THE NITROGEN 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, Gr'eig-Smith 

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

 had found was sufficient 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 : 1 — 



Greig-Smith concludes that as the bacteria developed 

 more rapidly in the soil treated with chloroform after 

 heating than in the soil which was 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 prac- 



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

 Fertility. Proe. Linnsean Soc. New South Wales, 1912, Part II, 

 pp. 238-243. 



