162 BACTERIOLOGICAL AND ENZYME CHEMISTRY 



The solubility of cellulose in this reagent can be tested 

 by warming a few strips of filter paper in half a test-tube 

 full of Schweitzer's reagent until solution is practically 

 complete ; on acidification cellulose will be precipitated as a 

 flocculent precipitate. One of the technical processes for the 

 production of artificial silk is based on the solution of cellulose 

 in copper-ammonium solutions, and its re-precipitation under 

 conditions resulting in the production of fine fibres. 



It is possible to distinguish microscopically in a plant 

 section between cellulose and pectose, by dissolving out the 

 cellulose with a few drops of Schweitzer's reagent. 



The cellulose can be further distinguished from the pectose 

 by treatment with dilute iodine ; partially hydrated cellulose, 

 such as can be obtained by treatment of ordinary cellu- 

 lose with alkali, is stained blue by iodine. E.g., the cellulose 

 precipitated from solution in the foregoing experiment can 

 be coloured thus ; pectose bodies give no coloration. 



Coming now to the method by which cellulose and pectose 

 bodies are broken down in nature, we find in the case of cellu- 

 lose that this occurs by three well-defined processes : 



1. By the action of the enzyme cytase which is secreted 

 by cells and by various organisms. 



2. By fermentation under anaerobic conditions, that 

 is, in absence of air, through the action of certain specific 

 bacteria. 



3. By decomposition under aerobic conditions, through the 

 action of certain bacteria and moulds in presence generally of 

 nitrates. 



It is probable, of course, that the action of the organism in 

 the last two cases is due to secretion of a cellulose- dissolving 

 enzyme, but this has not so far been actually isolated. 



1. We may take these cases in order. It will be re- 

 membered that in the process of saccharification of starch, 

 which takes place in the development of the barley grain, the 

 cell walls of the endosperm are broken down and the interior 



