540 MISCELLANEOUS FARM SUBJECTS 



ecus materials, as the muscles and tendons, and supply the albu- 

 minoids of the blood, milk, and other fluids. 



The albuminoids of food are transformed into the albumi- 

 noids and gelatinoids of the body. 'Muscle, tendon and cartilage, 

 bone and skin, the corpuscles of the bloo.d, and the casein of milk 

 are made of the albuminoids of food. The albuminoids are some- 

 times called "flesh formers" or "muscle formers," because the lean 

 flesh, the muscle, is made from them, though the term is inadequate 

 as it leaves out of account the energy-furnishing function of protein. 

 The gelatinoids of food, such as the finer particles of tendon and the 

 gelatin, which are dissolved out of bone and meat in soup, though 

 somewhat similar to the albuminoids in composition, are not be- 

 lieved to be tissue formers. They are valuable in protecting the 

 albuminoids from consumption. The proteids can be so changed 

 in the body as to yield fats and carbohydrates, and such changes 

 actually occur to some extent. 



Protein as Fuel for the Body. The protein compounds are 

 also burned directly in the body like the carbohydrates, and thus 

 render important service as fuel. A man can live on lean meat. He 

 can convert its material into muscle and its energy into heat and 

 muscular power, but such a one-sided diet would not be best. 



Fats and Carbohydrates as Fuel. Fats and carbohydrates are 

 the chief fuel ingredients of food. Sugar and the starch of bread 

 and potatoes are burned in the body to yield heat and power. The 

 fats, such as the fat of meat and butter, serve the same purpose, only 

 they are a more concentrated fuel than the carbohydrates. The 

 body can also transform carbohydrates of food into fat. The dif- 

 ferent nutrients can to a greater or less extent do one another's 

 work. If the body has not enough of one kind of fuel it can use 

 another. But, while protein can be burned in the place of fats and 

 carbohydrates, neither of the latter can take the place of the albumi- 

 noids of protein in building and repairing the tissues. 



VALUE OP FOOD FOR SUPPLYING ENERGY. 



Heat and muscular power are forms of force or energy. The 

 energy latent or hidden in the food is developed as the food is con- 

 sumed in the body. The process is more or less akin to that which 

 takes place when coal is burned in the furnace of the locomotive. 

 For the burning of the food in the body or the coal in the furnace, 

 air is used to supply oxygen. When the fuel is oxidized or burned 

 be it meat or wood, bread or coal, the latent energy becomes active, 

 is transformed into power and heat. As various kinds of coal differ 

 in the amount of heat given off per ton, so various kinds of food 

 differ in amounts of energy. 



The processes of oxidation burning of material and transfor- 

 mation of energy in the body are less simple than in the engine 

 and less clearly understood. Late research, however, has given 

 ways of measuring the energy latent in coal, wood, and in food ma- 

 terials as well. The amount of heat given off in the oxidation of a 

 given quantity of any material is called its "heat of combustion," 



