BY R. GREIG-SMITH. 



187 



grams of garden-soil and 300 c.c. of distilled water. The two 

 were shaken 300 times during an hour, and filtered. The re- 

 action to methyl-orange was -0-14, although a paste of the soil 

 was acid to litmus. 



A similar extract, made on December 6th, had a reaction to 

 methyl-orange of - 0-24. This extract was examined, with the 

 following results. 



Quantities of lactic acid and of carbonate of soda were added 

 to vary the reaction, and the treated extracts were seeded with 

 the test-organism in the usual manner. The following numbers 

 were obtained after the usual 20 hours' incubation at 22". 



Experiment xxxi. 



The true neutral point was reached by adding 006° of acid, 

 that is to say, the methyl-orange indication was - 0-19 in excess. 



The effect of shaking up various quantities of soil and water 

 was tested, to see the differences in the reaction of the extracts. 

 Round numbers were taken, but, as the solid contained 8% of 

 moisture, a correction was made. 



