172 NUTRITION, DIETETICS AND ANIMAL HEAT 



Metabolism. By metabolism is meant those processes in the 

 body whereby food products are appropriated, their stored-up 

 energy utilized, and the waste discarded. 



Metabolism is divided into, (i) anabolism, and (2) katabolism. 

 Anabolism is the process of building up tissue by cell appro- 

 priation of food stuffs. Katabolism is the process of destroying 

 tissue in order to set free energy that the organs of the body 

 may perform their various functions. 



When the anabolic processes are equal to the katabolic there 

 is no excessive storage of material, but an individual remains 

 of uniform size, weight, and strength. If the anabolic are in 

 excess of the katabolic processes, the excessive products are 

 stored up in cells and an individual increases in size, weight 

 and strength. If the katabolic processes are in excess of the 

 anabolic there is a call on the tissues for the matter already 

 stored there and there is a decrease in strength, weight and 

 size. 



Death. As long as a cell appropriates enough to supply the 

 deficit caused by the destruction of material in the expenditure 

 of energy, the cell will live ; but when the intake cannot make up 

 for the output lost the cell ceases to functionate and this is called 

 death. 



Problems Involved in the Nutritive Process. Since the 

 actual changes occurring and the method of their production 

 cannot be understood, the question of nutrition resolves itself 

 into a consideration of the final fate of the various aliments, of 

 their relative value in nutrition, of conditions influencing the 

 process, and of the explanation of certain facts connected with 

 the destruction of the food-stuffs, particularly the production 

 of heat. 



The change which the foods finally undergo in the body is one 

 of oxidation. It is therefore chemical changes which give rise 

 to physical activity. Oxidation is accompanied by the produc- 

 tion of heat. The same sum total of heat is developed when a 



