THE BACTERIA IN NATURAL WATERS 21 



made in the midsummer of 1906 showed positive 

 results in 7 per cent of the samples of water entering the 

 storage reservoir and in 27 per cent of the samples 

 leaving it. The storage period in this case was about 

 two days and the temperature of the water in the 

 reservoir was nearly at blood heat (Harrisburg, 1907). 

 Clemesha (1912^) has recently made an exhaustive study 

 of this multipHcation of coU-like microbes in warm 

 waters and has shown that it is confined to certain 

 particular t>'pes within the colon group. For most 

 intestinal bacteria the conditions necessary for growth 

 and multiplication are not realized in water and an 

 entirely different temperature effect is manifest. When 

 a bacterium cannot multiply, the only vital activity 

 which can take place is a katabolic wasting away, 

 which soon proves destructive, and the higher the 

 temperature the more rapidly the fatal result is reached. 

 A frog in winter lives at the bottom of a pond breath- 

 ing only through its skin and eating not at all, but as 

 soon as the temperature rises it must eat and breathe 

 through its lungs or perish. It is quite true that even 

 in ice 40 per cent of typhoid baciUi perish in 3 hours 

 and 98 per cent in 2 weeks (Sedgwick and Winslow, 

 1902). Recent work has shown, however, that they 

 die in spite of the cold, not on account of it, and that 

 the decrease is more rapid at higher temperatures, 

 unless of course food-supply and other conditions admit 

 of multiplication. Houston (191 1) has furnished a 

 very clear demonstration of this temperature rela- 

 tion by storing typhoid bacilli in water with the results 

 tabulated on page 22. 



