358 EXPERIMENT STATION RECORD. 



a soil sterilized at 1-0° is iuociilated with a soil which has not beeu 

 heated, the nitrifying organisms renew their activity and nitrates 

 reappear. 



When we remember that the nitrogenous matter of the soil is inert, 

 and that generally it exercises no i)erceptible efl'eet on vegetation, and 

 if we recall, on tlie contrary, that nitrates i)ossess such etticacy that the 

 yield obtained in a sterile soil increases in proportiou to the weight of 

 nitrate added, we can understand the importance of the discovery of 

 Schlosing and ^liintz and the new ideas which it suggests to agricul- 

 turists, for to the latter henceforth a fertile soil is to be h)oked upon as 

 essentially a culture medium for nitric ferments. 



The existence of ferments deduced from the preceding observations 

 was known a dozen years before an attempt was made to isolate the 

 specific organisms. These were first studied by an eminent Kussian 

 phyvsiologist, Winogradsky. After numerous experiments, manifesting 

 great skill and patience, Winogradsky succeeded m isolating the 

 nitrous ferment, /. e.^ the living organism which carries forward the 

 oxidation of ammonia 1°. Five or six days after inoculating a liquid 

 which contaiiuid per liter I gm. of suli)hate of ammonia, 1 gm. of phos- 

 phate of potash, and a little carbonate of magnesia without any organic 

 matter, Winogradsky observed a slight cloudiness in the solution, due 

 to somewhat fusiform oval organisms, moving in the hquid with great 

 activity. This activity, however, was not of long duration, for after a 

 short time the organisms dropi)ed to the bottom of the liquid and cov- 

 ered the carbonate of magnesia with a slimy secretion. 



It is interesting to observe that Winogradsky succeeded in growing 

 the nitromouas in a medium free from organic matter and containing no 

 carbon except that of the carbonic acid of the carbonate of magnesia. 

 In order that the microorganisms might utilize this carbon in the for- 

 mation of their tissues the carbonic acid was first set free and then the 

 carbon separated from the oxygen, without the intervention of any 

 exterior energy. This was accomplished by the heat generated by the 

 combustion of the hydrogen of ammonia. 



Winogradsky observed further that the transformation of anmionia 

 into nitric acid was accomplished in two successive stages. The nitro- 

 mouas described above gave only nitrous acid. Tlie complete oxida- 

 tion of nitrogen was due to another organism entirely different from 

 the nitromouas. The organism which transforms the nitrous acid to 

 nitric acid is a small irregular angular rod, which exercises the specml 

 function of superoxidation but is entirely incapable of oxidizing 

 ammonia. This is a portion of the work of the highest interest.' 

 When nitrates appear in a culture medium the medium contains two 

 different microorganisms — the nitromouas, which transforms ammonia 

 into nitrous acid, and the small rods, which transform nitrous acid 

 into nitric acid. 



' Ann. Inst. Pastonr, 4 (1890), pp. 213, 257, 7(50; 5 (1891), pp. 92, 577 (E- S. R., 2, p. 751 j 

 3, p. 551) ; also Compt, Rcud., 113 \mdl), pp. 89-92 (E. S. R., 3, p, 550). 



