HYGIENIC ASPECTS OF NUTRITION 265 



experiments) on from 40 to 50 grams (from li to 2^ ounces) 

 of protein per day. Of course other foods were supplied with 

 the protein foods. 



It is safe to say that the following represents an average 

 distribution of foods in making up a proper day's diet : pro- 

 tein, 118 grams; fats, 56 grams ; carbohydrates, 500 grams. 

 These amounts may vary greatly, according to personal habits, 

 the kind of work in which one is engaged, and the climate. 

 Men engaged in hard physical work in cold climates demand 

 larger quantities of food than here given, and a larger propor- 

 tion of fats, while people in tropical regions may work better 

 with smaller amounts of fats and more carbohydrates. In the 

 same way, the quantity of water needed varies in different 

 climates and with different occupations. The proportionate 

 composition of different kinds of food is shown in the tables 

 in section 260. 



292. Contaminated food. Nearly all kinds of food may 

 become the growing place for bacteria or other organisms 

 that will, if allowed to continue to grow, finally bring about 

 the decay of the food. A review of what was said on this 

 point in connection with the discussion of the bacteria and 

 molds (Chapter VIII) will prove helpful. Sometimes these 

 decay-producing organisms are dangerous to human health 

 and sometimes they are not. For example, the blue molds 

 that grow in Roquefort cheese, or the bacteria that ripen 

 other kinds of cheese, are not unwholesome and indeed are the 

 causes of the desired flavors of the different kinds of cheese. 



To prevent the decay of foods, preservatives are sometimes 

 used. Small amounts of formalin, benzoate of soda, or other 

 chemicals may be put into the liquid foods, as milk, and will 

 prevent decay; but while from superficial examination such 

 foods may appear to be good, they may at the same time con- 

 tain enough of the preservative to prove injurious. When 

 milk under exposure to the temperature of ordinary air does 

 not begin to sour within twenty-four hours, it is time to have 



