34 HUMAN AND ANIMAL WASTES 



coccus, Flavobacterium, and yeast, 2 actinomycetes, and 3 unidentified 

 nonspore-forming, gram-negative rods (445). 



The survival of E. tyfhosa in manure and in soil is known to be re- 

 pressed decidedly by various saprophytic bacteria. When a carrier was 

 induced to urinate on a soil, E. tyfhosa could be recovered within 

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

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

 moist with the urine (616). 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. tyfhosa is destroyed by bacteria grown in 

 association with it (382). Moisture was found (785) 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 sur- 

 vival of the remainder extending over a period of months. 



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

 piles (623). The addition of 9 million cells of E. coli and 13 mil- 

 lion cells oi A. aerogenes to a soil resulted, in 106 days, in reductions to 

 6,000 and 25,000 respectively} in 248 days, both organisms had com- 

 pletely disappeared (828). The occurrence of coliform bacteria in soil 

 depends entirely on the degree of pollution ; soil relatively free from 

 pollution contains no coliform bacteria or only a small number. No evi- 

 dence of multiplication of these bacteria in the soil could be detected 



(873). 



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

 isms added to it (937, 1014). 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 1 2 and 1 6 hours, whereas 

 paratyphoid organisms survived for 21 and 23 days (887). Protozoa 

 were found to be at least partly responsible for the destruction of the 

 typhoid organism added to water systems (250, 440, 709, 815). 



Mycobacterium tuberculosis 



The fate outside the hosts of the bacteria causing tuberculosis in man 

 and in animals has also been studied extensively. Considerable diffi- 



