BY U. GREIG-SMITH. 



815 



heating at 94° has completely destroyed the toxin which remained 

 in tlte extract. 



The Relative Variation of the Toxix in Soils. 

 Experiment v. 



Soil 1 extract 



Soil 1 extract heated 



Soil 4 extract 



Soil 4 extract heated 

 Control (no soil) 



1,000 bacteria became 







36,500 







2,000 



117.200 



The soils were extracted shortly after their arrival in the 

 laboratory, 0"2 % NaCl having been used for their extraction. 



The experiment is interesting from the fact that the fertility 

 •of these two soils was widely different. No. 1 was described as a 

 " fairly rich alluvial soil," with a fertility of 8 points (10 being 

 the maximum obtainable). No. 4 was a poor sandy soil, with a 

 fertility of 2. Tlie poorer soil had the larger amount of toxin. 

 Both extracts were made in precisely the same way, and at the 

 same time (with an interval of half-an-hour between them); and, 

 as they were heated at the same time and for the same time in 

 test-tubes, in the same boiling water, the numbers can be taken 

 as being relative, one to the other. 



To show that the lessened growth in the heated extract of 

 Soil 4 was due to partially destroyed toxin, and not to the 

 absence of nutritive matter, the unheated extract was boiled, 

 two days afterwards, and tested. 



