102 



THE CHEMICAL COMPOSITION OF THE BODY 



With amylolytic enzymes, the change practically only goes as far as the 

 maltose stage. 



Glycogen (animal starch) is the reserve form of carbohydrates in 

 animals. It is synthesized from dextrose and can again be hydrolyzed to 

 dextrose for transportation or for oxidation to yield energy to the tissues. 

 The following table shows the per cent, and distribution of glycogen in the 

 various tissues of the dog (Schondorff) : 



It occurs in relatively large amounts in some invertebrates, especially 

 in moluscs and in intestinal worms. The adductor muscle of the scallop 

 (Pecten irradians) is very rich in this substance. 



Glycogen resembles starch in forming opalescent solutions. It may be 

 prepared from the liver or muscle of a freshly killed animal by boiling the 

 tissue to coagulate the proteins, grinding with sand, boiling with water 

 slightly acidified with acetic acid and precipitating the filtrate with an excess 

 of alcohol; dilute or concentrated solutions of caustic alkalies may be used 

 to extract all the glycogen. Glycogen is a white, tasteless, and amorphous 

 powder. It gives a maroon color with iodine, and does not reduce alkaline 

 copper sulphate solution. It is completely precipitated by saturating its 

 solution with solid ammonium sulphate, by tannic acid, or by ammoniacal 

 basic lead acetate. On hydrolysis with mineral acids or on digestion with 

 amylolytic enzymes it yields the same series of products as ordinary starch. 



Inulin is the reserve carbohydrate of the Composite, occurring in the 

 tubers of the artichoke and dahlia and in the roots of the dandelion and bur- 

 dock. On hydrolysis with acids or the enzyme inulase, it yields levulose. 

 Inulin is slightly soluble in cold and easily soluble in hot water. It is precipi- 

 tated from its solution by an excess of alcohol. The starch-digesting enzymes 

 of the body do not act on inulin. 



Lichinin is obtained from the Cetraria Islandica (Iceland moss) . It forms 

 a difficultly soluble jelly in cold water and an opalescent solution in hot water. 

 On hydrolysis with dilute acids, it yields dextrines and dextrose. The 

 ordinary digestive enzymes have no action on lichinin. 



