52 STUDIES IN PHYSIOLOGY 



practical purposes a calorie 1 may be roughly described as the 

 amount of heat required to raise the temperature of a pound of 

 water through four degrees Fahrenheit. The fuel value of one 

 pound of each of the nutrients is as follows : proteids, 1820 

 calories ; carbohydrates, 1820 calories ; fats, 4040 calories. 

 On comparing these figures, we see that proteids and carbo- 

 hydrates have equal value in generating heat, while the fuel 

 value of fat is two and a half times as great. 



The heat-producing power or fuel value of each of the foods 

 (in Fig. 13) is indicated by the narrow black line ; the second 

 row of figures at the top of the chart (400, 800, etc.) repre- 

 sents the number * of calories. Thus the fuel value of a 

 pound of milk is about 300 calories ; a pound of butter, on 

 the other hand, will generate nearly 3500 calories of energy. 



Uses of Mineral Matters and Water. The mineral mat- 

 ters like the phosphates of lime and magnesium are neces- 

 sary for making bone. Salt is used in large quantities by 

 all civilized nations ; it makes foods more palatable, and it 

 is important in the processes of digestion. Water, as we 

 have learned, is an essential constituent of protoplasm, and 

 hence the body needs it constantly. A large amount is 

 supplied by the water contained in our solid foods, and we 

 get the rest from the milk, tea, coffee, and from the water 

 that we drink. 



5. COOKING OF FOODS 



Importance of Proper Cooking. Some of our foods, like 

 milk, nuts, and fruits, are eaten without being cooked. The 

 great majority, however, before they are taken into our 

 bodies are changed considerably. It is important for us to 

 learn the essential principles of good cooking, since food, 

 as often prepared, loses much of its flavor, becomes more or 

 less indigestible, and is deprived of a considerable percent- 

 age of its nutrition. 



Methods of cooking Meats. In civilized communities meats 

 are rarely eaten raw. They are usually cooked by broiling, 



