depression of heat production. The drop in body temperature of the restrained rat, in fact, appears to be the cause of the drop in oxygen consumption (metabolism), for if the reverse were true the 1l3l uptake (thyroid metabolism) should have been higher in the nonrestrained than in the restrained animals.Summary. Thyroid 11'3f uptake by restrained rats was higher at one hour, and lower at 4 hours, than that of nonrestrained control animals. The lower the body temperature of the restrained animals at 4 hours, the lower the IZz3l uptake by the thyroid. Restrained hypothermic rats had a significantly greater thyroid uptake of than equally hypothermic nonrestrained animals. It is concluded that hypothermia of restrained animals can not be ascribed to depressed basal metabolism.