Nutrition Investigations. 301 



Even in the lower plants, dextrans do not occur to any great extent. 

 They have been observed in bacteria (338), yeast (339), fungi (350), 

 and liverworts (337), but occur most abundantly in lichens and algae^ 

 the lichens, as already stated, yielding dextrans to which the names 

 lichenin, isolichenin, usnin, everniin, etc., have been given. Especial 

 interest is attached to the dextrans of Cetraria islandica (lichenin and 

 isolichenin) which together form 80-90 per cent of the total carbohy- 

 drates of this lichen, because of its abundance in northern lands and 

 its use there as a foodstuff; hence these carbohydrates have received 

 more attention from chemical investigators than any other dextrans. 

 Ever since Berzelius (333), in 1808, studied the hot water extract of 

 Cetraria islandica, and called the carbohydrate mixture so extracted 

 "moss-starch," on account of its giving a blue color with iodine, the 

 idea that it is, like starch, a valuable nutrient, has prevailed. That 

 this hot water extract contained two carbohydrates, one soluble in 

 cold water (isolichenin) and the other in hot, was demonstrated by 

 Berg (332) in 1873, who also showed that the blue coloration with 

 iodine was a property of isolichenin, but not of lichenin. Lichenin was 

 first found to yield dextrose by Klason, in 1886 (337). The next year 

 the two carbohydrates were more fully investigated by Honig and St. 

 Schubert (336), who have carefully reviewed the earUer literature on 

 this subject. That lichenin and isolichenin yield dextrose on hydroly- 

 sis, has been verified by Karl Miiller (341), Brown (334), and Ulander 

 (348) , who have also shown the hemicelluloses of the water-insoluble 

 part to consist of dextran, mannan, and galactan, with a small amount 

 of pentosan. Escombe's (335) observation that lichenin yields gal- 

 actose has proved to be incorrect. 



DEXTRANASES IN THE VEGETABLE KINGDOM. 



Honig and St. Schubert (336) subjected isolichenin to the action of 

 malt diastase, and observed a rapid disappearance of the iodine color 

 reaction, and the formation of a dextrin-like substance precipitable 

 by alcohol — a result verified by Brown (334) in 1898. Berg (332) 

 treated lichenin with malt diastase but was unable to observe any 

 change produced in it; his results also have been verified by Brown 

 (334). The only experiments in which sugar has been obtained from 

 lichenin by the action of vegetable enzymes have been carried out by 

 Saiki (346) with "Taka" diastase from Eurotium oryzae and inulase 

 from Aspergillus niger. 



^Cf. p. 255, also v. Lippmann, Chemie der Zuckerarten, Vol. I, pp. 215-220. 



