122 TEXT-BOOK OF PHYSIOLOGY 



has over a low protein diet (60 to 80 grams) lies in the fact that the former 

 has a greater stimulating effect on the general metabolic process than the 

 latter as shown by an increase in the heat produced and dissiqated from the 

 body. This action of protein is to be attributed, however, to the action of 

 some of the amino-acids set free during digestion and subsepuently found 

 circulating in the tissue fluids. In this situation they stimulate, by reason 

 of their chemic features, the activity of the tissue cells, whereby their power 

 to metabolize carbohydrates or fats is considerably increased. The experi- 

 ments of Lusk have shown that when amino-acids, e.g., glycocoll, alanin, etc., 

 are administered singly or combined to an animal, there is an increase in 

 heat production far beyond that which would result from oxidation of the 

 carbonaceous radical (glucose) which arises in the metabolism of the amino- 

 acids themselves; from this fact the inference is drawn that the increase in 

 metabolism, expressed in terms of heat, which follows the ingestion of meat 

 is to be attributed to the mass action of the absorbed amino-acids on the 

 tissue cells. For this reason proteins are said to have a specific dynamic 

 action on metabolism presumably beneficial. 



CLASSIFICATION OF FOOD PRINCIPLES 



Though the food principles are grouped as proteins, fats, carbohydrates, 

 etc., the members of each group differ somewhat in chemic composition, 

 digestibility, and nutritive value. These groups are as follows: 



1. PROTEINS 



Principle. Where found. 



Myosin Flesh of animals. 



Albumin, vitellin White of egg, yolk of egg. 



Caseinogen Milk. 



Serum albumin, fibrin Blood contained in meat. 



Gliadin and glutinin Grain of wheat and some other cereals. 



Vegetable albumin Soft-growing vegetables. 



Legumin Peas, beans, lentils, etc. 



2. FATS 



Animal fats In adipose tissue of animals. 



Vegetable oils In seeds, grains, nuts, fruits, and other 



vegetable tissues. 



3. CARBOHYDRATES 



Dextrose or grape-sugar 1 x f { 



Levulose or fruit-sugar j 



Lactose or milk-sugar Milk. 



Saccharose or cane-sugar Sugar-cane, beet roots. 



Maltose Malt and malted foods. 



g te k f Cereals, tuberous roots, and leguminous 



\ plants. 

 Glycogen Liver, muscles. 



4. INORGANIC 

 Water. 



Sodium and potassium chlorid. 



Sodium, potassium, and calcium phosphates 



and carbonates. 

 Iron. 



In nearly all animal and vegetable foods. 



5. VEGETABLE ACIDS 



Citric, tartaric, acetic, malic In fruits and vegetables. 



6. ACCESSORY FOODS 



Coffee, Tea, Cocoa, Condiments, Spices, Alcohol. 



