234 ORGANIC AGRICULTURAL CHEMISTRY 



and in both plants and animals this energy is supplied by the 

 same food materials, carbohydrates, fats and proteins, which 

 undergo analogous metabolic reactions. As has been stated, 

 however, the entire function of food is the formation of body 

 substance and the liberation of the energy necessary for life. We 

 have given an example as to how much this energy amounts 

 to in man. In plants, while we cannot express the results in 

 definite figures, we can readily conceive of the magnitude, in 

 both body substance and energy, if we think of one of our 

 large trees. The mass of body material that has been built up 

 and the amount of energy expended to lift such a mass to the 

 height attained and to maintain it in position must both be of 

 very great magnitude. This material and this energy are 

 both supplied by the food of the plant. 



In the animal body we can easily measure and control the 

 food supply and we can also determine, to a large extent, the 

 energy expended. In plants, on the contrary, it is impossible 

 to do this and on this account the study of food metabolism 

 and the relation between food and energy has been almost 

 entirely studied in connection with animals. For this reason, 

 and because it is necessary first to understand this food and 

 energy relation of living organisms, we began our physiological 

 study with animals rather than with plants. 



Too much emphasis cannot be placed upon the fact that the 

 animal and the plant, as living organisms, are essentially the 

 same. Both build their body substance and obtain the energy 

 of their living processes by the metabolism of food consisting 

 of carbohydrates, fats and proteins. 



In connection with animals we have spoken of the inorganic 

 food materials consisting of certain inorganic salts. Some of 

 these are essential to the building of certain parts of the body 

 substance, while others act physiologically in the fluids of the 

 body. They are undoubtedly just as essential as the organic 

 foods, but they are not directly related to the energy supply 

 of the body. They are also used in much smaller amounts 

 and, being present in sufficient quantity in most foods, they do 



