Eugenics and Genetics 
of their population on an extensive scale! If there are advant- 
ages in these techniques, and one society or nation does adopt 
them with marked success, this will accelerate adoption else- 
where. 
But the real difficulty will be the lack of biological under- 
standing of people at large; this will be an enormous handicap, 
especially in view of the tremendous rate of progress in biology 
which we expect to see in the next 20 or 30 years. 
Koprowski: Could I very briefly take up two questions Dr. 
Lederberg raised about the transplantation of organs? They 
are (1) the production of transplantation antigens from human 
tissues and organs in large amounts for conditioning to homo- 
transplantation and (2) the availability of tissue transplants in 
large quantities. 
I believe that transplantation antigens can be extracted from 
human organs and tissues, which can be preserved by creating 
“‘banks”’ of frozen tissues. The extraction of sufficient amounts 
of antigen (which does not need to be chemically pure) will be 
greatly facilitated by the fact that tissue culture systems 
provide us with facilities for making available almost unlimited 
amounts of human tissue revived from the frozen state. 
The availability for future generations of “ready-made”’ 
transplants of intact human organs such as heart or kidney may 
present a much more formidable problem. Perhaps, following 
the current use of plastic heart valves and arterial walls, it will 
be possible to construct plastic prostheses of heart or kidney 
which would be accepted by the human body and remain 
functional in it. 
Medawar: I agree with Dr. Lederberg’s remarks on the 
possible social dangers of replacement therapy. I have thought 
about them myself, and I think the reason why I haven’t called 
public attention to them is simply because one is apt to thrust 
these rather unpleasant things out of one’s mind. But I agree 
with him in general, and also with what he said in particular 
about possible solutions of the problems of transplantation. 
Pincus: I would like to take up one of the questions which 
Dr. Muller left unanswered: that is, if you are going to consider 
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