CHAPTER VIII 
GENERAL REFLECTIONS AND CON SIDERATIONS 
ON DISEASE TREATMENT 
Soil and Water Sterilization 
THE practice of soil sterilization is now an accepted 
method of increasing the fertility of infertile soils and of 
ridding them of diseases and pests. 
When soils are heated, they undergo a process of change, 
the extent and form of which varies with the increase of 
temperature and length of time it is operative. Even 
slight increases of temperature are important as affecting 
the functions of roots and the behaviour of soil organisms 
as well as the chemical reactions occurring in the soil. 
When, however, soils are heated until the temperature 
becomes approximately 97° C. (207° F.) important 
changes take place and the soil becomes “ partially 
sterilized.” Partial sterilization has a beneficial effect 
upon soils, which is most marked in infertile or “ sick” 
soils. Complex chemical compounds, unavailable as 
plant foods, are split up by the heat, and the simple com- 
pounds thus set free are either directly available as plant 
foods or rendered so in a short time by the bacteria 
present in the soil. The high temperature affects the 
living organisms of the soil in a differential manner, 
those which possess thin walls and are not specially 
adapted to resist abnormal conditions being killed, while 
others survive in virtue of possessing resistant spores and 
other reproductive bodies. Thus the non-sporing bacteria 
are destroyed, while those possessing spores which are 
resistant to abnormal temperature conditions are able 
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