nd, nor have we any idea
in what direction to look. But the fact that nature has methods of
machine building, as we have seen, may hold out the possibility that
some day we may discover her method of building this primitive living
machine, the cell.

It is useless to try to go further at present. The origin of living
matter is shrouded in as great obscurity as ever. We must admit that the
disclosures of the modern microscope have complicated rather than
simplified this problem. While a few years ago chemists and biologists
were eagerly expecting to discover a method of manufacturing a bit of
living matter by artificial means, that hope has now been practically
abandoned. The task is apparently hopeless. We can manipulate chemical
forces and produce an endless series of chemical compounds. But we can
not manipulate the minute bits of matter which make up the living
machine. Since living matter is made of the adjustment of these
microscopic parts of matter, we can not hope to make a bit of living
matter until we find some way of making these little parts and adjusting
them together. Most students of protoplasm have therefore abandoned all
expectation of making even the simplest living thing. We are apparently
as far from the real goal of a natural explanation of life as we were
before the discovery of protoplasm.

==General Summary.==--It is now desirable to close this discussion of
seemingly somewhat unconnected topics by bringing them together in a
brief summary. This will enable us to see more clearly the position in
which science stands to-day upon this matter of the natural explanation
of living phenomena, and to picture to ourselves more concisely our
knowledge of the living machine.

The problem we have set before us is to find out to what extent it is
possible to account for vital phenomena by the application of ordinary
natural laws and forces, and therefore to find out whether it is
necessary to assume that there are forces needed to explain life which
are different from those found in other realms of nature, or whether
vital forces are all correlated with physical forces. It has been
evident at a glance that the living body is a machine. Like other
machines it consists of parts adjusted to each other for the
accomplishment of definite ends, and its action depends upon the
adjustment of its parts. Like other machines, it neither creates nor
destroys energy, but simply converts the potential energy of its food