up by Mother Nature there is placed along
with the fuel for burning a tiny bit of material to be used for repair
of the machine. In other words, food represents in its composition both
the coal and the metal repair materials of the locomotive. The starch,
sugar and fat of foods are the coal and the protein or albumin is the
metal repair stuff. Here we see at once the reason why starch and sugar
and fat are so abundant in our foodstuffs, while protein or albumin is
in quantity a minor element.

But there are other differences between food and common fuel which are
worthy of mention. The water and the salts are essential to meet the
body's needs, especially the various mineral elements, lime, soda,
potash and iron. All these we must have--lime for the bones and nerves,
soda and potash to neutralize the harmful acid products of combustion
processes, and iron for the blood.

All these are found in normal foodstuffs, but in greatly varying
proportions, so that a pretty large variety of foods must be eaten to
make sure that each of the different food principles required for
perfect nutrition are supplied in ample quantity.

In recent years science has discovered another and most surprising
property of food in which it transcends all other fuel substances as a
diamond from the Transvaal outshines a lump of coal. Natural food
contains vitamines. It has long been known that an exclusive rice diet
sometimes causes beri-beri, a form of general neuritis, and that a diet
of dry cereals and preserved food in time gives rise to scurvy, but the
reason was a profound mystery. In very recent years it has been learned
that the real cause of beri-beri and scurvy is the lack of vitamines
which are associated with the bran of cereals and so are removed in the
process of polishing rice and in the bolting of wheat and other grains.

Vitamines do not enter into the composition of the body as do other food
principles, but they are somehow necessary to activate or render active
the various subtle elements which are essential to good nutrition.

There are several kinds of vitamines. Some are associated with the bran
of cereals, other with the juices of fruits. Some are easily destroyed
by heat, while others survive a boiling temperature. The discovery of
vitamines must stand as one of the most masterly achievements of modern
science, even outshining in brilliancy the discovery of radium. It was
only by the most persevering efforts and the appl