38 JAMES M. SHERMAN 



terial flora of the soil, and likewise upon the higher plants. In 

 support of this stimulation theory some very convincing data 

 have been furnished by Koch (1899) (1911), Nobbe and Richter 

 (1904), Egorov (1908), Fred (1911), Gainey (1912) and others. 



The selective theory of Hiltner and Stormer (1908) holds that 

 volatile antiseptics exert a selective action on the bacterial flora 

 of the soil. It is thought that the soil is so changed that the 

 subsequent development of the beneficial types of bacteria is 

 enhanced, while the harmful forms are suppressed. These in- 

 vestigators believed the increased crop yields obtained to be due 

 to the increase in the amount of plant food elaborated by the 

 beneficial bacteria. 



Bolley (1910) (1913 a) 1913 b) claims that the improvement of 

 soil by partial sterilization is in many cases due to the destruc- 

 tion of certain parasite fungi which attack the plants and thus 

 hinder their growth and development. Another function per- 

 formed by volatile antiseptics according to Grieg-Smith (1911) 

 is the liberation of plant and bacterial food through the solution 

 of the "agricere" or soil wax. 



Other points have been noted in the works of various investi- 

 gators which partially account for the action of certain anti- 

 septics in soil exclusive of their effect upon the protozoan fauna. 

 Buddin (1914) has shown that the treatment of soil with sulphur 

 dioxide increases the number of bacteria very appreciably with- 

 out exterminating the protozoa, while certain other compounds 

 such as pyridine cause an increase in the number of bacteria due 

 to the fact that their decomposition products furnish an excellent 

 source of food for the soil micro-organisms. Hutchinson and 

 MacLennan (1914) have shown that the partial sterilization of 

 soil with caustic lime leads to a chemical breaking down of some 

 of the organic matter of the soil and thus stimulates the subse- 

 quent activities of the bacteria. Fred (1915) in his work on the 

 action of carbon bisulphide in soil has demonstrated that all of 

 this compound does not evaporate when added to the soil, but 

 that some of it remains and is changed to sulphates. 



Some workers believe that the value of partial sterilization by 

 heat is due to the destruction of soil toxins which limit the 



