302 Mary Davies Swartz, 



DEXTRANASES IN THE ANIMAL KINGDOM. 



Attempts to hydrolzye lichenin by animal enzymes have been uni- 

 formly unsuccessful. The most exhaustive researches were made by 

 Nilson (342), in 1893, partly with pure lichenin and partly with the 

 powdered lichen itself. Digestions were made -svith human gastric juice 

 for 24 hours, in neutral, acid, and alkaUne solutions; with pancreatic 

 extracts; with gastric juice followed by pancreatic extract; and with 

 these same extracts, using preparations treated with j per cent sodium 

 hydroxide solution for 24 hours before the digestion. Nilson signifi- 

 cantly remarks that this resistance to sugar-forming enzymes is worthy 

 of note, inasmuch as certain lichens have been considered valuable food 

 for man, and that it is hard to understand how reindeer utilize the car- 

 bohydrates of lichens. His negative results with animal enzymes have 

 been substantiated by Brown (334) — who found digestion with 0.2 per 

 cent to 0.4 per cent hydrochloric acid equally ineffective — and by 

 Saiki (346). Torup (347) reports that the dextran isolated from La- 

 minaria digitata by Krefting is not hydrolyzed by ptyalin, amylopsin 

 or diastase. 



DIGESTION AND UTILIZATION IN ANIMALS AND MAN. 



Interest in the digestibility of lichenin arises, not only from its use 

 in the diet of normal individuals, but in the possibility of its furnish- 

 ing a substitute for other carbohydrates in the diet of diabetics. 

 After this idea was set forth by Kiilz (305), in 1874, it is not surprising 

 to find, in 1879, the Italian physician Cantani,i and the Norwegian 

 physician Bugge^ reporting experiments in the use of Cetraria bread 

 for diabetics. Without any further observations than that the sugar 

 in the urine was not increased, the idea prevailed which Voit expres- 

 sed in his monograph on Nutrition in 1881 (348) and Poulsson repeated 

 in 1906 (344), that in some way or other, the "moss-starch," or 

 lichenin, was changed into sugar in the alimentary tract, and served as 

 a true nutrient. Poulsson undertook to verify this by feeding experi- 

 ments with two diabetics, but as Mendel (340) has taken pains to 

 point out, the results obtained, namely that 45-49 per cent of the car- 

 bohydrates of the Cetraria bread eaten were utilized, are unreliable, 

 since the carbohydrates of the faeces were calculated by difference, 

 instead of being determined directly by analysis. 



iCited by Poulsson (344). 



''Bugge, Forhandlingar i det medicinske selskap, Kristiania, 1879, p. 179 (cited by 

 Poulsson). 



