FERMENTATIVE CHANGES. 123 



have been shown to have the power of bringing about 

 this change. 



(e) Sulphuretted hydrogen fermentation. A large number of 



different bacteria have been shown to have the power, 

 under certain conditions which are not exactly known, 

 of producing sulphuretted hydrogen by their action 

 upon albumen. 



(f) Cellulose fermentation. Cellulose, which forms the larger 



portion of the tissues of straw and other vegetable 

 matter, is, under the influences of an organism known 

 as Bacillus amylobacter and other bacteria, converted 

 eventually into carbon dioxide, CO 2 , and methane, CH 4 , 

 though many intermediate products, e.g., acetic acid, 

 CH 8 .COOH, free hydrogen, and perhaps butyric acid, 

 C 8 H 7 .COOH, have been detected. 



The process is anaerobic and the bacteria producing 

 it have been detected in the intestines of cattle. 



(g) Other carbohydrates, chiefly starch, various sugars, and 



gums, occur in dung and readily undergo change by 

 the influence of many bacteria, some aerobic, some 

 anaerobic. 



Carbon dioxide, water, lactic acid, CH 3 .CH.OH. 

 COOH, butyric acid, CH 8 .CH 2 .CH 2 .COOH, and some- 

 times free hydrogen are formed. 



A study of the gases evolved during fermentation of manure 

 was made by Schloesing in 1892." He found that in presence 

 of air the temperature of a manure heap is raised by the action 

 of aerobic organisms until purely chemical oxidation sets in 

 and may go on until the temperature is so high that destruc- 

 tion of the organisms is effected. No combustible gases are 

 produced. By allowing the fermentation to proceed in a 

 current of nitrogen or other indifferent gas the anaerobic 

 bacteria only are active and carbon dioxide and marsh gas are 

 chiefly produced. 



The details of one experiment may be of interest. 124-4 

 grammes of fresh manure were allowed to ferment in an 

 atmosphere of carbon dioxide for two months ; in this period 

 nearly 9 litres of gas were evolved, the maximum rate of 



* " Annales Agronomiques," 18, 5; J.C.S., 1892, abst. 1123. 



