BY R. GREIG-SMITH. 

 EXPKRIMKNT XXxii. 



189 



The experiment shows that, in the case of a fermented culture- 

 fluid, the lessening of the alkalinity by 0*06° produced neutralitj'. 

 The methyl-orange indication was -0'10°too high. A high 

 indication was also obtained with soil-extiact in Experiment 

 xxxi., and with tap- water in Experiment xxvii. 



The acidity of the extracts of sterilised vegetable-moulds (Ex- 

 periments XV., xvi.) led to an examination being made of the 

 extracts of soil which had been sterilised in the same manner, 

 viz., for two hours at 1 30". 



Two hundred gram-portions were put into sterile bottles with 

 10 c.c. of a suspension of Amoeba Umax, containing 10,660 mobile 

 forms per c c, and 40 c.c. of water. The soil thus had an ex- 

 cessive amount of moisture, 20%; it usually contains from 8 to 

 10%. The bottles were kept at laboratory-temperature, which 

 varied from 18-23°. 



Extracts were made in the usual manner by adding 200 c.c. of 

 distilled water, shaking frequently during an hour, and filtering 

 through porcelain. Uhe extracts were seeded with Bac. pro- 

 digiosus, incubated and counted. 



Experiment xxxiii. 



14 



