FERMEKTATION OF CELLULOSE 167 



liquid is removed from the fermentation flask, and so the con- 

 ditions of the experiment are altered as it proceeds. But if 

 the fermentation is mainly confined, as in the case of cellulose, 

 to the deposited matter at the bottom of the flask, the removal 

 of the hquid is not of such serious moment, and it is convenient 

 to have an apparatus the whole of which can be placed in an 

 ordinary incubator. 



Van Iterson found that the decomposition of cellulose in 

 presence of nitrate, as above described, went on at much the 

 same rate as the anaerobic change studied by Omehanskd. He 

 drew attention to the fact that the nitrite produced is readily 

 re-oxidised by the organisms of nitrification, and consequently 

 that in presence of air the nitrate is being continually repro- 

 duced, and the conditions for the destruction of cellulose are 

 therefore constantly maintained. This observation is of great 

 importance in connection with the destruction of cellulose in 

 the bacterial filter beds employed in the purification of sewage. 



Van Iterson found further that the spores and myceha of 

 higher fungi were also active in breaking down cellulose in 

 presence of air. Thus, if a Uttle leaf mould is placed in contact 

 with moist filter paper in a moist chamber, rotting of the filter 

 paper takes place with production in general of yellow stains. 

 This is probably a complex process wherein various moulds 

 together with chromogenic or pigmenting bacteria take part. 

 It appears that woody fibre resists decomposition under these 

 circumstances, and may remain practically intact for a long 

 period of time in a disintegrated condition, in such end pro- 

 ducts as peat, hgnite, etc. These contain the somewhat ill- 

 defined substance known as humus, which is also formed by 

 prolonged boihng of sugars with dilute acids. Humus bodies 

 are generally of an acid character, dissolving in alkahs to 

 form brown solutions. 



The Decomposition of Pectose Bodies. — This fermen- 

 tation has been studied by Wienogradski and his pupils, and 



