FUNCTIONS OF THE NUTRIENTS 165 



ceaseless and multiple activities of life on this planet are 

 sustained by an energy which comes to the plant in the 

 sun's rays and is stored there through the synthesis of 

 carbon compounds. 



242. Measurement of energy. It is obvious that if 

 the internal and external work performed by the animal 

 is sustained by the food, it is desirable to measure the 

 energy available in different feeding-stuffs, provided, 

 of course, that they differ in this respect. In order to 

 measure anything, we must have a standard or unit of 

 measurement. In this case it cannot be a unit of space 

 or of mass, that is, we cannot declare that corn meal con- 

 tains so many cubic feet or pounds of available energy. 

 Energy has neither dimensions nor weight. If we meas- 

 ure it at all, it must be by units of temperature or of work 

 performed. Units of this latter kind are the ones applied 

 to the measurement of food energy. The one that has 

 been most commonly used is the Calorie, this being the 

 energy which in terms of heat is sufficient to raise the 

 temperature of one pound of water 4 F. Expressed in 

 terms of work, the Calorie (large) is very nearly 1.53 

 foot-tons, or in other words, it is equivalent to the work 

 involved in lifting one ton 1.53 feet. Heat units are 

 expressed in both the large Calorie and the small calorie. 

 When the former is indicated, the word begins with a 

 capital letter. The Calorie represents 1,000 calories. 

 Armsby proposes the use of the term therm, which repre- 

 sents 1,000 Calories, which renders less cumbersome the 

 figures given for the energy of a ration. 



243. Determination of energy units in feeding-stuffs. 

 The total energy or heat units developed in the combus- 

 tion of feeding-stuffs is determined in an apparatus 

 called a calorimeter. The latest form of this device is one 



