RV K. GKKIG-.SMITll. 



G89 



EXPERIMKNT X. 



20 gr. soil + 1 c.c. suspension + 1 c.c. Thiosulphale, %, 

 thiusulphate or water. I in water added. 



Hawkesbiiry soil No. 4 



Sand 



1,000 bacteria 

 became 



3,100 

 2,800 

 2,950 

 4,750 

 5,500 

 5,450 

 130,000 

 540,000 



Although the results obtained with the extracts (Experi- 

 ments vii. and viii.), especially of the Hawkesbury soil, raised 

 the hope that some neutralisation of the toxin had occurred, 

 yet the findings with the soils themselves (Experiments ix. 

 and X.) indicate that the bacterial increase was, in all pro- 

 bability, caused by the stimulation of the salt. The toxin is 

 probably unaffected. 



The Action of Heat and of Fat-Solvent upon Soils. — In 

 endeavouring to demonstrate the action of fat-solvents in 

 removing the agricere from soils, it is necessary to eliminate 

 any disturbance produced by the bacteriotoxins and by pro- 

 tozoa.* This would appear to be a simple matter, since both 

 of these are destroyed by heat. Unfortunately, as the natural 

 toxins are destroyed, the heat-toxins of Pickering are 

 developed, and a soil which has been heated for some time, 

 becomes exceedingly toxic. This will appear evident from 

 the consideration of the following experiments. In the tables, 

 I have calculated the increase from 10 original cells of Bac. 

 2)rodigiosus, the micro-organism used in the experiments, 



* When a soil has been air-dried and stored in that condition for any 

 length of time, it is exceedingly probable that the phagocytic protozoa will 

 have been destroyed, or so weakened that they will be unable to become 

 suflBoiently active to exercise their phagocytic functions within the time, 

 viz. , 20 hours, occupied in the experiments. But on account of the un- 

 certainty of their being really inactive, means had to be adopted to ensure 

 their inertness. 



