Longevity of Man and his Tissues 
Harman in America has lately been trying to use anti- 
radiation drugs to reverse or delay the effects of normal ageing 
in mice. His results are, in my view, equivocal, but the idea is an 
interesting one. 
It leads me to the oldest and most elusive of human ambi- 
tions. “‘Ah quanta spes est lapidem sperare sapientium’’ wrote? Kaau 
von Boerhaave in 1737; “‘what a hope that is, to have the 
philosophers’ stone! To hold to an unfailing bodily health, a 
constant vigour and tranquillity of mind, to preserve these into 
a green and rugged old age, until without a struggle or a sick- 
ness body and soul part company: ... nay more, to regain lost 
youth—the old granddam to win back a merry suppleness... 
the wrinkles of her brow to fill and level, so that she straightens 
and she shines... even old moulted fowls to feather and lay 
eggs again. Yet alas for that fortunate hope: the nearer they 
win to it, so much the more does possession threaten present 
dangers to them that all but have it, and how these may be 
avoided I do not know.”’ 
It may not, of course, prove possible to avoid them, partic- 
ularly where the reversal of established senile change is 
concerned. Some biologists would share the pessimism recently 
expressed by Strehler3, who suggests that the only unity in age 
effects may be what I have elsewhere called a loss of programme, 
due to the failure of natural selection to secure homoeostasis at 
great ages. Such pessimism, although it may eventually prove 
correct, is less in evidence now than it was ten, or even five 
years ago. The operational attempt to interfere in age processes 
is now, at least, being taken seriously by people other than 
quacks and the obsessed; the number of teams clocking on daily 
to work on the project, in the United States alone, was over 800 
last year, and is going up there by about 200 a year. 
What has so far been achieved in this direction? In one sense 
very little, certainly not enough to make it possible yet to pre- 
dict either the feasibility of controlling our rate of ageing, or the 
pattern which such control would produce. There are still 
three major hypotheses of ageing in the field: that it is timed by 
the loss of irreplaceable cells and structures, that it results from 
aat 
