DECOMPOSITION OF ORGANIC MATTER IN THE SOIL 377 



fermentation products falls within the limit of error. These experi- 

 ments show that about one-half of the fermentation products is 

 gaseous and that the other half consists of acetic and butyric acids. 



McBeth has shown that the cellulose-dissolving bacteria are unable 

 to produce gaseous products in cellulose or sugar solutions in which 

 they make a luxuriant growth. The compounds formed, under natural 

 conditions, by the cellulose dissolving bacteria are used by other micro- 

 organisms and split into simpler products. The carbon dioxide formed 

 is presumably due in all cases to secondary fermentations. The 

 organic acids noted by early investigators were, for the most part at 

 least, presumably due to secondary fermentations and not to the action 

 of the cellulose-dissolving forms. 



The Oxidation of Methane, Hydrogen and Carbon Monoxids. Aside 

 from cellulose, methane may also be produced from various other carbo- 

 hydrates, organic acids and proteins. Large amounts of methane are 

 thus contributed to the atmosphere by swamps, manure heaps and low- 

 lying meadows. In a purely chemical way methane may also be set 

 free from volcanoes and mineral springs. The constant additions of 

 methane, ethane, hydrogen and carbon monoxide represent a consid- 

 erable amount of potential energy. It is important to know, therefore, 

 whether these materials are at all utilized. 



That methane may be utilized by bacteria as a source of energy was 

 first shown by Sohngen in 1905. He isolated an organism named by 

 him B. methanicus that showed itself capable of growing in inorganic 

 solutions confined over an atmosphere of methane, oxygen and nitrogen. 

 The methane gradually disappeared and there were formed considerable 

 quantities of organic matter. The ability to oxidize methane has been 

 claimed for a number of other organisms by Sohngen and others. 



Early observations on the ability of moist soil to cause the oxidation 

 of hydrogen are credited to de Saussure (1838). Many years later 

 (1892) Immendorff called attention to the same fact. It was not, 

 however, until 1905 that the oxidation of hydrogen was shown to be a 

 specific biological process. In that year papers by Sohngen and Kaserer 

 reported experiments wherein inorganic solutions confined under an 

 atmosphere of hydrogen, oxygen and carbon dioxide and inoculated with 

 very small quantities of soil developed a bacterial membrane at the 

 surface. The hydrogen was oxidized and organic matter produced at 

 the expense of the energy set free. The observations just noted have 



