1. The thyroid exerts a retarding action on the carbohydrate destroying mechanism of the body. 2. This retarding action is not changed when the gland is boiled, showing that it is not a ferment action. 3. Iodothyrin, the active principle of the gland, exerts this retarding influence more markedly even than the whole thyroid. 4. This antagonism between the thyroid and the carbohydrate destroying mechanism is a direct one, as other ductless glands and the nervous system are eliminated from the experiments. 5. These results confirm those of Falta along similar lines.