mentality the comparison of the body with a
machine fails of being complete.

In regard to the second half of the question, whether natural forces are
adequate to explain the running of the machine, we have again been able
to reach a satisfactory positive answer. Digestion, assimilation,
circulation, respiration, excretion, the principal categories of
physiological action, and at least certain phases of the action of the
nervous system are readily understood as controlled by the action of
chemical and physical forces. In the accomplishment of these actions
there is no need for the supposition of any force other than those
which are at our command in the scientific laboratory.

==The Living Machine Constructive as well as Destructive.==--In one
respect the living machine differs from all others. The action of all
other machines results in the _destruction_ of organized material, and
thus in a _degradation of matter_. For example, a steam engine receives
coal, a substance of high chemical composition, and breaks it into _more
simple_ compounds, in this way liberating its stored energy. Now if we
examine all forms of artificial machines, we find in the same way that
there is always a destruction of compounds of high chemical composition.
In such machines it is common to start with heat as a source of energy,
and this heat is always produced by the breaking of chemical compounds
to pieces. In all chemical processes going on in the chemist's
laboratory there is similarly a destruction of organic compounds. It is
true that the chemist sometimes makes complex compounds out of simpler
ones; but in order to do this he is obliged to use heat to bring about
the combination, and this heat is obtained from the destruction of a
much larger quantity of high compounds than he manufactures. The total
result is therefore _destruction_ rather than manufacture of high
compounds. Thus it is a fact, that in all artificial machines and in all
artificial chemical processes there is, as a total result, a degradation
of matter toward the simpler from the more complex compounds.

As a result of the action of the living machine, however, we have the
opposite process of _construction_ going on. All high chemical compounds
are to be traced to living beings as their source. When green plants
grow in sunlight they take simple compounds and combine them together
to form more complex ones in such a way that the total result is an
increase of chemical