172 THE CARBOHYDRATES 



is not dependent upon the existence of an ethereal siHcate as 

 stated by Pringsheim.* 



That there is a close relationship between lichenin and 

 cellulose is shown by the work of Karrcr and Joos,t and also 

 by the fact that lichenin J can be converted by the action 

 of a lichenase contained in barley diastase into cellobiose, the 

 disaccharide obtainable from cellulose (see p. 119), and that 

 on acetolysis it yields, like cellulose, octacetycellobiose. When 

 lichenin is heated in glycerol at 240° it is converted into a 

 substance lichosan, an anhydride of glucose of the formula — 



, O , 



CH— CHOH . CHOH . CH . CH . CH.,OH 



! o 1 



Since cellulose may likewise be converted into a glucose 

 anhydride cellosan, hchenin and cellulose are both regarded 

 as products of associated glucose anhydrides. By a comparison 

 of the optical rotation in cuprammonia solution of cellulose 

 and lichenin, however, Hess § has shown that these two 

 substances are not structurally identical. The same conclusion 

 is reached by Herzog and Gonell H ; they were, however, able 

 to establish the identity of plant cellulose with that of animal 

 origin (Tunicin). Lichenin is widely distributed in nature and 

 has been found by Karrer and Staub ^ in Evernia vulpina, 

 Usnea harhata, Parmelia furfuracea, and in barley, oats, maize, 

 spinach, beans, hyacinth bulbs, and other plants. The same 

 authors have isolated from the ahmentary canal of the snail. 

 Helix pomatia, the enzyme lichenase which also occurs in 

 barley and other plants and can hydrolyse lichenin to glucose 

 in a few hours ; the enzyme is comparable with cytase which 

 attacks reserve cellulose, and for this reason they are inclined 

 to look upon lichenin as a reserve cellulose. The fact that a 



* Pringsheim and Kusenack : " Zeit. physiol. Chem.," 1924, 137, 265. 



t Karrer and Joos : " Biochem. Zeit.," 1923. 136, 537 ; " Helv. 

 Chim. Acta," 1924, 7, 144. 



t Pringsheim, Knoll, and Kasten ; " Ber. dent. chem. Gesells.," 1925. 

 58, 2135. Pringsheim : " Biochem. Zeit.," 1926, 172, 411. 



§Hess: "Zeit. angew. Chem.," 1924, 37. 993- 



\\ Herzog and Gonell : " Zeit. physiol. Chem.," 1924, M'? 63. 



\\ Karrer and Staub : " Helv. Chim. Acta," 1924, 7, 159. 



