HUMAN FOODS. 



19a 



XII. HUMAN FOODS. 



COMPOSITION OF HUMAN FOOD MATERIALS.* 



(Atwater.) 



Ordinary food materials, such as meat, fish, eggs, pota- 

 toes, wheat, etc., consist of — 



Refuse. — As the bones of meat and fish, shells of shellfish, 

 skin of potatoes, bran of wheat, etc. 



Edible Portion. — As the flesh of meat and fish, the white 

 and yolk of eggs, wheat flour, etc. The edible portion con- 

 sists of water and nutritive ingredients or nutrients. 



The principal kinds of nutritive ingredients are protein^ 

 fats, carbohydrates, and tniiier rl ?natters. 



The water, refuse, and salt of salted meat and fish are 



called non-nutrients. In comparing the values of different 



food materials for nourishment they are left out of account. 



Classes of Nutrients. — The following are familiar examples 



of compounds of the four principal classes of nutrients. 



[ Albnviinoids, e.g., albumen (white of 

 I eggs); casein (curd)of milk; myosin, 

 the basis of muscle (lean meat) ; 

 Proteids. \ gluten of wheat, etc. 



Gelatinoids, e.g., collagen of tendons; 

 ossein of bones; which yield gelatin 

 Protein.^ I^ or glue, etc. 



Meats and fish contain very small quantities of 

 so-called '"extractives." They include kreatin 

 and allied compounds, and are the chief ingre- 

 dients of beef-tea and meat-extract. They 

 contain nitrogen, and hence are commonly 

 classed with protein. 

 Fats, e.g., fat of meat ; fat (butter) of milk ; olive-oil ; oil 



of corn, wheat, etc. 

 Carbohydrates, e.g., sugar, starch, cellulose (woody fiber), etc. 

 Mineral matters, e.g., phc^sphate of lime, sodium chlorid (com- 

 mon salt), etc. 



* Extracts from " Foods, Nutritive Value and Cost " (Farmers' Bulletin No. 

 ?3K and " Food and Diet " (U. S. Dept. of Agriculture Year Hook, 1804). See 

 also Farmers' Uull. No. 142, and-Circ. No. 4', Rev., Office of Exp. Stations. 



