196 



A difTereiice in ilie properties of the two microbe-groups appeared 

 from the following reactions: Anaerobes form nitrite from nitrate 

 in a marked degree, indican is split extensively in most cases 

 (oxidation of indoxyl to indigo-blne), a moderate amount of invertase 

 is formed, a large amount of slime (wall-mattei) is formed from 

 saccharose. Aerobes lack these qualities. They liqnefy gelatin, whereas 

 the anaerobes do not. 



My investigation into the propeities of the microbes did not put 

 me in a [position to classify them. 



When examining microbes derived from aerobi^* cultivation for 

 their anaerobic behaviour, it appeared that only B31 grew very 

 well without air, those of B 28 and B 29, however, very badly. 

 The occurrence of these aerobes seems jo show that presumably 

 very small quantities of air are to be found at larger depths in the 

 soil, and that they are carried along with the rainwater that 

 penetrates at a very slow rate into the deeper layers of the earth. If 

 the layer, as is the case here with clay, is only sparingly permeable 

 to water, the dissolved oxygen is allowed to diffuse to the places 

 where it is to be consumed. 



The microbes obtained from anaerobic cultivation developed 

 enormously when living in air. This appeared conclusively when 

 the anaerobic culture-boxes after being opened had been standing 

 for some time exposed to the air. Then the microbe colonies grew 

 larger and larger in a very short time. These bacteria grew very 

 well as aerobes, also on nutrient agar-slants. Tested in this way 

 the majority of the isolated bacteria appeared to belong to the 

 facultative anaerobes, which is consistent with the occurrence of 

 these microbes at greater depths. 



^ 7. Research for some other specific species of microbes. 



We endeavoured to ascertain the occurrence of obligate-aerobic 

 nitrifying bacteria and of Azotobacter chroococcuin, however, with 

 negative result, as could be expected. 



Nor could denitrifying microbes be demonstrated; no more could 

 we detect anaerobic butyric bacteria and anaerobic bacteria which 

 break down cellulose. 



^ 8. Van dim Sleen's Manganese- Theory for the oxidation of 

 organic matter at greater depths in the soil. 



The problem of oxidation of the organic matter in the deeper 

 layers of the earth has been discussed by W. G. N. van dkk Sleen 



