102 THE CHEMICAL COMPOSITION OF THE BODY 



It occurs in relatively large amounts in some invertebrates, especially 

 in moluscs and in intestinal worms. The muscles and reproductive organs of 

 oysters, clams, and scallops are 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 nitrate 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 Composites, 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 digestive 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. 



Cellulose forms a large portion of the cell wall or the woody structure 

 of plants. It is extremely insoluble. Chemically, it is more complex than 

 the common starch molecule. The hydrochloric and hydrofluoric acid 

 extracted (ash-free) filter-papers and absorbent cotton are examples of prac- 

 tically pure cellulose. 



INORGANIC SUBSTANCES OF THE BODY. 



Salt. The inorganic principles of the human body are numerous. 

 They are derived, for the most part, directly from food and drink and pass 

 through the system unaltered. Some radicals are newly formed by oxi- 

 dation within the body, as, for example, a part of the sulphates and car- 

 bonates from the sulphur of the proteins and the carbon of protein, fat, and 

 carbohydrate. 



Much of the inorganic saline matter found in the body is a necessary 

 constituent of its structure, as necessary in its way as protein or any other 

 organic principle. Another part is important in regulating or modifying 

 various physical processes, as absorption, solution, and the like. A part 

 must be reckoned only as matter which is, so to speak, accidentally present, 

 whether derived from the food or the tissues, and which will, at the first 



