being many 

 more than in the first sample only a few hours old, 

 which contained 118 per c.c. Again, the sample one 

 day old had sixty- three, whilst, as pointed out, the 



