The Colon Bacillus 75 



by hosts of other bacteria whose presence is inimical 

 to the survival of the colon bacillus. 



The examination of soils of different origin has 

 demonstrated that in those not recently manured the 

 colon bacillus is present in slight numbers or not at all. 

 On the other hand, greater numbers were found in soils 

 that had recently received applications of horse-manure, 

 but the tendency for their gradual decrease was observed 

 here also. Soils which were experimentally inoculated 

 with this organism, were not found, on the whole, to 

 be favorable to its development. It is not, apparently, 

 able to withstand the competition of bacteria normal to 

 cultivated soils, and, while in exceptional cases, it may 

 even increase to a slight extent, its gradual decrease in 

 numbers is inevitable. Water bacteriologists, therefore, 

 agree, for the most part, that the presence of large num- 

 bers of the colon bacillus is a certain indication of recent 

 pollution with sewage. 



Taking the foregoing facts in their entirety, we 

 find, therefore, that the colon bacillus is present in enor- 

 mous numbers in the excreta of man and of domestic 

 animals; that it is present in large numbers in sewage 

 because this contains human and animal wastes; that 

 it is not present in ordinary soils, except occasionally, 

 or in slight numbers. We are thus forced to the conclu- 

 sion that our surface waters, used for drinking purposes, 

 do not receive large numbers of the colon bacillus from 

 the soils with which they come in contact. The presence 

 of these organisms in surface waters must indicate' 

 either recent sewage contamination, or the possible 

 piultiplication of the colon bacillus in the water itself. 



