BY K. GREIG-SMITH. 6S7 



and two parts of tap- water (33 %). There is, however, no 

 evidence of any stimulating influence of the volatile disin- 

 fectant. 



The Search for an Antitoxin. — The knowledge of the exist- 

 ence of a toxin in the soil naturally leads to the desire to find 

 an antitoxin or substance which, when applied after the 

 manner of a fertiliser, will favour the growth of bacteria by 

 neutralising the toxin. Practically this must be cheap, and 

 easy of application. So far as economy is concerned, we have 

 seen tliat exposure to the sun's rays diminishes the toxicity, 

 and doubtless the benefits that accrue from working the soil 

 are, in part, traceable to this fact. It is possible that this, 

 together with the natural decay, is the only economic method 

 of combating the accumulation of the toxic products of 

 bacteria. 



But an enhanced fertility has been obtained, in certain 

 cases, by the use of substances which are not generally con- 

 sidered as fertilisers, inasmuch as they do not contain the 

 customary nitrogen, phosphoric acid, potash or other con- 

 stituent taken up by the plant in quantity. For example, 

 ferrous sulphate and manganese sulphate have been used as 

 manures, in some cases with advantage to the crop; copper 

 salts also, when used as fungicides, have generally a distinct 

 action in increasing the growth of plants. It is possible that 

 these may act indirectly as toxin-destroyers. 



To ascertain the action of saline substances as antitoxins, 

 two methods might be employed in the laboratory. They 

 might be added to the soil itself, or to an extract. In the 

 latter case, the antitoxic action would probably be more pro- 

 nounced, for the reason that the toxic action is more promi- 

 nent. Both methods were tried, and the substances that 

 were tested were copper sulphate, copper sulphate followed 

 by lime-water, manganese siilphate, ferrous sulphate, ferric 

 chloride, sodium phosphate, ferrous sulphate and lime-water 

 with air blown through until all the iron had been oxidised, 

 aluminium sulphate, superphosphate, sodium sulphite, sul- 



