CELLULOSE. 231 



The Cellulose Group (C 6 H]oO 5 )x. 



Cellulose is that carbohydrate, or perhaps more correctly, mixture 

 of carbohydrates, which forms the chief constituent of the walls of the 

 plant-cells. This is true for at least the walls of the young cells, while 

 in the walls of the older cells the cellulose is extensively incrusted with a 

 substance called LIGNIN, and with many other cellulose derivatives and 

 compounds. 



The true celluloses are characterized by their great insolubility. They 

 are insoluble in cold or hot water, alcohol, ether, dilute acids, and alkalies. 

 We have only one specific solvent for cellulose, and that is an ammo- 

 niacal solution of copper oxide called SCHWEITZER'S reagent. The 

 cellulose may be precipitated from this solvent by the addition of acids, 

 and obtained as an amorphous powder after washing with water. 



Cellulose is converted into a substance, so-called AMYLOID, which 

 gives a blue coloration with iodine, by the action of concentrated sul- 

 phuric acid. With oxidizing agents (nitric acid, etc.) oxycelluloses are 

 produced. By the action of strong nitric acid or a mixture of nitric 

 acid and concentrated sulphuric acid, celluloses are converted into nitric- 

 acid esters or nitrocelluloses, which are highly explosive and have found 

 great practical use. 



The ordinary celluloses when treated at the ordinary temperature 

 with strong sulphuric acid and then boiled for some time after diluting 

 with water are coverted into glucose. In this case it must be observed, 

 according to MAQUENNE, that it is not maltose that is produced as an 

 intermediate step, but another disaccharide, called cellose or cellobiose. 



The cellulose, at least in part, undergoes decomposition in the intestinal 

 tract of man and animals. A closer discussion of the nutritive value 

 of cellulose will be given in a future chapter (on digestion). The great 

 importance of the carbohydrates in the animal economy and to animal 

 metabolism will also be given in the following chapters. 



Hemicelluloses are, according to E. SCHULZE/ those 'constituents of the cell- 

 wall related to cellulose which differ from the ordinary cellulose by dissolving 

 on heating with strongly diluted mineral acids, such as 1.25 per cent sulphuric 

 acid, and of yielding arabinose, xylose, galactose, and mannose instead of glucose. 

 Those hemicelluloses which serve partly as reserve food and partly as support- 

 substance, are very widely distributed in the plant kingdom. It must be recalled 

 that according to BIERRY and GIAJA 2 the digestive organs of different inverte- 

 brates (Helix, Astacus, Maja. Hommarus) contain enzymes which have an 

 energetic splitting action upon such polysaccharides as well as on the natural 

 celluloses. 



1 E. Schulze, Zeitschr. f. physiol. Chem., 16 and 19, with Castro, ibid., 36. 



2 Bioch. Zeitschr., 40, 370 (1912). 



