nt parts. It is certainly true that organic
evolution cannot be controlled in the same way by men, and that science
has not yet found out what all the factors are. And yet we are going to
learn in a later discussion that nature's method of transforming organisms
in the course of evolution is strikingly similar to the human process of
trial and error which has brought the diverse modern mechanisms to their
present conditions of efficiency. This matter, however, must remain for
the time just as it stands. The first objection, namely, that an organism
ought not to be viewed as a machine, is one that we must meet immediately,
because it is necessary at the very outset to gain a clear idea of the
essentially mechanical nature of living things and of their relations to
the conditions under which they live. It is only when we have such a clear
understanding that we can profitably pursue the further inquiries into the
evidence of evolution. Our first real task, therefore, is an inquiry into
certain fundamental questions about life and living things, upon which we
shall build as we proceed.

* * * * *

All living things possess three general properties which seem to be
unique; these are a peculiar chemical constitution, the power of repairing
themselves as their tissues wear out, and the ability to grow and
multiply. The third property is so familiar that we fail to see how
sharply it distinguishes the creatures of the organic world. To realize
this we have only to imagine how strange it would seem if locomotives and
steamships detached small portions of themselves which could grow into the
full forms of the parent mechanisms. Equally distinctive is the marvelous
natural power which enables an animal to re-build its tissues as they are
continually used up in the processes of living; for no man-made,
self-sustaining mechanism has ever been perfected. The property of chemical
composition is believed by science to be the basis of the second and the
third; but this matter of chemical constitution must take its proper place
in the series of structural characters, which we shall discuss further on
as we develop the conception of organic mechanism.

Whatever definition we may employ for a machine or an engine, we cannot
exclude the living organism from its scope. As a "device for transforming
and utilizing energy" the living organism differs not at all from any
"dead" machine, however complex or simple.