The Vitamine Manual | Page 7

oil, lard, or
vegetable oils of various sorts. Carrying out the lead here suggested he
tried egg yolk fats. They proved as effective as butter fat.
[Illustration: FIG. 1. COMPOSITE CHART OF MCCOLLUM AND
DAVIS PUBLICATIONS
I (from _Journ. Biol. Chem._, 1913, xv, 167). This chart shows the
effect in period III of the addition of an ether extract of egg, 1 gram
being given every other day. The diets for periods I-IV were as follows:
Periods . . . . . . . . . . . . . . . I II III IV Salt mixture . . . . . . . . . . . . 6 6 6 6
Casein . . . . . . . . . . . . . . . 18 18 18 18 Lactose . . . . . . . . . . . . . . . 20 0
0 0 Dextrin . . . . . . . . . . . . . . . 0 59 74 74 Starch . . . . . . . . . . . . . . . 31
0 0 0 Agar-agar . . . . . . . . . . . . . . 5 2 2 2 Egg (see above) . . . . . . . . . . .
0 0 * 0 *1 gram extract every other day
II and III (from _Journ. Biol. Chem._, 1915, xxiii, 231). These charts
show the effect (II) of the addition of as little as 2 per cent wheat
embryo as sufficient to secure normal growth when it serves as a
supply of the B vitamine. Chart III shows that even when the wheat
embryo is increased to 30 per cent it is inadequate for growth unless the
A is also present. The diets were as follows:
Dextrin . . . . . . . . 69.3 52.8 Salt mixture . . . . . . 3.7 2.6 Butter
fat . . . . . . . 5.0 0.0 Agar-agar . . . . . . . 2.0 2.0 Casein . . . . . . . . . 18.0
12.6 Wheat embryo . . . . . . 2.0 30.0]
These results linked up with those of Stepp and Mendel and showed
that butter fat and egg yolk fat contained a growth factor which was

missing in other fats. McCollum named this the "unidentified dietary
factor fat- soluble A."
In the same year F. G. Hopkins in England announced that the addition
of 4 per cent of milk to diets consisting of purified nutrients would
convert them into growth producers. This was too small an amount to
admit of attributing the cause to milk proteins, fats, carbohydrates, or
salts. Hopkins therefore suggested the existence of unknown factors in
milk of the type to which he had earlier given the name "accessory
factors." This work has recently been repeated by Osborne and Mendel
who fail to find the high potency in milk ascribed to it by Hopkins but
the latter's work, at that time, was accepted without question and
became the impetus to important discoveries.
Mendel and Osborne had meanwhile investigated more in detail their
milk fractions. They obtained results that confirmed McCollum's
findings for butter fat but in addition they showed that by removing all
the fat and protein from milk they obtained a residue which played an
important part in growth stimulation and that this factor was different
from the salts present in the mixture. This specially prepared milk
residue they called protein-free milk.
The next few years are a melting pot of investigations. They included
some sharp controversies over nomenclature and many apparently
contradictory conclusions based on what we now know to be
insufficient data. The principal outcome was the identification of the
yeast and rice polishing substance with the factor carried by
protein-free milk. On the basis of these results Funk put forward the
idea that McCollum's butter-fat and egg-yolk factor was merely
vitamine which clung to the fats as an adulterant. It was soon shown,
however, that butter fat could be obtained that was absolutely free of
nitrogen and still be stimulatory to growth. It was therefore clear that
whatever the factor present it could not be the Funk vitamine. From out
of the smoke of this controversy came an ultimate explanation that was
very simple. There were two factors instead of one. McCollum did not
discover the presence of the Funk vitamine in his mixtures at first
because it was carried by the lactose and he did not know it. Finally, to

cut a long story very short, these two factors or vitamines were both
found to be essential to growth and in the feeding mixtures that had
been used were