'62 R. GREIG-SMITH. 



toxic. If they are nutritive, traces of chloroform enhance 

 the nutritive effect, while, if the extracts are toxic, they 

 increase the toxicity. 1 Chloroform therefore acts in a 

 manner similar to the soil toxins, or to reverse the point of 

 view and to generalise, the toxins behave like the volatile 

 disinfectants so far as their stimulating and toxic powers 

 are concerned. This is what we should expect, for, toxins 

 are really poisons and should behave like the disinfectants, 

 and the mineral poisons such as arsenious oxide, copper 

 sulphate and the like. It follows that the bacterio-toxins 

 are the natural soil stimulants, and if kept under control, 

 so that the amount never becomes excessive, they will 

 conduce to increase the soil fertility. 



The Action of Lime. 



The action of quicklime upon the bacteria of the soil 

 appears to have been first investigated by H. Fischer, 2 who 

 found that it acted much as a volatile disinfectant, in first 

 depressing then augmenting the bacterial numbers. With 

 0*7%, the bacteria rose in 16 weeks to 420 millions per gram. 



Hutchinson 3 showed that the action of caustic lime was 

 intermediate between that of the volatile disinfectants and 

 that of a high temperature. Many bacteria are killed, the 

 larger protozoa are destroyed and there is a decomposition 

 of organic matter. 4 The bacteria remain depressed until 

 the excess of calcium oxide is converted to carbonate when 

 there is an active bacterial multiplication. In a later 

 paper, in conjunction with MacLennan, 5 he showed that 



1 Proc. Linn. Soc. New South Wales, 1915, 724. 



2 Cent. Bakt., 2te, 26, 263. 3 Journ. Agr. Sci., 5, 320. 



* It is claimed that the decomposed organic matter exercises a "feed- 

 ing effect" by which is meant that the bacteria quickly rise to enormous 

 numbers, but these are not sustained. This is generally noted with soils 

 that have been sterilised by heat and sometimes by disinfectants. It is 

 open to question whether it is due to an increased amount of available 

 nutriment or to the destruction of toxins or to a combination of the two. 



5 Ibid., 6, 302. 



