276 



THE MAINTENANCE OF THE INDIVIDUAL 



tVjermometer 



Energy Producers 



Carbohydrates, proteins, and fats are the sources from which energy 

 within the animal body is derived. Of these, carbohydrates and fats 



are more readily oxidizable than proteins, 

 a fact which is taken advantage of by 

 the Eskimo, who secures much of his 

 energy from oils and fats. The white 

 man in the tropics uses carbohydrates 

 chiefly for the same reason. 



No two foods contain the same per- 

 centages of carbohydrates, proteins, or 

 fats. At water analyzed many foods in 

 the calorimeter which bears his name. 

 Such a bomb calorimeter consists essen- 

 tially of an outer insulated chamber sur- 

 rounding one containing a known amount 

 of water. The inner compartment in 

 turn encloses the metallic chamber in 

 which a certain amount of oxygen and 

 food are placed and burned by means of. 

 an electric current. The amount of heat 

 generated is transmitted to the water in 

 the chamber surrounding the bomb and 

 the value of this in terms of calories 

 is then determined. It will be recalled 

 that a calorie is the amount of heat necessary to raise one gram of 

 water one degree centigrade. 



l— ^ater around, bomb 

 ■varmect by bixcmug' 

 of fooct 



Diagram of a bomb calorim 

 eleri How does it, work.^ 



Non-Energy Producers 



Three widely diversified groups are represented by water, inorganic 

 salts, and vitamins. All serve the common end of keeping the animal 

 in a state of well-being, yet each group does so in a very different way. 



Water constitutes a large portion of the animal body which may 

 compose even as much as five sixths of the daily intake. Estimates 

 vary from 62 to nearly 75 per cent of water by weight in the case of 

 the human body. The quantity in the different tissues varies accord- 

 ing to the metabolic state of the tissues of the organism. It is well 

 established that bone contains only about 22 per cent of water, while 

 other organs, as the liver, muscles, kidney, and brain, contain much 



