precise inductions of a Darwin. If the mediaeval
Arabian endeavored to dull the knife of the surgeon with the use of
drugs, his results hardly merit to be termed even an anticipation
of modern anaesthesia. And when we speak of preventive medicine--of
bacteriology in all its phases--we have to do with a marvellous field of
which no previous generation of men had even the slightest inkling.

All in all, then, those that lie before us are perhaps the most
wonderful and the most fascinating of all the fields of science. As
the chapters of the preceding book carried us out into a macrocosm of
inconceivable magnitude, our present studies are to reveal a microcosm
of equally inconceivable smallness. As the studies of the physicist
attempted to reveal the very nature of matter and of energy, we have now
to seek the solution of the yet more inscrutable problems of life and of
mind.

I. THE PHLOGISTON THEORY IN CHEMISTRY

The development of the science of chemistry from the "science" of
alchemy is a striking example of the complete revolution in the attitude
of observers in the field of science. As has been pointed out in a
preceding chapter, the alchemist, having a preconceived idea of how
things should be, made all his experiments to prove his preconceived
theory; while the chemist reverses this attitude of mind and bases his
conceptions on the results of his laboratory experiments. In short,
chemistry is what alchemy never could be, an inductive science. But
this transition from one point of view to an exactly opposite one was
necessarily a very slow process. Ideas that have held undisputed sway
over the minds of succeeding generations for hundreds of years cannot
be overthrown in a moment, unless the agent of such an overthrow be so
obvious that it cannot be challenged. The rudimentary chemistry that
overthrew alchemy had nothing so obvious and palpable.

The great first step was the substitution of the one principle,
phlogiston, for the three principles, salt, sulphur, and mercury. We
have seen how the experiment of burning or calcining such a metal
as lead "destroyed" the lead as such, leaving an entirely different
substance in its place, and how the original metal could be restored by
the addition of wheat to the calcined product. To the alchemist this was
"mortification" and "revivification" of the metal. For, as pointed
out by Paracelsus, "anything that could be killed by man could also be
revivified by him, al