208 MAN, THE ANIMAL 



The much heralded attempts to produce the 

 "eternal fountain of youth" for man by grafting 

 some interstitial cells from the testis of a young 

 man into the body of an old man, have met with 

 failure as they must because it is an attempt to 

 make a small part of the entire living machine 

 come under the control of a minute fresh stimulus. 

 The body of man has never been regulated ex- 

 clusively by any one internal secretion. There 

 are many of them, each doing its specific work, — 

 all regulating the normal changes in his body. 

 Some have their greatest importance in early 

 youth, others during adolescence, and still others 

 every time we eat. Man is abnormal when these 

 secretions do not act in their season, for some 

 accelerate, others retard until a delicate balance 

 is struck which we have come to define as the 

 normal for man. It is thus folly to expect that 

 the body will respond to secretions taken out of 

 their relation to all other conditions or that some 

 one will dominate over all others. What all such 

 studies really reveal that is important is the mar- 

 velous restrictions and limitations under which 

 man lives. In whatever attitude of mind one ap- 

 proaches this general theme, it throws a new light 

 on the wonderful organization of a living human 

 being. As soon as he departs from the delicate 

 balance that Nature has developed in him, he 

 departs in some concrete particular phase from 



