188 THE CONTROL OF LIFE 



manent framework within which the vital processes of 

 metabolism occur. This framework is built up of rela- 

 tively inactive constituents, and it is difficult to keep 

 these young. The vital current deposits materials in 

 its flow, and the bed begins to slow the stream. Every 

 now and then there may be a flood and a fresh erosion 

 — a fortnight's walking tour — but there are limits to 

 this. It is the laboratory apparatus that gets exhausted, 

 rather than the materials or the chemist within. Pro- 

 fessor Child, our greatest authority on the subject, 

 says : " For his high degree of individuation man pays 

 the penalty of individual death, and the conditions 

 and processes in the human organism which lead to death 

 in the end are the conditions and processes which make 

 man what he is." Perhaps we may say that natural 

 death was the price paid for having a body at all, and 

 that senescence is the tax on a body worth having. 



We have sympathy with those who wave aside our 

 biological theories of senescence and rejuvenescence 

 and demand a recipe for remaining young. That is 

 the really interesting aspect of the problem. 



Now the greatest authority on this subject was 

 Metchnikoff, who died in 1916, and not so very old 

 either. His conclusion, well grounded in fact, was that 

 if man lived a more careful and more temperate 

 life, and had a more enlightened understanding of the 

 limitations and disharmonies of his constitution, he would 

 no longer, as Buffon said, die of disappointment, but 

 would everj^here attain a hundred years. The two 

 poisonings that age us most, he said, are those of alco- 



