94 AGRICULTURAL BACTERIOLOGY. 



universal. The next step in the discoveries was made by 

 Schlossing and Muntz in 1877, when they succeeded in dem- 

 onstrating that this nitrification is associated with the presence 

 of living matter in the soil. This can be easily proved by 

 placing two lots of the same soil under such conditions that, in 

 one, living phenomena may go on, while in the other they are 

 stopped. If, for example, one lot of soil is sterilized by heat- 

 ing it sufficiently to destroy the living germs present, and then 

 this soil is compared with another lot treated in all respects the 

 same except that it is not sterilized, the latter will be found to 

 increase its nitrates while the former shows no such increase. 

 The same results are obtained if the soil is mixed with anti- 

 septics which prevent bacteria growth. In short, anything 

 which prevents the occurrence of life phenomena in the soil 

 prevents the nitrification. 



Such experiments repeated many times and verified by 

 numerous observers soon demonstrated that nitrification is a 

 living process. Inasmuch as such soil contains no plants large 

 enough to be seen, such plants having been entirely removed 

 from the experimental soils, it followed that the living agent of 

 nitrification must be some form of microorganism. It proved, 

 however, to be a very difficult matter to find the organisms 

 concerned in the process. It is true enough that the number 

 of bacteria in the soil is large and that many different species 

 are there found. But although many of these bacteria were 

 isolated and carefully tested, for a long time none proved to 

 have any power of nitrification. Most of them, indeed, pro- 

 duced the reverse effect of deoxidizing nitrates already men- 

 tioned (denitrification), but none of them raised the nitrites 

 into a state of nitric acid. Moreover, none of them could ox- 

 idize ammonia so as to form nitric or even nitrous acid. If a 

 small quantity of soil is added to a solution of nitrite the ni- 

 trite soon becomes converted into nitrate, under the influence 

 of the fermentation started by the presence of the soil. This 



