FOODS. 147 



liquid is called an emulsion. When cream is churned the 

 albuminous covering is removed and the butter "gathers." 



Cheese. Cheese is very rich in proteid, much more so 

 than lean meat. Yet, as it is rather difficult of digestion, 

 we do not use it largely as food ; we regard it more as a 

 luxury, while in many parts of Europe it is largely used as 

 food, taking the place of meat. It is a cheap food, and 

 might well be used more extensively, especially by laboring 

 men. When taken with milk it is said to be more readily 

 digested. 



Vegetable Proteids. Peas and beans (dried) contain 

 as much proteid (legumin) as meat, and all the cereals 

 contain some proteid (gluten). 



Fats. Fats are composed of carbon, hydrogen, and 

 oxygen. The oxygen is small in amount, so these foods 

 yield a great amount of energy by the oxidation of their 

 carbon (forming carbon dioxid) and hydrogen (forming 

 water). The fats most used are animal fats, including 

 butter. But some vegetable oils, such as olive and cotton- 

 seed oils, are used. 



The Carbohydrates. Starch and sugar are the chief 

 carbohydrates. Starch is used in larger quantity than any 

 other foodstuff except water. Sugar is usually regarded 

 as a luxury, yet it is an important food. It is quickly 

 absorbed. 



Carbohydrate-containing Foods. The principal car- 

 bohydrate-containing foods are the grains, vegetables, and 

 fruits. 



The Grains. The most important grains are wheat, 

 corn, rice, oats, rye, and barley. 



