724 



CONTRIBUTIONS TO OUR KNOWLEDGE OF SOIL 

 FERTILITY. 



No. xiv. The Stimulative Action of Chloroform retained by 



THE Soil. 



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



Society. 



It appears to be a general rule, that substances which act as 

 protoplasmic poisons also behave as stimulants in minute doses. 

 This is the case with animals and man, with higher plants, and 

 even with single cells such as bacteria. Fred (Centrlb. f. Bakt. 

 2te Abt. xxxi., 185) showed that bacteria growing in dilute 

 bouillon were favourably influenced by the presence of poisonous 

 chemicals such as copper sulphate, ether, carbon bisulphide, 

 potassium bichromate or salvarsan, when in dilutions of from 

 1-100,000 to 1-1,000,000, according to the kind of microbe. 



When a soil is treated with a volatile poison, such as chloro- 

 form, and then exposed to the air, the disinfectant is soon dis- 

 sipated. The effect of the temporary action of the chloroform is 

 shown in an alteration of the soil-constituents, whereby the 

 fertility is increased. Several reasons have been suggested for 

 the change, all depending upon the action of the volatile disin- 

 fectant. Some groups of bacteria are destroyed wholly or in 

 part, while others persist, and, under suitable conditions of 

 moisture and temperature, multiply with considerable rapidity. 

 The ammonia-producers are included among the persistent forms. 

 But the soil is altered in some way, for it is able to support a 

 greater bacterial population than formerly. 



The hypotheses, that have been advanced to explain the altera- 

 tion, include that of Russell and the Rothamsted school, who 

 believe that it is brought about by the destruction of the pro- 

 tozoa which normally prey upon the bacteria. Unfortunately for 

 the hypothesis, the addition of the so-called pure cultures of pro- 



