CARBOHYDRATES AXD RELATED BODIES. 49 



pure cellulose, as all the other bodies in the original fibers have 

 been removed by the bleaching and washing processes to which 

 the ra.w material was subjected in the manufacture of the 

 paper. A pure cellulose paper may be made from wood also, 

 but only by more complicated operations. 



The pure cellulose is characterized by insolubility in water, 

 weak acids, alkalies, alcohol or ether. It may be dissolved 

 rather readily in a solution known as Schweitzer's reagent 

 and by prolonged digestion with acids is converted into hexoses 

 and pentoses. 



The natural celluloses may be divided roughly into three 

 groups: (a) those which resist hydrolytic action very per- 

 fectly and are not capable of serving as foodstuffs for any 

 animals; in this group we have linen and cotton fibers, hemp, 

 China grass, etc. (b) Those which are less resistant to hydro- 

 lytic action and which contain active CO groups. These 

 bodies may be called oxycelluloses ; they yield also furfuralde- 

 hyde by distillation with hydrochloric acid. In this group 

 we have the mass of the material found in the fundamental 

 tissues of flowering plants, and a large part of ordinary woody 

 tissue. This lignified tissue is made up of compound celluloses 

 or lignocelluloses from which the cellulose proper may be 

 isolated in a variety of ways. Some of the bodies in this 

 group are partly digestible and have some value as foods for 

 the herbivora. (c) In this third group we have substances 

 described as pseudocelluloses or hemicelluloses and which offer 

 little resistance to hydrolysis. They are easily attacked by 

 weak acids and alkalies and also suffer digestion by enzymes, 

 so that they may be classed among the foodstuffs of limited 

 value for the herbivora. These bodies resemble starch much 

 more than they resemble the lignocelluloses. By action of 

 weak acids fermentable sugars are formed almost quantita- 

 tively from pseudocelluloses, while from the lignocelluloses 

 not over about 20 per cent of fermentable sugars may be 

 obtained. 



