30 HUMAN AND ANIMAL WASTES 



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-Typhoid Group of Bacteria 



Frankland (293, 294) was the first to establish that Eherthella ty- 

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

 water for 20 to 51 days although it dies out in 9 to 13 days in unsterile 

 surface water. In other studies (481) it was found that the typhoid or- 

 ganism was 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 apparently being responsible for 

 the destruction of the pathogen. These conclusions were later con- 

 firmed. Freshly isolated cultures of E. tyfhosa survived a shorter time 

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

 structive than low ones. Sedgwick and Winslow (846) reported that 

 cells of E. coli rapidly died 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, much longer in sterile soil. S. Martin (623), for example, 

 observed that typhoid bacteria survived and grew readily in sterile 

 soil but when added to well-moistened and cultivated soil they were 

 rapidly destroyed. The same phenomenon occurred when the patho- 

 gens 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 decomposition taking place 

 in the soil. It was further concluded that an antagonistic relation ap- 

 pears to exist in some soils but not in others and that this is due to the 

 action of specific antagonistic bacteria present in the particular soils. 



Frost (303) also reported that typhoid bacteria were rapidly de- 

 stroyed when added to the soil. In 6 days, 98 per cent of the cells were 



