38 Feeds and Feeding. 



By this table we learn that 235 parts of lean meat when burued 

 in the calorimeter give off as much heat as 100 parts of fat. The 

 respiration-apparatus tests place the equivalent at 243 parts — a 

 very close agreement with the calorimeter. Starch evolves 

 almost as much heat as lean meat, and cane and grape sugar 

 somewhat more. 



61. Definition of terms.— The Calorie is a term which desig- 

 nates the amount of heat required to raise the temperature of one 

 kilogram of water 1° Centigrade (or one pound of water 4° 

 Fahr. ). If instead of the heat unit we use the unit of mechanical 

 energy, the foot- ton, then the Calorie corresponds to 1.53 foot- 

 tons; that is, its heat represents the energy required to raise a 

 weight of 1.53 tons one foot in height. In the following table is 

 summarized the average energy in one gram of each of the classes 

 of nutrients. 



Potential energy in nutrients of food. 



Calories. Foot-tona. 



In one gram of protein 4.1 6.3 



In one gram of fat (ether extract) 9.3 14.2 



In one gram of carbohydrates 4.1 6.3 



These figures mean that when a gram of protein, whether of 

 body substance or furnished in feeding stuffs, is consumed in the 

 body, it will, if transformed into heat, yield enough heat to raise 

 the temperature of 4.1 kilograms of water 1° C, or, if trans- 

 formed into mechanical energy, do the work executed by the 

 steam-engine in raising a weight of one ton 6.3 feet, or 6.3 tons 

 one foot. A gram of fat is shown to yield more than twice the 

 Calories or foot- tons yielded by a gram of protein or carbohydrates. 



Stated in another way, an ounce of protein in the form of lean 

 meat, or one of carbohydrates in the form of starch or sugar, if 

 transformed into heat, will raise the temperature of 113 pounds 

 of water 1° Fahr., while an ounce of fat yields heat sufiieient to 

 warm 256 pounds of water one degree. ' 



» This description is adapted from the report on the fuel value of feed- 

 ing stuffs by W. O. Atwater, Third Annual Report, Storrs School Agrl. 

 Expt. Station, 1890. The interested reader will find the subject most 

 entertainingly discussed by the same writer in the Century Magazine 

 for July, 1887. 



