Abstract
That butter fat and egg yolk fats contain a substance whose chemical nature is unknown, which is indispensable for growth or prolonged maintenance of health was first pointed out by McCollum and Davis. Later they showed the presence of this substance in the maize kernel and in wheat embryo, and presented some evidence that if it is found in the oat kernel it is in very small amount. 2 Our further studies have confirmed these observations.
McCollum and Kennedy 3 have discussed the desirability of employing the term “fat-soluble A” for this, to distinguish it from the “water-soluble B,” a substance which is widely distributed in the natural foodstuffs of both animal and vegetable origin and is likewise indispensable for growth or prolonged maintenance. The water-soluble B only is concerned with the production and cure of polyneuritis in pigeons.
Our experimental work with the grains has shown that the content of the fat-soluble A is greater in the maize kernel than in wheat, and greater in wheat than in the oat kernel. In all three the content is too low to induce growth at the maximum rate even though all other factors in the diet be near the optimum.
We have much experimental evidence indicating that the unknown A is principally confined to the germ of the seed. Sunflower seed appears to be fairly rich in this substance.
We have also found that the leaves of certain plants, especially alfalfa and cabbage are very rich in the fat-soluble A as compared with the grains. It is probable therefore that it is universally associated with metabolizing plant cells. We have rats in our colony which have grown to very near the normal adult size at slightly below the normal rate on a simple mixture of polished rice sixty and powdered alfalfa leaves forty per cent.
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