BY R. GREIG-SMITH. 



691 



These experiments indicate (and the experimental error 

 being considerable, one cannot consider them other than as 

 an indication) that the action of heat and of chloroform is 

 complex. There is a destruction of a natural toxin and the 

 production of a heat-toxin in both the untreated and treated 

 sets. In the chloroformed sets, the action of the natural toxin 

 is masked by the greater diffusion of the nutrients and of the 

 heat-toxins. The latter apparently diffuse more easily out of 

 the particles of treated than out of the untreated soils. 



Taken as a whole, the experiments show that the fat-solvent 

 has a pronounced action in liberating the nutrients of un- 

 heated soil, and in liberating the toxins of heated soils. The 

 continued action of heat is to destroy the natural toxin, and 

 to produce more and more heat-toxin. 



The action of carbon bisulphide is different from that of 

 chloroform, inasmuch as the heat-toxin is either not so dif- 

 fusible, or it is largely destroyed. This will be seen from the 

 following. As we have no reason for believing that the heat- 

 toxin can be less diffusible, we may conclude that it is more 

 or less destroyed. There is a doubt, however, about the 

 purity of the carbon bisulphide ; some samples that I obtained 

 were toxic, and it may be that the solvent used in these 

 experiments contained a nutrient. 



Experiment xiv. 



