46 ADVANCED PHYSIOLOGY 



such should not be considered as satisfactory substitutes for 

 fresh fruits. Again, in this connection, the necessity for a 

 varied diet is clearly emphasized. 



COMPOSITION OF COMMON FOODS 



Milk, taken alone, is a complete food, containing all nec- 

 essary materials. Its composition is approximately, proteid, 

 2.5%; fat, 4%; sugar, 5%; water, 88%. Milk should be 

 considered a food and not a beverage; it contains a higher 

 percentage of solids than any of the commonly used vegetables 

 except peas and beans. 



Butter is the fat of milk and little else. It contains prac- 

 tically no tissue building substances, but is useful to accom- 

 pany other foods, like bread, which are deficient in fat; 

 Fig. 21. 



Cheese contains all the proteid in milk, together with 

 most of its fat. There is almost no carbohydrate in it, how- 

 ever, and while very nutritious because of its high percentage 

 of proteid (30% or more), it should be eaten only with 

 other foods containing sugars or starches, e. g. bread 01 

 crackers. 



Meats always contain large amounts of proteid as well 

 considerable fat. They are among the most easily digesl 

 of the proteid foods. Meats contain no carbohydrates am 

 should not be eaten alone, but should be accompanied 

 some starchy foods, such as bread or potatoes. 



Eggs should be classed with meats since they contain about 

 the same kinds of material, and should be used in the same 

 way. 



Bread is one of the best foods. It contains considerable 

 proteid and a large amount of starch. The fat present is not 

 sufficient to make bread a balanced food, but we commonly 

 eat it with butter. Bread and butter alone make an almost 

 perfect diet. 



