30 PRESIDENT’S ADDRESS. 
reduction in population. There are races who have shown themselves 
able at a word to throw off all tradition and take into their service 
every power that science has yet offered them. Can we expect that 
they, when they see how to rid themselves of the ever-increasing 
weight of a defective population, will hesitate? The time cannot be 
far distant when both individuals and communities will begin to 
think in terms of biological fact, and it behoves those who lead 
scientific thought carefully to consider whither action should lead. 
At present I ask you merely to observe the facts. The powers of 
science to preserve the defective are now enormous. Every year 
these powers increase. This course of action must reach a limit. 
To the deliberate intervention of civilisation for the preservation of in- 
ferior strains there must sooner or later come an end, and before long 
nations will realise the responsibility they have assumed in multiplying 
these ‘ cankers of a calm world and a long peace.’ 
The definitely feeble-minded we may with propriety restrain, as 
we are beginning to do even in England, and we may safely prevent 
unions in which both parties are defective, for the evidence shows 
that as a rule such marriages, though often prolific, commonly produce 
no normal children at all. The union of such social vermin we should 
no more permit than we would allow parasites to breed on our own 
bodies. Further than that in restraint of marriage we ought not to 
go, at least not yet. Something too may be done by a reform of 
medical ethics. Medical students are taught that it is their duty to 
prolong life at whatever cost in suffering. This may have been right 
when diagnosis was uncertain and interference usually of small effect; 
but deliberately to interfere now for the preservation of an infant so 
gravely diseased that it can never be happy or come to any good is 
very like wanton cruelty. In private few men defend such inter- 
ference. Most who haye seen these cases lingering on agree that 
the system is deplorable, but ask where can any line be drawn. The 
biologist would reply that in all ages such decisions have been made by 
civilised communities with fair success both in regard to crime and 
in the closely analogous case of lunacy. The real reason why these 
things are done is because the world collectively cherishes occult 
views of the nature of life, because the facts are realised by few, and 
because between the legal mind—to which society has become accus- 
tomed to defer—and the seeing eye, there is such physiological 
antithesis that hardly can they be combined in the same body. So 
soon as scientific knowledge becomes common property, views more 
reasonable and, I may add, more humane, are likely to prevail. 
To all these great biological problems that modern society must 
sooner or later face there are many aspects besides the obvious ones. 
Infant mortality we are asked to lament without the slightest thought 
