72 THE CARBOHYDRATES. 



maltose, isomaltose, and glucose. On boiling with dilute acids also 

 glucose is formed, with various dextrins as intermediary products. 

 Among these, as has been shown, erythrodextrin is apparently the 

 first to develop, achroodextrin appears later, and from this isomaltose, 

 maltose, and glucose are finally obtained. It appears, however, that 

 during the decomposition of achroodextrin still other dextrins of 

 lower molecular weight are simultaneously formed, which in turn 

 yield maltose and glucose. Finally a dextrin is obtained which 

 undergoes no further change, and is termed maltodextrin. This 

 would correspond to the polypeptid which results from the albumin- 

 ous molecule through the action of trypsin and which similarly 

 withstands the further action of the ferment. The other dextrins 

 would correspond to the albumoses and those polypeptids which are 

 ultimately split into the component amino-acids, while glucose would 

 be comparable to these directly. 



Most characteristic is the behavior of starch toward iodine, with 

 which it gives an intense blue color that disappears on heating, but 

 reappears on cooling. In a solution of sodium or potassium hydrate 

 starch swells up and forms a paste. 



Dextrins. The dextrins, as has been shown, are formed from 

 starch during its hydrolytic decomposition by means of ferments or 

 on boiling with dilute mineral acids. To a certain extent they 

 result also when starch is heated to a temperature of from 200 

 to 210 C. Through continued decomposition they give rise to 

 maltose and isomaltose, and finally to glucose. 



As a class the dextrins are easily soluble in water and turn the 

 plane of polarization to the right. From the other polysaccharides 

 they diifer in their ability to dissolve cupric hydroxide in alkaline 

 solution. With erythrodextrin iodine strikes a red color, while 

 achroodextrin is unaifectd. 



Glycogen apparently plays the same role in the animal metabolism 

 which starch does in the vegetable world. It is accordingly also 

 termed animal starch. In this form carbohydrate material is largely 

 stored in the liver and the muscles. Its ultimate decomposition- 

 product is exclusively glucose, while dextrins and maltose are 

 formed as intermediary products. Its properties will be considered 

 in a future chapter. 



Inulin and lichenin occur in the roots of various composites 

 (Inula helenium, the dahlias) and in lichens (Icelandic moss) 

 respectively. Both are soluble in hot water and are colored yellow 

 with iodine, and neither is attacked by diastase. On hydrolysis 

 inulin yields Isevulose and lichenin glucose. 



Celluloses. As food-stuffs the celluloses are unimportant. They 

 are considered at this place owing to their wide distribution in the 

 vegetable world, where they form the greater portion of all cell- 

 envelopes. In the animal world they are likewise encountered, and 

 enter largely into the composition of the external skeleton of the 

 tunicates. They are characterized by their extreme resistance to 



