CHAPTER XIII 

 THE ORIGIN OF FOOD 



79. Organic foods destroyed. When proteins, fats, and car- 

 bohydrates become assimilated, they are still available as food 

 for other living beings. But when any of this material becomes 

 oxidized, it is thrown out of the world of living things. The 

 question may then be raised, If livirjg matter can continue to 

 live only at the expense of other living matter, and if living 

 matter is constantly being destroyed (oxidized), how can the 

 total amount of protoplasm be maintained, to say nothing of 

 the amount of live matter being increased ? 



80. The making of organic food. It is obvious that some- 

 where in the circle of feeding, new foods must be admitted 

 into the world of living things from the world of non-living 

 things. The answer to the question was found in the discovery 

 that the green parts of plants are active in the manufacture of 

 new organic foods. 



81. A manufacturing process. The process by which organic 

 materials are built up (chemically) out of inorganic materials 

 may be compared to a manufacturing process. In every such 

 process certain factors are essential. There must be (i) raw 

 material, (2) tools or machines for working on the material, 

 and (3) energy for driving the tools or machines. 



In addition to these factors, we can understand that there 

 is (4) a main product and sometimes material left over, called 

 "waste," or, better, (5) the by-product. 



82. Factors in starch-making. What are the factors in the 

 process of starch-making ? 



The raw materials used by the plant are found to be water 

 and carbon dioxid. 



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