CLOSTRIDIUM PASTORIANUM 171 



mately become of service in the nutrition of ordinary 

 green plants through the processes of decay and nitri- 

 faction. The species of Azotobacter add considerable 

 quantities of combined nitrogen also, and a small increase 

 is due to organisms belonging to the genus Clostridium. 



It is not too much to say that the practical application 

 of the forces possessed by these and similar organisms is 

 a matter of the utmost importance for the production of 

 crops of all kinds, and a complete determination of the 

 conditions under which they carry on their functions to 

 the greatest advantage, is certain to lead to far-reaching 

 effects upon the world's agriculture. 



i. Clostridium pastorianum, Win. In 1895 Wino- 

 gradsky isolated from the soil of St Petersburg an 

 organism which was capable of assimilating free nitrogen 

 when grown under anaerobic conditions in a medium con- 

 taining dextrose and certain inorganic compounds. A 

 solution containing 40 grams of dextrose was inoculated 

 with a pure culture of the bacillus, and a stream of pure 

 nitrogen was kept passing through it. After twenty 

 days the sugar had disappeared, and analysis showed an 

 increase of 53.6 milligrams of nitrogen in a combined 

 form in the solution. The dextrose was decomposed, 

 42 to 45 per cent, of it appearing as butyric and acetic 

 acids, the rest being split up with the formation of carbon 

 dioxide and hydrogen. Usually small traces of isobutyl 

 or propyl alcohol and lactic acid are found also. 



Winogradsky named the organism Clostridium pas- 

 torianum. It is a strict anaerobic bacillus, and can 

 assimilate nitrogen in media free from nitrogenous com- 

 pounds when oxygen is eliminated. It can also fix free 

 nitrogen in solutions even when air is admitted if aerobic 

 species are present to remove the free oxygen and create 



