certain directions.
These fundamental properties are then the properties of the cell
_machine_ just as surely as printing is the property of the printing
press. We can no more account for the life phenomena by chemical powers
than we can for printing by chemical forces manifested in the burning of
the coal in the engine room. To be sure, it is the chemical forces in
the engine room that furnishes the energy, but it is the machinery of
the press that explains the printing. So, while chemical forces supply
life energy, it is the cell machinery that must explain the fundamental
living factors. So long as this machine is intact it can continue to run
and perform its duties. But it is a very delicate machine and is easily
broken. When it is broken its activities cease. A broken machine can not
run. It is dead. In short, we come back once more to the idea of the
machinery of protoplasm, and must base our understanding of its
properties upon its structure.

It is proper to state that there are still some biologists who insist
that the ultimate explanation of protoplasm is purely chemical and that
life phenomena may be manifested in mixtures of compounds that are
purely physical mixtures and not machines. It is claimed that much of
this cell structure described above is due to imperfection in
microscopic methods and does not really exist in living protoplasm,
while the marvellous activities described are found only in the highly
organized cell, but do not belong to simple protoplasm. It is claimed
that simple protoplasm consists of a physical mixture of two different
compounds which form a foam when thus mixed, and that much of the
described structure of protoplasm is only the appearance of this foam.
This conception is certainly not the prevalent one to-day; and even if
it should be the proper one, it would still leave the cell as an
extremely complicated machine. Under any view the cell is a mechanism
and must be resolved into subordinate parts. It may be uncertain whether
these subordinate parts are to be regarded simply as chemical compounds
physically mixed, or as smaller units each of which is a smaller
mechanism. At all events, at the present time we know of no such simple
protoplasm capable of living activities apart from machinery, and the
problem of explaining life, even in the simplest form known, remains the
problem of explaining a mechanism.

==The Origin of the Cell Machine.==--We have thus set before us another