BY R. GREIG-SMITH. 



•243 



having destroyed some of the toxin. The gradual leveUing up 

 of the numbers in the untreated and lieated soils, as time went on, 

 favours this view. The slow diminution of the bacteria in the 

 heated soil cannot be explained otherwise than by the autointoxi- 

 cation of the growing bacteria. The chloroform-treatment lias 

 clearly produced a profound change in the soil, and in the absence 

 of protozoa, this must be ascribed to the redistribution of the 

 fatty matters of the soil, whereby the nutrients are made more 

 available.* 



It is evident that the action of the volatile disinfectants upon 

 the sewage-sick soils is not, as Russell and Golding athrm, to 

 destroy the phagocytic protozoa, so much as to bring about a 

 segregation of the agricere in which such soils ai'e specially rich- 

 The amount of the gum and fatty material in these soils is enough 

 to justify the old idea that the sickness is due entirely to the 

 physical state whereby the easy percolation of water or sewage 

 and of air are prohibited. Inferentially the protozoa, etc., have 

 a very limited action, if any, in causing or assisting sewage- 

 sickness in soils. 



* The toxins are also made more available, and it becomes a question of 

 tlie qaantit3- of luitrieuts and of toxins liberated, as well as of the suscep- 

 tibility of the bacteria to the toxins. 



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