44 LECTURE III. 



In discussing fruit-sugar we met with a reserve-carbohydrate, inulin, 

 which in its biological relations completely corresponds to starch. It 

 is found in the roots of Inula Hehnium, the bulbs of dahlias, etc., and is 

 different from starch in so far as it yields on hydrolysis fructose instead 

 of glucose. Furthermore, inulin dissolves in warm water without forming 

 a paste; iodine colors it yellow, and diastatic ferments do not attack it. 



Finally, in many lichens, especially in Iceland-moss, another kind of 

 starch is recognized which likewise is colored yellow by iodine; it dissolves 

 in hot water, and yields glucose upon complete hydrolysis. This is lichenin, 

 and, like inulin, it is not effected by diastatic ferments. 



Besides these carbohydrates which are found in the reserve-stores of 

 plants, others, such as amylin, lavosin, cerosin, and secalin, are found in 

 grain-seeds. These substances yield, as a result of hydrolytic decom- 

 position, sometimes glucose and sometimes fructose. In the constructive- 

 tissue of Lupinus luteus is found galactin, a carbohydrate of this group 

 yielding only galactose upon complete hydrolysis. Again, in the class of 

 graminese, palms, liliacese, amaryllidacese, iridese, and also in the many 

 dicotyledons, we meet with the so-called reserve-celluloses. We under- 

 stand by the term reserve-carbohydrates, substances which appear as solid 

 deposits on the cell-membrane of constructive tissue in seeds. 



The dextrins are usually regarded as forming a particular class in the 

 group of carbohydrates. They are, as has been stated, decomposition 

 products, and are obviously mixtures of substances with different molecular 

 weights. They form a transition stage between the " reserve-carbohy- 

 drates " and the " metabolic carbohydrates." By further hydrolysis 

 they yield molecules of glucose. 



Glycogen is to the animal organism what starch is to plants. We have 

 to thank the French scientist Claude Bernard l for its discovery, who in 

 1848 noticed the high sugar content of liver, and found sugar only absent 

 from it after prolonged starvation. A few years later, the same inves- 

 tigator succeeded in showing that the sugar observed in liver was not 

 directly present as such, but was formed gradually from a preliminary 

 state. He established the fact that by taking the liver from a dog right 

 after it is killed, the blood being washed off and the washing continued 

 in running water for forty minutes, then the last wash-water will no longer 

 show the presence of sugar. Even if a piece of such liver is boiled in 

 water, no sugar will be dissolved out of it. If, however, the liver is allowed 



1 See Bernard and Barreswil: Compt. rend. 27, 514 (1848); also E. F. W. Pfluger: 

 "Das Glykogen und seine Beziehungen zur Zuckerkrankheit," Bonn, Martin Hager 

 (1905) and Max Cremer: "Physiologic des Glykogens," in Ergeb. Physiol. (Asherund 

 Spiro) 1, 803 (1902), Wiesbaden, published by T. F. Bergmann. A complete summary 

 of Bernard's work is found in "L'reuvre de Claude Bernard," Paris, T. B. Bailliere 

 et Fils. 



