58 MAN, — THE ANIMAL 



season, sugar can be extracted and kept indefinite- 

 ly, while the energy of coal was formed in plant 

 cells back in the carboniferous geological period. 



The terms proteins, carbohydrates and fats, just 

 used, refer to the way that certain atoms are 

 grouped in the chemical molecule. A common 

 protein is white of egg or lean meat; while sugar 

 and starch represent the carbohydrates, and olive 

 oil and butter are typical fats. There are many 

 different kinds of food, but all can be classified 

 under one of these three groups. This does not 

 mean that all of the proteins or fats are identical — 

 they are not; but simply that the chemical ele- 

 ments, oxygen, hydrogen, carbon, etc., for 

 example, are united on a certain fundamental plan 

 with many variations. 



One might visualize this theoretical chemical 

 conception by taking six blocks of one size and 

 shape, ten blocks of another size and shape, and 

 five more differing from the first two sets. With 

 these twenty-one blocks various shaped buildings 

 might be made. The carbohydrate molecule 

 (CgHjoOg) contains six atoms of carbon, ten 

 atoms of hydrogen and five atoms of oxygen. The 

 blocks may be used to suggest that different results 

 can be secured by varying the arrangement of the 

 three parts of carbohydrates. In a similar way 

 one can understand how fats may be different. 

 Proteins are much more complex and consequently 



