rtain kinds of oxidation to take place, just as water itself induces
a simpler kind of oxidation, and they would have a mechanical
explanation of the life activities. It was certainly not a very absurd
assumption to make, that this substance protoplasm could have this
power, and from this the other vital activities are easily derived.

In other words, the formulation of the doctrine of protoplasm made it
possible to assume that _life_ is not a distinct force, but simply a
name given to the properties possessed by that highly complex chemical
compound protoplasm. Just as we might give the name _aquacity_ to the
properties possessed by water, so we have actually given the name
_vitality_ to the properties possessed by protoplasm. To be sure,
vitality is more marvelous than aquacity, but so is protoplasm a more
complex compound than water. This compound was a very unstable compound,
just as is a mass of gunpowder, and hence it is highly irritable, also
like gunpowder, and any disturbance of its condition produces motion,
just as a spark will do in a mass of gunpowder. It is capable of
inducing oxidation in foods, something as water induces oxidation in a
bit of iron. The oxidation is, however, of a different kind, and results
in the formation of different chemical combinations; but it is the basis
of assimilation. Since now assimilation is the foundation of growth and
reproduction, this mechanical theory of life thus succeeded in tracing
to the simple properties of the chemical compound protoplasm, all the
fundamental properties of life. Since further, as we have seen in our
first chapter, the more complex properties of higher organisms are
easily deduced from these simple ones by the application of the laws of
mechanics, we have here in this mechanical theory of life the complete
reduction of the body to a machine.

==The Reign of Protoplasm.==--This substance protoplasm became now
naturally the centre of biological thought. The theory of protoplasm
arose at about the same time that the doctrine of evolution began to be
seriously discussed under the stimulus of Darwin, and naturally these
two great conceptions developed side by side. Evolution was constantly
teaching that natural forces are sufficient to account for many of the
complex phenomena which had hitherto been regarded as insolvable; and
what more natural than the same kind of thinking should be applied to
the vital activities manifested by this substance protopl