EDITORIAL. 607 



activity, or rather by the number, of its ammonia -producing bacteria, 

 and the number is kept in equilibrium by the activity of the protozoa 

 for which these bacteria serve as food. Any cause which destroys 

 or reduces the number of the protozoa enables the bacteria to extend 

 their territory, and so raises the fertility of the soil. The authors 

 have also carried out a number of collateral experiments, which 

 show that the direct additions of these large organisms will rapidly 

 reduce the activity of various fermenting media, but this and other 

 positive evidence in favor of the theory have not as yet been 

 published.'' 



The direct evidence furnished by the reports of the investigations 

 of Russell and Hutchinson which have been published to date is 

 hardly sufficient to cause the theory advanced to be fully accepted by 

 scientists, although we are assured that the subject is being rigidly 

 investigated in all of its phases and additional data of great im- 

 portance have already been accumulated. But it is interesting to note 

 that since the publication of the results of this work attention has 

 been called by various writers to certain practices which are thought 

 to bear on the theor3\ 



For example, it has been suggested by Mr. H. H. Mann and others 

 that the beneficial effect of the practice of "rab" on rice lands in 

 India, which consists of turning up the soil and exposing it to 

 the action of the intense heat and light of the sun, may be attributed 

 to partial sterilization, and Mr. J. Aitkin suggests that the beneficial 

 effect of heating the surface soil by means of intense and long-con- 

 tinued fires as practiced in certain parts of England may be at- 

 tributed to the same cause. If further investigation shall show that 

 such practices as these bring about increased productiveness as a 

 result of partial sterilization, it will go far toward demonstrating the 

 practical utility of Russell and Hutchinson's conclusions. 



The practical application of their work is, however, being put to 

 direct test by the investigators themselves, in experiments on methods 

 of increasing the productiveness of soils in the open by the use of 

 various means of suppressing the injurious organisms. Such work 

 suggests a wide field of interesting investigation, not only in con- 

 nection with the handling of garden and greenhouse soils, but also 

 with regard to the effect of intense heat and light upon the bacterial 

 activities of the soils of the arid regions of the United States under 

 various methods v . tiVjge. 



40512— No. 7—10 2 



