ALBERT SZENT-GYORGYI 
molecules, big or small, with the familiar ideas of shape, force, 
distance, charge, and the like. This classical biochemistry 
harvested the most wonderful triumphs. It has revealed the 
solid framework of life. It not only separated most of the single 
molecules, it was even capable of building many of them outside 
the living body with synthetic methods, providing medicine 
with a wonderful arsenal of substances, capable of improving 
human life by relieving a great deal of suffering. This science 
is still far from being exhausted and one of its greatest triumphs, 
only lately, was to start to break the genetic code which opens 
up the hope of looking deeper into ourselves, correcting short- 
comings, and perhaps even taking the further development of 
our race into our own hands. 
If I may refer at this point to my own modest work, I would 
mention the partial isolation of three substances from the 
thymus gland; one of these suppresses malignant growth, 
another is connected with that enviable state called “youth”’, 
and the third prevents conception. The latter two may be, 
perhaps, hormones of the thymus gland. It is too early to say 
more about them, but present experience gives a ray of hope 
that we may get closer to the solution of three major human 
problems (prevention of cancer, extension of youth and dealing 
with over-population). 
However, if we do not allow ourselves to be blinded by these 
successes, we can also perceive failures, which are rather dis- 
turbing. We do not know what life is but can distinguish, 
beyond a doubt, between a live cat and a dead one. We know 
life by its symptoms, like motion, reflexes or secretions. All 
these functions involve transduction of chemical energy into 
mechanical, electrical or osmotic work. We do not understand 
any of these processes by which mankind has known death from 
life since the dawn of his history. What makes this failure 
disturbing is that we make no real progress on this line. It 
looks as if biochemistry had built only a frame from which the 
picture is still missing. 
This failure was brought home to me during the past twenty 
years by the failure in my own work. More than twenty years 
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