plasm, it simply gives rise to
heat?
One of the primary questions to demand attention in this search is
whether we are to find the explanation, at the bottom, a _chemical_ or a
_mechanical_ one. In the simplest form of life in which vital
manifestations are found are we to attribute these properties simply to
chemical forces of the living substance, or must we here too attribute
them to the action of a complicated machinery? This question is more
than a formal one. That it is one of most profound significance will
appear from the following considerations:
Chemical affinity is a well recognized force. Under the action of this
force chemical compounds are produced and different compounds formed
under different conditions. The properties of the different compounds
differ with their composition, and the more complex are the compounds
the more varied their properties. Now it might be assumed as an
hypothesis that there could be a chemical compound so complex as to
possess, among other properties, that of causing the oxidation of food
to occur in such a way as to produce assimilation and growth. Such a
compound would, of course, be alive, and it would be just as true that
its power of assimilating food would be one of its physical properties
as it is that freezing is a physical property of water. If such an
hypothesis should prove to be the true one, then the problem of
explaining life would be a chemical one, for all vital properties would
be reducible to the properties of a chemical compound. It would then
only be necessary to show how such a compound came into existence and we
should have explained life. Nor would this be a hopeless task. We are
well acquainted with forces adequate to the formation of chemical
compounds. If the force of chemical affinity is adequate under certain
conditions to form some compounds, it is easy to conceive it as a
possibility under other conditions to produce this chemical living
substance. Our search would need then to be for a set of conditions
under which our living compound could have been produced by the known
forces of chemical affinity.
But suppose, on the other hand, that we find this simplest bit of living
matter is not a chemical compound, but is in itself a complicated
machine. Suppose that, after reducing this vital substance to its
simplest type, we find that the substance with which we are dealing not
only has complex chemical structure, but that it also possesses a large
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