There has grown up, contemporaneously with the teachings of Freud,
a body of discoveries and knowledge in physiology, concerning
these factors, which is like a long sword of light illuminating a
pitch-black spot in the night. The dark places in human nature seem to
have become the sole monopoly of the Freudians and their psychology.
But only seemingly. For all this time the physiologist has been
working. Beginning with a candle and now holding in his hands the most
powerful arc-lights, he has explored two regions, the sympathetic
nervous system and the glands of internal secretion, and has come upon
data which in due course will render a good many of the Freudian
dicta obsolete. Not that the Freudian fundamentals will be scrapped
completely. But they will have to fit into the great synthesis which
must form the basis of any control of the future of human nature. That
future belongs to the physiologist. Already his achievements provide
the foundations. I propose in the following chapters to sketch the
history and outline the elements of this new knowledge, and then to
glimpse some of the larger human reactions to it. A good deal of this
new knowledge is not altogether new. A number of the isolated facts
have been known and talked about for more than two generations. But
the newer additions, and the light they have thrown upon old problems
present the opportunity for a synthesis, which must sooner or later be
made.

THE CHEMISTRY OF THE SOUL

Besides, it is time that the secrets of the laboratories stepped out
into the market place, unashamed. Imaginative man has played for ages
immemorial with wondrous fairy tales and fancies of what he would
achieve. The sciences of physics and chemistry have made everyday
commonplace realities out of his radiant dreams. One need not repeat