FOOD 205 



without proteids. The chief proteids are the gluten 

 of all cereals, peas, potatoes, beans, and lentils; the albu- 

 min in white of egg, milk, and blood; globulin from yolk 

 of egg and blood; myosin found in lean meat; casein in 

 milk and cheese; fibrin in clotted blood. Though certain 

 vegetables (as beans and peas) contain more proteid than 

 does meat, they furnish it in a less digestible form, that 

 is, a considerable part of it passes from the body unaf- 

 fected by the digestive processes, and the proteid of these 

 vegetables is therefore less valuable as food. 



Since only the proteids contain nitrogen, they are called 

 nitrogenous foods ; and carbohydrates and fats are called 

 nonnitrogenous. 



A healthy, well-fed animal is found to lose by excretion 

 as much nitrogen daily as is supplied in his food. If the 

 food contains an insufficient amount of nitrogen, the quan- 

 tity excreted is greater than that received, and the tissues 

 waste away. 



291. Fats are found in butter, milk, cheese, and meat, 

 in some of the grains, and in oils. They contain carbon, 

 hydrogen, and oxygen. They are oxidized in the body, 

 and furnish energy and heat. 



292. The Carbohydrates, like the fats, contain carbon, 

 hydrogen, and oxygen; but the proportion of oxygen is 

 larger than in fats. The carbohydrates include (1) starch, 

 which is found in cereals, vegetables, nuts, etc. ; (2) sugars 

 of different kinds, grape sugar, cane sugar, malt sugar, 

 and milk sugar, besides sugar manufactured from starch; 

 and (3) cellulose, found in fruits, cereals, and all vegetables. 

 Carbohydrates are very rapidly oxidized in the body, pro- 

 ducing heat, and it is they that are used up in the setting 

 free of energy when the muscles are vigorously exercised; 

 for it is found that the nitrogenous waste does not increase 



MACY'S PHYS. 13 



