DISTRIBUTION AND HABITAT OF THE BACTERIA. 695 



were able to show that the formation of carbonic acid in Production of 



nitric acid and 



the soil was entirely the result of the life of lower organ- carbonic acid, 

 isms. Further, Gayon and Dupetit, as well as Deherain 

 and Maquenne, have furnished proof that when oxygen is 

 deficient a reduction of the nitrates to nitrites, ammonia 

 and nitrogen can be brought about by the bacteria 

 of the soil. According to investigations made by Reducing 

 Heraeus (Zeitschriftf. Hyg., vol. L), many forms of bac- 

 teria (such as bac. prodigiosus, cheese spirilla, Finkler's 

 spirilla, typhoid bacilli, anthrax bacilli, staphylococci) 

 are able to oxidise ammonia to nitric acid ; while other 

 species (for example, two kinds of bacilli cultivated from 

 water) cause the reduction of the nitrates in a marked 

 manner. Schlosing and Miintz held that nitrification was Nitrification 



, , , , , -1.1 1S n t caused 



caused exclusively by one species of bacteria which was exclusively by 

 isolated by them from the soil ; but their description of the ]* ^ teria of 

 bacteria does not at all indicate that they worked with a 

 really pure cultivation, and the investigations of Heraeus 

 compel us to adopt the view that a large number of 

 bacteria are capable of causing nitrification either by 

 simple assimilation and oxidation, or by a sort of fer- 

 mentation. In soil the conditions are especially favour- J ut the most 



favourable 



able for some of these bacteria which act by oxidation conditions for 

 because concentrated solutions and large quantities of are^rese^tod 

 organic material further the multiplication of the re- bv the soil - 

 ducing bacteria, while in more dilute nutrient substrata, 

 which is usually the condition even of unclean soil, the 

 oxidising bacteria gain the upper hand. Hence in by far the 

 greatest number of cases we observe oxidation processes 

 in the soil, which on account of the marked subdivision 

 of the material in thin layers, the intimate contact of 

 air, and the simultaneous surface attraction of the soil, 

 lead to an extremely rapid and complete destruction of 

 organic material. As to the individual phases of the 

 decomposition of the soil, and as to the various influences 

 which act on it, we must await the results of continued 

 investigation with pure cultivations of bacteria from the 

 soil under various conditions. 



We also possess some observations, although on the Transport of 

 whole unsatisfactory ones, as to the distribution and 



