166 



JAMES M. SHEEMAN 



with pots each containing one kilogram of soil. The number 

 of protozoa was determined by the dilution method, while the 

 types were determined by the inoculation of 25 grams of soil 

 into sterile hay infusion. 



The effect of volatile antiseptics upon the active protozoa 

 was determined by the treatment of soils with carbon bisulphide 

 and toluene and by determining the number of protozoa one 

 day after treatment and again after two months. The results 

 (Table XXVI) show that the active protozoa are not exter- 

 minated and again multiply to numbers equivalent to those 

 found in normal soils. Monas sp., Dimorpha radiata and Flagel- 

 late A were all observed on the 1/10,000 dilutions after two 

 months. 



TABLE XXVI 

 Effect of toluene and CS2 on the soil protozoa 



In another experiment toluene, carbon bisulphide and chloro- 

 form were used, and samples were taken at the end of one month 

 to determine the number and types of protozoa present. In 

 this test it was found that the protozoan fauna had not been 

 simplified, as far as could be noted by microscopic examination, 

 there being present a very complex mixture of ciliates, flagellates 

 and amoebae. At the end of a month the active protozoa were 

 again present in just as large numbers as are found in untreated 

 soils. 



In the foregoing tests the antiseptics used were left in the 

 soil. It was also thought desirable to treat some soils by the 

 method followed by Russell and Hutchinson. These workers 

 usually employed 1 per cent toluene and then after one day 

 spread the soil out to allow the antiseptic to evaporate. Four 

 pots of soil were treated after this manner and four other pots 



