THM NITEOGEN CYCLE 



473 



to bacteria, and also certain of the less resistant bacteria, 

 thus permitting the more resistant species to multiply 

 very rapidly owing to the absence of the bacteriotoxins. 



In order to ascertain whether chloroform has any effect 

 other than the destruction of protozoa, Greig-Smith 

 applied it to soil previously heated to 62° C. (which he 

 had found was sufBcient to kill all protozoa), and then 

 determined the number of bacteria in untreated soil, in 

 heated soil, and in soil heated and treated with chloro- 

 form. The counts to a gram of soil were made at inter- 

 vals, and are shown below : ^ — 





At 



Staet 



52 



4 Days 



12 Days 



25 Days 



39 Days 



Untreated soil 



680,000 



2,700,000 



4,300,000 



5,400,000 



Soil heated 













at 62° C. 



16 



15,800,000 



11,800,000 



9,000,000 



8,000,000 



Soil heated 













at 62° C. 













and treated 













with chlo- 













roform 



13 



24,600,000 



45,400,000 



41,600,000 



90,000,000 



Greig-Smith concludes that as the bacteria developed 

 more rapidly in the soil treated with chloroform after 

 heating than in the soil which w^as only heated and in 

 which the protozoa were presumably dead, the chloro- 

 form must have exerted some beneficial effect other than 

 the destruction of protozoa, and assumes that this is due 

 to the removal of " agricere." 

 Partial or complete sterilization of soils has been pr^c- 



1 Greig-Smith, R. Contributions to our Knowledge of Soil 

 Fertility. Proc. Linnaean Soe. New South Wales, 1912, Part II, 

 pp. 23^-243. 



