70 PHYSIOLOGY OF NUTRITION. 



e.g. in the soil, into Nitric acid. 5 This nitrification is effected by 

 a Schizomycete known as Nitromonas,* and there is perhaps no 

 soil which is completely free from it. 



We fill a flask with 100 c.c. of a culture fluid containing to 

 every 100 c.c. of water 0"05 gr. (NH 4 ) 2 S0 4 , O'l gr. KH 2 P0 4 , 

 and 1 gr. Mg C0 3 . To the solution we add a little soil from 

 arable land, so as to infect it with Nitromonas. After about a 

 month, it can be proved by the diphenylamine reaction that a 

 large quantity of Nitric acid has been formed in the fluid. The 

 solution remains clear. A thin skin forms on the surface of 

 it, and in the sediment of Magnesium carbonate are produced 

 zooghjea forms of bacteria, through the mucilaginous nature of 

 which the particles of carbonate are irregularly glued together. 

 I observed this particularly well in a culture which had stood for 

 three months. 



A number of flasks are now provided with culture fluid as 

 above. The flasks are closed with plugs of cotton wool, and the 

 solutions are sterilised by boiling. After boiling for a long time 

 we let the solutions cool, shake up the previously prepared 

 Nitromonas culture, and infect each of them with a drop of it. 

 One flask is left standing in the air ; another is exposed to air 

 free from Carbon dioxide, being placed in the apparatus described 

 and figured in 16. After some time, e.g. a month, it is found that- 

 vigorous nitrification by the developing Nitromonas is only ex- 

 hibited in the culture fluid to which atmospheric Carbon dioxide 

 has had access. The Carbon dioxide of Magnesium carbonate 

 cannot be worked up by this fungus. If culture fluid contained 

 in a flask provided with a plug of cotton wool is sterilised, no 

 formation of Nitric acid takes place in the solution if it has not 

 been infected with Nitromonas germs. In all cases we must, of 

 course, make sure that the culture fluid is free from nitrates at 

 the commencement of the investigations. For this purpose we 

 transfer a drop of the solution to a white dish, and add to it 

 diphenylamine dissolved in Sulphuric acid. 



Nitromonas belongs to a remarkable class of organisms which 

 in the dark, and without chlorophyll, have the power of producing 

 organic substance out of inorganic material. It is very difficult 

 and troublesome to afford a strict proof of this assertion, and 

 therefore we shall not pursue the subject further. It is especially 



* Nitromonas is a bacterium, ellipsoid, and somewhat elongated in form, 

 which does not produce filaments. 



