468 PHYSIOLOGY. 



tion. These two processes are diametrically opposite to one another, 

 so that by virtue of the one the organism increases in bulk ; by virtue 

 of the other its bulk is diminished. 



By reason of the anabolic processes, the nonliving materials of 

 the food are converted into the complex molecules of the living tissues, 

 where they are stored up to form a store of potential energy. At any 

 time the organism is capable of transforming this potential energy into 

 kinetic, which is usually most conspicuous to the observer as heat and 

 motion. 



By this transformation, the complex tissues are broken down into 

 excretory products whose structure is simple. The waste materials 

 leave the cells to be carried by the lymphatics into the blood-stream, 

 ultimately to reach the exterior of the body, as excreta or as com- 

 ponents of some secretions. 



The two processes, anabolism and catabolism, taken conjointly, 

 constitute what is known as metabolism : an exchange of material. 



Normal metabolism thus requires the ingestion of a suitable 

 quality and quantity of food, which must be absorbed, assimilated 

 and stored within the tissues. In the latter place there must occur 

 the necessary transformation of the food in its now complex form, into 

 simpler products of an effete nature, evolving, at the same time, those 

 functions and activities which are common to the organism. In short, 

 all of the physiological phenomena demonstrable in the economy are 

 the result, either directly or indirectly, of anabolic or catabolic changes. 



Anabolic processes become visible during (1) the growth of the 

 body in infancy and adolescence, and (2) during convalescence from 

 a serious and debilitating disease. 



Gatabolic processes become evident during old age and in the 

 course of malignant diseases. Catabolism is the destruction of tissue, 

 from which process result the numerous manifestations of life. 



1. DUPLICATION : That is, the decomposition of an organic sub- 

 stance into two or more products whose sum represents exactly the 

 primitive substance. 



2. DEHYDRATION: This is a particular form of duplication in 

 which one of the products is water. 



3. OXIDATION : This is the most important part of the chemical 

 processes. By this means the decomposition is accomplished with . 

 fixation of oxygen, such as the decomposition of albumin, sugars 

 and fats. 



There is not a direct oxidation of the complex foods or tissues, 

 for these bodies undergo cleavage into simpler substances. It is these 





