Temperature in Relation to Their Development 69 



with an equal amount of surface drainage in the summer, 

 the bacterial additions to the surface waters will be 

 much greater than those in the winter. 



In the water itself, on the other hand, the develop- 

 ment of the bacteria is more intense in the summer 

 than it is in the winter. This involves a more rapid 

 destruction of the organic matter and the corresponding 

 disappearance of the bacteria introduced from out- 

 side sources. In the winter, on the other hand, the 

 destruction of the organic matter is practically at a 

 standstill. Then -the outside bacteria do not suffer so 

 much from the competition of the normal water bacteria, 

 for both are quiescent, and the reduction in the total 

 number of bacteria is not favored to such an extent. 

 This view is encouraged by a number of experiments 

 that show that typhoid germs disappear from unsteril- 

 ized water more quickly in summer than in winter. 



It is to be further noted in this connection that the 

 normal water bacteria, as well as the great bulk of soil 

 bacteria, develop easily at 68° to 72° Fahr. The bacterial 

 inhabitants of the intestinal tract of warm-blooded 

 animals, however, develop best at blood temperature. 

 It is but natural to expect, for this reason, that these 

 intestinal bacteria will find themselves at a disadvantage 

 when introduced into drinking-water in sewage or in 

 'other materials. These organisms actually perish within 

 a comparatively short time, owing largely to the com- 

 petition of the other bacteria. This competition, reacting 

 unfavorably on typhoid . germs and other intestinal 

 bacteria, may be regarded from two different stand- 

 points. 



