Chapter 14 

 GROWTH AND THE AGING PROCESS 



by Warren Andrew 



It is perhaps natural in attempting any philosophical contemplation of the aging 

 process to ask ourselves, "How is growth related to aging?" The intimate relation 

 of the metabolic processes to so many of the features of the life of the organism 

 must come into consideration both in relation to growth and to aging. It seems 

 clear, for example, that for growth to occur, the rate of anabolism must be higher 

 than the rate of catabolism, in order that the complicated living substance may 

 increase in amount by the transformation of assimilated foodstuffs. Must the 

 reverse be true in the aging process? Must the rate of breakdown in old age, or the 

 period of decline, be more rapid than the rate of building vip? This question is 

 not as easy to answer, and we shall have more to say about it. Certainly this ques- 

 tion would seem to be one of critical importance in determining the relationship 

 between growth and the aging process. 



The problem which is posed here might also be expressed as follows: "Is 

 senescence a continuing part of the same general processes constituted by growth 

 and development? Is it truly the downward slope of a continuous curve? Do 

 growth and senescence constitute, as Flourens has said, an "uninterrupted chain"? 



To answer these questions we must attempt to see the processes of growth and 

 senescence in their relation to the pattern of the total life-history. First, we must 

 examine the chronological relationship of the two processes; second, we must 

 seek to find whether they may be occurring simultaneously or whether they are 

 mutually incompatible; and third, we must examine the characteristics — biolog- 

 ical, physical and chemical — of each. 



The growth of a living organism frequently has been compared with that of a 

 crystal, and the two usually have been contrasted, the statement being made that 

 the crystal grows by accretion, the acquisition of material by adding it to its sur- 

 faces, the organism by intussusception, the taking in of new materials and the trans- 

 formation of them within the organism into living substance. On closer stvidy, the 

 contrast in growth of the organism and of the crystal does not seem as sharp as at 

 first survey. Thus certain liquid crystals can grow by intussusception. The resto- 

 ration of a part of a crystal resembles to a certain extent the regenerative processes 

 in a plant or animal. Nor does a crystal always grow equally in all directions but, 

 like an organism, has its gradients of growth. 



One great contrast between the growth of the non-living crystal and the living 



