r bodies by the
processes of digestion and assimilation release the captured energy
which warms us with heat brought from the sun and shines out in human
thought and action.

It is less than a century since Liebig and Lehmann and their pupils
began to unravel the mystery of food. In recent years no subject has
received more assiduous attention from scientific men, and none has been
made the object of more constant or more profound research than the
questions of food and food supply. The feeding of animals and men is
without question the most pressing and vital of all economic problems.

The labors of Voit and Pettenkofer, Rubner, Zuntz, Atwater, Benedict,
Chittenden, Mendel, Lusk and Hindhede have demonstrated that there is
the closest relation between food supply or food selection and human
efficiency. In fact, it has been clearly shown that the quality of the
food intake is just as directly and as closely related to the question
of human efficiency as is the quality and quantity of gasoline to the
efficiency of an automobile.

In fact it has been established as a fundamental principle in human
physiology that food is fuel. Life is a combustion process.

The human body is a machine which may be likened to a locomotive--it is
a self-controlling, self-supporting, self-repairing mechanism. As the
locomotive rushes along the iron road, pulling after it a thousand-ton
cargo of produce or manufactured wares or human freight sufficient to
start a town or stock a political convention its enormous expenditure of
energy is maintained by the burning of coal from the tender which is
replenished at every stopping place. The snorting-monster at the head of
the rushing procession gets hungry and has to have a lunch every few
miles along the way. After a run of a hundred miles or so the engine
leaves the train and goes into a roundhouse for repairs; an iron belt
has dropped out or a brass nut has been shaken off. Every lost or
damaged part of the metal leviathan is replaced, and then it is ready
for another century run.

The human body is wonderfully like the locomotive. It pulls or carries
loads, it expends energy, it consumes fuel and has to stop at meal
stations to coal up; it has to go off duty periodically for repairs. The
body needs just what the locomotive needs--fuel to furnish energy and
material for repair of the machinery.

Food differs from fuel chiefly in the one particular, that in each
little packet of food done