32 HUMAN AND ANIMAL WASTES 



In order to illustrate the fate of certain important disease-producing 

 bacteria which find their way into the soil or into natural water basins, it 

 is sufficient to draw attention to reports of experiments made on a few 

 typical pathogens. 



The Colon-Tyfhoid Grouf of Bacteria 



Frankland (295, 296) was the first to establish that Eberthella ty- 

 -phosa may survive in sterilized polluted water or in pure deep-well 

 water for 20 to 5 1 days although it died out in 9 to 1 3 days in unsterile 

 surface water. In other studies (464) it was found that the typhoid or- 

 ganism is able to survive in sterilized tap water for 15 to 25 days, as 

 against 4 to 7 days in fresh water j the bacteria died off even more rap- 

 idly in raw river or canal water, the survival time being reduced to i to 

 4 days. The degree of survival of the typhoid organism in water was 

 found to be in inverse ratio to the degree of contamination of the water, 

 the saprophytic bacteria in the water being apparently responsible for 

 the destruction of the pathogen. These conclusions were later confirmed 

 (777). Freshly isolated cultures of E. tyfhosa survived a shorter time 

 than laboratory cultures, higher temperatures (37° C.) being more de- 

 structive than lower ones (438). Although some investigators (1007) 

 claimed that E. coli may survive in soil for 4 years, others (789) found 

 that it disappeared rapidly. Viable typhoid bacteria were recovered 

 (774) from polluted soil after lOO days in unsterilized soil, and after 

 16 months in sterilized soil. Sedgwick and Winslow (811) reported 

 that cells of E. coli rapidly die out in the soil, 99 per cent destruction 

 occurring in dry soil in 2 weeks, with a longer survival in moist soil. 



In general E. tyfhosa is able to survive only a short time in unsteri- 

 lized soil, but much longer in sterile soil (831). S. Martin (586), for 

 example, observed that typhoid bacteria survived and grew readily in 

 sterile soilj however, when added to a well-moistened and cultivated 

 soil they were rapidly destroyed. The same phenomenon occurred 

 when the pathogens were added to a culture of a soil organism in a 

 nutrient medium. Only in certain soils were conditions favorable for 

 the prolonged survival of the pathogen. The conclusion was reached 

 that the typhoid organism is destroyed by the products of decomposi- 

 tion taking place in the soil. It was further concluded that an antagonis- 



