should call them the "unidentified dietary factors" and added later to
this phrase, the terms water-soluble "B" and fat-soluble "A" after the fat
soluble form was discovered. Most chemists feel, however, that the purpose
of nomenclature is brevity combined with ready recognition of what you are
discussing and that it is unnecessary to change the name vitamine until we
know exactly what the substances are. The result is that while still a
mystery chemically they remain under the name of vitamine and the kinds
are distinguished by the McCollum terms "fat-soluble" A, "water-soluble"
B, and "C."

We see that beri-beri then was responsible for Funk's adding to our
chemical entities a new member but it does not yet appear why this entity
concerns our normal nutrition. To get this relation we must turn for a
moment to the state of knowledge in 1911 in regard to foods and their
evaluation and what was going on in this field of study at the time.

A great advance in measuring food value was the discovery of the
isodynamic law. Translated into ordinary language this law states that
when a person eats a given amount of a given kind of food, that food may
liberate in the body practically the same amount of energy that it would
produce if it were burned in oxygen outside of the body. The confirmation
of this law permitted us to apply to the measurement of food the same
method we had already learned to use in measuring coal. For convenience
the physicists devised a heat measure unit for this purpose and naturally
called it by a word that means heat, namely, "calorie." Using this unit
and applying the isodynamic law it was merely necessary to determine two
things; first, how many calories a man produces in any given kind of work,
second how many calories a given weight of each kind of food will yield,
and then give the man as many calories of food as he needs to meet his
requirements when engaged in a given kind of labor. The measurement and