THE EFFECT OF IODINE AND IODOTHYRIN ON THE LARVÆ OF SALAMANDERS. III. THE RÔLE OF THE IODINE IN THE SPECIFIC ACTION OF THE THYROID HORMONE AS TESTED IN THE METAMORPHOSIS OF THE AXOLOTL LARVÆ

Abstract

1. Iodothyrin and inorganic iodine, in known quantities, were administered to so-called axolotl larvæ of the salamander Ambystoma tigrinum. 2. A dosis of iodothyrin containing only 0.03 mgm. iodine per 1,000 c.c. of water caused metamorphosis 13 days after its first administration. 3. A dosis of inorganic iodine 33 to 86 times larger and feeding still larger doses directly per mouth did not cause metamorphosis. 4. The amphibian metamorphosis is truly the expression of the thyroid activity and not the result of the effect of inorganic iodine. 5. Inorganic iodine as such is not the active principle of the thyroid hormone.