230 FARMYARD MANURE 



chalk, and a small quantity of fresh horse dung or river 

 mud was added. The cultures were kept at 35 C. for 

 some months, and the gases evolved were collected at 

 short intervals over mercury and analyzed. When 

 fermentation was complete about 2 grams of filter paper 

 were found to have yielded 552 c.c. of mixed gases, 191 

 c.c. being methane, and 361 c.c. carbon dioxide. At 

 the same time, acetic and butyric acids were produced in 

 the proportion of 9 molecules of the former to I of the 

 latter. The bacteria giving rise to 

 this type of fermentation were 

 found to be anaerobic, rod-shaped 

 bacilli, slightly bent and about 5 //- 

 long and .4 /* thick. They form 

 spores i n in diameter at the ends 

 of the cells, the latter then re- 

 sembling miniature drumsticks 

 (Fie S7). 



FIG. 37. Organism which gives v 5 " -" ' 



rise to methane fermentation of Omeliattsky dlSCOVCred alsO 



cellulose (X 750). ... 



that in river mud and fresh 



horse dung another very closely allied organism was 

 present, which in pure cultures ferments cellulose with 

 the production of carbon dioxide and hydrogen, no 

 'methane being formed. Under the action of this 

 bacterium about 3.5 grams of cellulose gave 810 c.c. of 

 gas, 154.3 c - c - f which were hydrogen and the rest 

 carbon dioxide. Acetic and butyric acids were produced 

 as in the methane fermentation but in a different propor- 

 tion, there being 1.7 molecules of the former to I of 

 the latter. The organism responsible for the hydrogen 

 fermentation of cellulose is similar in form, but some- 

 what larger than that which gives rise to methane, being 

 4 to 8 /a (or sometimes 10 to 15) long, and .5 n thick; 



