NOTES ON CETRARIA ISLANDICA. 187 



It will be observed that the quantity of proteids present must 

 be small at most. The bulk of the material is made up of 

 soluble carbohydrates. The latter were early made the subject 

 of chemical investigation. Without attempting to recite the 

 older and somewhat conflicting observations, we may refer to 

 the more recent results of Hb'nig and St. Schubert.* These 

 investigators conclude that extracts of Cetraria, obtained with 

 hot water, contain two carbohydrates. The chief one of 

 these, lichenin, forms a difficultly soluble jelly in cold water, 

 an opalescent solution in hot water, is not colored blue by 

 iodine, and does not rotate polarized light ; on boiling with 

 dilute acids lichenin yields crystallizable dextrose in addition 

 to dextrins. The second carbohydrate, called lichenin starch, 

 is regarded by these authors as a soluble modification of 

 ordinary starch. It has also been called isolichenin.f MunkJ 

 states that lichenin is most nearly related chemically to starch, 

 and that it probably undergoes the same fermentative changes 

 in the alimentary canal as are produced by boiling with dilute 

 acids. The following experiments by the writer confirm in 

 part and extend previous observations. 



Lichenin. Preparation. The dry assorted Iceland moss 

 was heated in a steam sterilizing apparatus for several hours 

 with a considerable quantity of water, and the extract then 

 filtered on hot water funnels. The cool filtrates deposited a 

 thick jelly which was thrown upon filters and allowed to 

 drain. The gelatinous mass was redissolved in hot water and 

 reprecipitated repeatedly until the cold filtrates as well as the 

 jelly no longer gave any blue coloration with iodine. The 

 gelatinous substance was next treated with warm alcohol until 

 all coloring matter was removed, then extracted with ether 



* Honig und St. Schubert, Sitzungsb. d. k. Akad. d. Wissenschaften zu 

 Wien, 1887, xcvi, 2te Abth., p. 685. The older literature is referred to here. 

 Cf. also Beilstein, Handbuch der organ. Chemie, 3te Auflage, i, p. 1098. 



t Cf. Beilstern, loc. cit., p. 1099. 



t Munk, J., und C. A. Ewald, Die Ernahrung des gesunden und kranken 

 Menschen, 1895, p. 102 ; also C. Voit, Die Ernahrung. Hermann's Handbuch 

 der Physiologic, 1881, vi, p. 413. 



