679 



CONTRIBUTIONS TO OUR KNOWLEDGE OF SOIL- 

 FERTILITY. 



iv.The Agricere and Bacteriotoxins of Soil. 



By R, Greig-Smith, D.Sc, Macleay Bacteriologist to the 



Society. 



In the first paper of this series, I showed that, in opposition 

 to Russell and Hutchinson, there were in soils certain toxins 

 which restrained the growth of the soil-bacteria. These were 

 partly or entirely destroyed by heat, by sunlight, and by 

 storage, especially in aqueous solution. Furthermore, I 

 showed that soil contained a fatty or waxy substance, agri- 

 cere, which was dissolved and carried to the surface of the 

 soil by certain fat-solvents. These solvents are also disinfec- 

 tants, and this property of destroying vegetating bacteria is 

 probably responsible for obscuring their other property of dis- 

 solving fatty bodies. 



The research originated in the disbelief of one of the steps 

 which led Russell and Hutchinson to think of protozoa. It 

 was against all bacteriological experience that bacterial toxins 

 should be absent from soil ; and it was only by assuming or 

 claiming that no toxins were in soil, that these investigators 

 were led to believe that phagocytic protozoa were responsible 

 for the limitation of the bacterial content of soils. 



That the soil-protozoa should play a part in checking the 

 multiplication of bacteria in the soil is very feasible, and 

 many of the experiments recorded by Russell and Hutchinson 

 point to their activity. But it does not follow that the pro- 

 tozoa are alone responsible for the limitation in the numbers 

 of bacteria in soil, as Hall* would lead us to believe. Indeed, 

 Russell and Hutchinson are careful to say that they do not 

 wish to imply that the removal of the large organisms is the 

 only cause of the improvement in soils effected by partial 



•Hall, Chem. Soc. Ann. Rep. 1909, 187. 

 60 



