ZINC AS A NORMAL CONSTITUENT OF FOODS

Less than a quarter of a century ago, iodin assumed a new physiologic significance through the discovery of its constant presence in the body as a constituent of the thyroid gland. Compared with such elements as calcium or chlorin or iron, the quantity of iodin occurring in the organism is exceedingly minute. In contrast with the hundreds of grams of lime, for example, a few milligrams of iodin represent the entire complement of the latter constituent; nevertheless it has already established a claim for indispensability in the normal functioning of the body. Indeed, there are few more striking illustrations of the profound potency of minute portions of any element than are afforded by the iodin-containing thyroxin which Kendall has succeeded in isolating from the thyroid gland.

This experience with iodin has paved the way for a more respectful attitude toward suggestions of the possible physiologic rôle of other elements which