30 AGE, GROWTH, AND DEATH 



age, any power over the changes which the years 

 bring to each of us, unless we understand clearly, 

 positively, and certainly, what these changes really 

 are. I think you will learn, if you do me the honour 

 to follow the lectures further, that the changes are 

 indeed very different from what we should expect 

 when we start out on a study of age, and that the 

 contributions of science in this direction are novel 

 and to some degree startling. We can begin to 

 approach this broader view of our subject if we pass 

 beyond the consideration of man. 



If we turn from man to the animals which we are 

 most familiar with, the common domestic quadrupeds, 

 we see that they undergo a series of changes not 

 very dissimilar to those which man himself must pass 

 through. An old horse, an old dog, an old cat, shows 

 pretty much the same sort of decrepitudes which 

 characterise old men. But when we pass farther 

 down in the scale to the fishes, or even to a frog, we 

 discover great differences. Do you think you could 

 tell a frog when it is old by the way it walks for it 

 never walks or a fish by the amount of hardening 

 of the lungs, when it has none ? Yet the lack of 

 lungs is characteristic of the fish. And what becomes 

 of the theory of arterial sclerosis when we go still 

 lower in the animal kingdom, towards its lowermost 

 members, and find creatures which live and thrive 

 and have lived and thriven for countless generations, 

 yet have no arteries at all ? They, of course, do not 

 grow old by any change of their arteries. But when 



