54 



maxiniuni increase in numbers of microorganisms in 

 the ciimarin, vanillin, and quinoline treated soils the 

 Actinomyces have practically disappeared, reappear- 

 ing later with the decrease in numbers as is shown for 

 cumarin in Table II, and as was observed for quinoline 

 and vanillin at a date later than August 30. The sig- 

 nificance and cause of this is not clear. 



Discussion. The increase in numbers of microorgan- 

 isms observed in the treated pots appears to be much 

 similar to that found in "partial sterilization" with 

 steam, carbon disulfide, toluol, etc., by Hiltner, Russel 

 and Hutchinson and others. They have found in gen- 

 eral that treatment of the soil by sterilizing agents, in 

 quantity or degree insufficient to cause complete ster- 

 ility, frequently produces an enormous temporary in- 

 crease in the microscopic flora of the soil. The increase 

 is often preceded by a depression. Buddin (1) has 

 studied the effects of pyridine. He found a marked 

 effect, obtaining a maximum number of 3,500 millions 

 of organisms in the pyridine treated pots when the 

 check gave but 13 millions. 



The explanations offered for this phenomenon have 

 been various. Russell and Hutchinson (18) have stated 

 that the increase in the number of bacteria is due to 

 the fact that the antiseptic destroys the bacteria con- 

 suming protozoa. Other explanations offered by va- 

 rious investigators are summarized by Lipman (12) as 

 "(1) increase in availiable food for bacteria; (2) ren- 

 dering soil toxins insoluble; (3) destroying bacterio- 

 toxins; (4) acceleration of biological processes." Bud- 

 din (1) suggests for pyridine that pyridine affords a 

 magnificient diet for bacteria, and provides the simple 

 case of two or three species feeding directly on the 

 substance itself or its decomposition products. David- 

 son (3) observed a growth of molds and fungi in a 

 solution containing 200 parts per million of cumarin 

 which had stood for some time and suggests that micro- 

 organisms may destroy cumarin and vanillin in the 

 soil. (Funchess (8, 17) has found that pyridine and 

 quinoline are apparently nitrified in the soil. These 

 facts and suggestions, as well as others not mentioned, 

 appeared to indicate that Buddin's explanation might 

 also hold for vanillin, cumarin and quinoline. In order 

 to determine whether microorganisms acted on these 

 compounds in the soil, the following method was used: 



