METABOLISM 137 



435. The danger mentioned in the previous question is much less if 

 the hay is sprinkled Hberally with salt and if the barn is very tightly 

 built. Explain. 



Note. — A silo is a large, tank-like structure, open at the top. Green 

 and living corn plants, chopped up into small pieces, are packed tightly 

 into the silo in the fall and fed to cattle during the winter. 



436. What prevents the contents of a silo from decaying? 



437. During the first few days after a silo is filled, its contents becomes 

 distinctly warm and then gradually cools off. Explain. 



438. Why is it necessary to have the walls of a silo built very tightly? 



439. If the contents of a silo is not packed down tightly, it is apt 

 to spoil. Why? 



440. Why does the upper layer in a silo usuallj^ decay? 



REFERENCE PROBLEMS 



62. Give an example of a plant rich in starch; in fat; in protein. 



63. Which will produce more energy per unit of weight, a carbohydrate 

 or a fat? Why? 



64. Does fat play a more important part in animal or in plant nutrition? 

 Explain. 



65. Why does a starchy food keep better than a fatty one? 



66. In general, how are "organic" substances to be distinguished from 

 "inorganic" ones? Why were these terms chosen? 



67. By wliat means does sugar become converted into starch? 



68. Explain just what has been the history of a piece of coal and why it 

 produces so much energy when burned. 



69. What non-gaseous and unusable waste products sometimes result 

 from plant metabolism, and what does the plant do with them? 



70. Do plants ever derive energy from the oxidation of other compounds 

 than those of carbon? 



71. Give the derivation of each of the following terms and explain in what 

 way it is appropriate: 



Metabolism Enzyme Respiration 



Digestion Assimilation Fermentation 



