ASSIMILATION 



77 



contain the elements or compounds needed by the protoplasm for 

 its upkeep and normal functions. If we recall the chemical nature 

 of protoplasm, it will be evident that food must contain carbo- 

 hydrates, fats, hpins, proteins, water, and inorganic salts, or 

 materials from which these constituents can be made. Certain 

 organic compounds known as vitamins are also necessary. In 

 addition, atmospheric oxj-gen becomes a food, since it is essen- 

 tial for the oxidative reactions that are characteristic of proto- 

 plasmic functions. The chemical composition of carbohj^drates, 

 fats, lipins, and proteins has been indicated, and their occur- 

 rence in typical foodstuffs is shown by the following table: 



Examples of Composition of Food 

 (Adapted from Bulletin 28, U. S. Dept. Agriculture) 



Water 



Milk 



Egg 



Steak 



Fish (fresh mack- 

 erel) 



Butter 



Honey 



Sugar 



Corn flour 



Wheat flour 



Macaroni 



Dried peas 



Peanuts 



Tomatoes 



Asparagus 



Cabbage 



White potatoes. . . . 



Squash 



Sweet potatoes. . . . 



Green peas 



Oranges 



Apples 



Bananas 



87.0 

 74.0 

 67.0 



73.0 

 11.0 



20.0 



0.0 



13.0 



12.0 



10.0 



9.5 



9.0 



94.3 



94.0 

 71.5 

 75.5 

 88.3 

 69.0 

 74.6 

 86.9 



84.6 

 75.3 



Fat 



5.0 

 10.0 

 12.0 



7.0 

 85.0 



0.0 

 0.0 

 1.0 



1.0 

 1.0 

 1.0 

 39.0 

 0.4 



0.2 

 0.3 

 0.1 

 0.5 

 0.7 

 0.5 

 0.2 



0.5 

 0.6 



Organic 

 Accessories 

 (" vita- 

 mins ") 



iMin- 

 eral 



.salts 

 (ash) 



present 



abundant 



present 



present 

 some abun- 

 dant — oth- 

 ers absent 

 present 

 ab.scnt 

 nearl}^ ab- 

 sent 

 deficient 

 deficient 

 deficient 

 deficient 

 very abun- 

 dant 

 abundant 

 present 

 present 

 present 

 abundant 

 abundant 

 very abun- 

 dant 

 abundant 

 present 



0.7 

 1.0 

 1.0 



1.0 



3.0 



trace 

 absent 

 1.0 



0.5 

 1.0 

 3.0 

 2.0 

 0.5 



0.7 

 1.0 

 1.0 

 0.8 

 1.1 

 1.0 

 0.5 



Fuel 



value 



per 



pound 



325 

 720 

 900 



645 



3605 



1520 

 1810 

 1645 



1665 

 1665 

 1635 

 2560 

 105 



105 

 145 

 440 

 215 

 570 

 465 

 240 



290 

 460 



Early workers in the field of nutrition came to the conclusion 

 that the average adult man needed 500 grams of carbohydrates, 



