FOODS 321 



raising one pound four degrees Fahrenheit. The fuel value of different 

 foods may be computed in a definite manner. This is done by burning 

 a given portion of a food (say one pound) in the apparatus known as 

 the calorimeter. By this means may be determined the number of degrees 

 the temperature of a given amount of water is raised during the process 

 of burning. 



The Best Dietary. — Inasmuch as all living substance contains 

 nitrogen, it is evident that proteid food must form a part of the 

 dietary; but proteid alone is not usable. We must take foods 

 that will give us, as nearly as possible, the proportion of the 

 different chemical elements as they are contained in protoplasm. 

 We must have a mixed diet which may contain several different 

 food materials. 



A growing person must take in a little more food each day than 

 is used up. In an ordinary day's work, a man uses up about two 

 hundred and sixty grams of carbon and nineteen grams of nitrogen. 

 This must be replaced in the correct proportion. More carbon or 

 more nitrogen than needed, would simply mean that some of the 

 organs of the body would have to work overtime to rid the body 

 of the unused material. It has been found as a result of studies of 

 Atwater and others, that a man who does muscular work requires 

 about one quarter of a pound of proteid, the same amount 

 of fat, and about one pound of carbohydrate to provide for 

 the growth, waste, and repair of the body and the energy 

 used up in one day. In addition to this, an ounce of salt and 

 nearly one hundred ounces of water are used. The amount of 

 food consumed varies with the age and occupation of the individ- 

 ual. A child of from five to six years needs only .5 of the food 

 required by a man doing muscular work. A growing boy of high- 

 school age, contrary to common belief, needs only between .7 

 and .8 of the food needed by an active man. People who lead a 

 sedentary life need much less food than those doing hard work; the 

 latter, on the other hand, need more food than a person who is only 

 moderately active. By means of the table on the following page 

 (modified from Atwater^), which shows the composition of some 

 food materials, the nutritive and fuel value of the foods may be seen 



^ W. O. Atwater, Principles of Nutrition and Nutritive Value of Food. U.S. Dept. 

 of Agriculture, 1902. 



hunter's BIOL. — 21 



