BACTERIAL FERMENTATIONS 



ble air" was being formed continuously and in substantial 

 quantities in all the lakes, ponds, and streams in the vicinity 

 of Como in northern Italy. The initial observation was 

 made in Lake Verbano. Volta found that to detect the 

 gas it was necessary only to disturb the bottom sediments, 

 whereupon a shower of bubbles would rise to the surface. 

 He further recognized a close relation between the abun- 

 dance of combustible gas and the amount of plant material 

 in the sediment, and concluded that the former was derived 

 from the latter. Volta collected samples of the gas from 

 many different sites and determined the relative proportion 

 of gas and air that would give the most vigorous explosion. 



Chemical knowledge of 1776 did not permit the char- 

 acterization of Volta's inflammable gas. This was first 

 accomplished in 1806 by William Henry, who showed that 

 Volta's gas was apparently identical with the main constitu- 

 ent of synthetic illuminating gas, which was later called 

 methane. 



During the next sixty years several eminent scientists, 

 including Bunsen and Boussingault, became interested in 

 methane formation. Their work, which consisted mainly of 

 collecting and analyzing gas samples from various sources, 

 served to corroborate Volta's conclusion that methane is 

 formed abundantly in nature and is generally associated 

 with the decay of plant materials covered with water, but 

 no new concepts were developed. 



The first definite indication that methane is formed by a 

 microbiological process was obtained in 1868 by Bechamp, 2 

 a student of Pasteur. Bechamp had previously studied the 

 decomposition of sugar and starch that occurred when these 

 substances were added to a simple inorganic medium con- 

 taining chalk and incubated in the absence of oxygen. He 

 ascribed the resulting fermentation to a living "ferment" 

 which he thought was originally present in the chalk and 



