26 HUMAN AND ANIMAL WASTES 



do not maintain proper sanitation and because human excreta are used 

 as fertilizers. Any successful system for the control of these diseases 

 must be sanitary and at the same time profitable. Of 1,190 persons 

 examined, 81 per cent were positive for ascaris, with an average egg 

 count of 14,000 per cubic centimeter. Children had a higher count than 

 adults, and females a higher count than males. The life habits of the 

 Chinese people are highly favorable for the spread of ascaris. By a 

 special process of composting of feces, sufficient heat was produced to 

 destroy disease-producing organisms and their reproductive bodies. 

 The compost thus produced is highly effective as a fertilizer (1023). 



SURVIVAL OF HUMAN AND ANIMAL PATHOGENS 

 IN SOIL AND WATER 



During the period 1878 to 1890 following the brilliant work of 

 Pasteur, when bacteriology was still in its infancy, medical bacteriolo- 

 gists took much interest in soil microbes. This was due largely to the 

 belief that causative agents of disease that find their way into the soil 

 may survive there and thus become a constant and important source of 

 infection. The introduction by Koch, in i88i-, of the gelatin plate 

 method placed in the hands of the investigator a convenient procedure 

 for measuring the abundance of the soil population and determining the 

 survival in the soil of agents causing serious human diseases. In spite of 

 the fact that this method revealed only a very small part of the soil 

 population, it enabled the medical bacteriologist to establish beyond 

 doubt that such organisms tend to disappear in the soil. This resulted in 

 definite conviction on the part of the public health and medical world 

 that the soil is seldom a source of infection. It was soon demonstrated 

 that disease-producing agents die out in the soil at a rather rapid rate, 

 depending on the nature of the organisms, the soil, climate, and other 

 conditions. 



Organisms that Survive for Long Periods 



Only a few disease-producing microorganisms are able to survive in 

 the soil for any considerable periods of time. These few include the or- 

 ganisms causing tetanus, gas gangrene, anthrax, certain skin infections, 



