166 CONTRIBUTIONS TO OUR KNOWLEDGE OF SOlL-FERTILITY, XV. 



organisms liave little or no action in bringing about a pro- 

 nounced limiting effect upon the numbers of bacteria in the soil. 

 The untreated soil had recovered from its air-drying by the 78th 

 day, and had become normal: while the toluened and heated 

 soils had not arrived at this condition by the close of the experi- 

 ment on the 317th day. From a general glance at the numbers, 

 we see that, in the heated soil, the numbers rapidly rise to a 

 maximum and then fall; while, in the toluened soil, the numbers 

 slowly rise, and the height of the curve is maintained for a 

 longer time. I have already suggested that the effect of toluen- 

 ing appears to be to liberate nutrients, while heat seems to 

 destroy toxins; but this is only a suggestion, for there is un- 

 doubtedly some other factor which is more potent. Possibly 

 this is the alteration of the flora, which masks anything but a 

 general difference between the results of the two methods of 

 treatment. 



The small experiment with acetone was introduced to test the 

 contention of Buddin,* who said that it did not act as a volatile 

 disinfectant, that is, it did not produce any partial sterilisation- 

 effect, until 5-8% by weight had been added to the soil. From 

 his experiment with acetone, which is a fat-solvent, he concluded 

 that the volatile disinfectants do not influence the soil by reason 

 of their power of dissolving the fatty matter (agricere) and 

 facilitating .the solution of the soil-constituents, as was suggested 

 by me. Small as my experiment is, it shows that Buddin's asser- 

 tion is too sweeping, for the action of acetone is one of degree, 

 its action being much the same, though more feeble than toluene 

 The addition of 5% (by volume = 4% by weight) to the soil 

 brought about an effect similar to that of 2% of toluene, and 2% 

 of acetone had a less pronounced action. The high count on the 

 second day, with the smaller amount, is peculiar and points to 

 a stimulating effect. With regard to the fat-dissolving action 

 of the volatile disinfectants, I have already said that the action 

 is only one of many, and that it plays a part, though probably 

 a small one, in the greater question of soil-fertility. 



"" Journ. Ag. Sci., vi., 418. 



