TRANSFORMATIONS OF CARBON AND NITROGEN. 73 



Omelianski is quite different from this older known species. 

 But this fermentation certainly does occur in practically every 

 place where there is an accumulation of vegetable matter 

 together with sufficient moisture and warmth. It occurs in 

 swamps, in the compost heap and the manure pile. It is also 

 possible that a similar fermentation occurs in the intestines of 

 herbivorous animals. These animals certainly make use of a 

 certain portion of the cellulose material in their foods. From 

 the intestines of such animals have been isolated bacteria which 

 have been found to possess some power of fermenting cellulose, 

 and it has been suggested that it is through their agency that 

 the animals make use of this material. This must certainly be 

 regarded as doubtful since the only facts in our possession are 

 that cellulose is utilized by these animals and that certain cel- 

 lulose-fermenting bacteria have been found in their intestines. 

 But whether this be true or not it is certain that in nature, 

 wherever there is an accumulation of cellulose material, a fer- 

 mentation is set up which returns to the air much of the car- 

 bon in the form of carbonic acid. 



Wood. Another product of plant life somewhat closely re- 

 lated to cellulose is ivoody tissue. The fermentation and de- 

 struction of wood is certainly a matter of necessity if the carbon 

 supply is to be kept constant. That there is such a fermenta- 

 tion is evident to anyone who has walked through a forest and 

 noticed the condition of the fallen trunks and branches. A 

 fallen tree will remain for a time upon the surface of the ground 

 apparently unaltered. But presently it becomes softened by 

 some agency not at first manifest, and the hard, woody mass is 

 slowly but surely converted into a soft friable substance, which 

 is eventually entirely broken into a brownish powder and in- 

 corporated into the soil, contributing to the formation of the 

 humus upon which the fertility of the virgin earth is dependent. 

 This destruction of woody tissue is also brought about by 

 microorganisms, but in this case several different types of fungi 



