rings, connecting rods, etc. Separate tests of each part may
show that it functions perfectly when working alone. But in
addition to the separate parts there are many interconnecting
elements. The parts cannot work well unless the bearing sur-
faces have just the right amount of play, the magneto must
give the spark at the precise instant of greatest compression, the
oiling system and pump system must be properly connected with
some part moved by the crankshaft. Unless all of the parts
are properly interconnected and timed the engine as a whole
will not perform its function, that is, turn the propeller.

When we speak of the action of the individual as a whole,
we mean something of this nature. It must be borne in mind
that the human being has not one function to perform but thou-
sands, and the adjustments of the parts must vary in each and
every new duty if the work of the whole organism is to be
efficient. Only a well constructed biological organism properly
trained can meet these requirements. No mechanical contrivance
yet hit upon approaches the human organism in its multiplicity
of possible functions and in the rapidity with which co-ordina-
tions of separate functions can be so rapidly shifted for each
new duty of the machine as a whole.

It is interesting to push our possible analogy one step further.
If we know enough about the parts of any mechanical contrivance,
the nature of the interlocking systems and the various inter-
dependent functions, we can make safe predictions about how
it will work under new conditions or specify the changes which
will have to be made if the contrivance must perform some new
function. For example, in the case of our engine, we know it
is good for high speed and short runs. Such and such changes
will have to be made if it is to be used for medium duty or
forced to pull heavy loads. We know further that with the
oiling and cooling systems as they now are it will not run in a
very cold climate; with the fuel system now employed it cannot
be used where oxygen tension is low; that heavy fuel such as kero-
sene or crude oil will not burn in it; that it will run in fresh water
indefinitely but that certain parts will have to be made of bronze
if it is to run smoothly in sea water for any length of time.

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