228 CENTENARIANISM VI 



did survive might, some of them, enjoy a century of 

 life. This brings us to a second kind of longevity 

 also characterising species that which agrees with 

 what has been called " the lease of life," and which 

 we call potential specific longevity. The age to 

 which a creature would attain, supposing it to escape 

 all the dangers of youth, the diseases and accidents 

 which are lurking about the life -way, and to die 

 simply of old age, would represent the " potential 

 longevity" of that kind of plant or animal. Very 

 few beings ever manage to exhibit this certainly 

 very few men ; but men are sufficiently anxious about 

 the matter, and many have taken so much pains to 

 live long, by avoiding all dangers, that we have good 

 ground to suppose that the lease of life of the present 

 race of men is normally something between seventy 

 and one hundred years. Care may enable a man to 

 expend very nearly his full lease ; but nothing which 

 he can do, no power under heaven, can enable him to 

 add a day to that term, any more than by taking 

 thought a cubit may be added to his stature. And 

 now we see the relations which centenarians hold to 

 other men in this matter. They are not persons who 

 have taken more care than the less rare but equally 

 admirable octogenarians ; they have simply been 

 born with a greater potential longevity a longer 

 lease of life and they have had the good or bad luck 

 to remain tenants for very nearly as long as the lease 

 was good. It is impossible to guess how many, but 

 doubtless thousands of possible centenarians die 

 before they are a year old, and thousands more at all 



