32 HUMAN AND ANIMAL WASTES 



6 hours from the washings of the soil j however, after 30 hours the or- 

 ganism could no longer be demonstrated, although the soil was still 

 moist with the urine (6s5). In the absence of sunlight, the organism 

 was recovered after 24 hours but not later. When the urine was allowed 

 to dry on towels, the bacterial cells survived for 10 days because sapro- 

 phytic microorganisms failed to develop on the dry towels. Other evi- 

 dence was submitted that E. ty-phosa is destroyed by bacteria grown in 

 association with it. Moisture was found to be the most important factor 

 influencing the longevity of typhoid bacteria in the soil j 50 per cent of 

 the bacteria died during the first 48 hours, the survival of the remainder 

 extending over a period of months. Even in those investigations where 

 E. typhosa was detected after 70 or 80 days, the evidence pointed to a 

 lack of multiplication of these bacteria in the soil 5 when the organism 

 survived for a shorter time in sterilized than in natural soil, it was 

 found (616) to be due to the fact that steam heating of soil results in 

 the formation of bactericidal substances. 



E. colt was rapidly crowded out by other organisms in manure 

 piles. The addition of 9 million cells of E. colt and 13 million cells oi A. 

 aero genes to a soil resulted, in 106 days, in reductions to 6,000 and 

 25,000 respectively J in 248 days, both organisms had completely dis- 

 appeared (856). The occurrence of coliform bacteria in soil depends 

 entirely on the degree of pollution j soil relatively free from pollution 

 contains no coliform bacteria or only a small number. No evidence of 

 multiplication of these bacteria in the soil could be detected (899). 



Sea water, as well, appears to have a bactericidal effect upon organ- 

 isms added to it (959, 1050). This is believed to be due to the presence 

 of some substance other than salt. Dysentery and typhoid organisms 

 were found to disappear from sea water in 12 and 16 hours, whereas 

 paratyphoid organisms survived for 21 and 23 days (915). Harvey 

 (386) concluded that sea water contains a substance that is inhibitory 

 to the growth of diatoms j this substance is adsorbed on precipitated 

 phosphate or animal charcoal, and is destroyed by treatment with 

 H2O2. 



Protozoa were found to be at least partly responsible for the destruc- 

 tion of the typhoid organism added to water systems (452, 741). 



