Rohrer [1924], using the Krogh microrespirometer, found that the feeding of thyroid hormone to mice caused an increase in the O2 consumption of liver, kidney and muscle tissue. Foster [1926] observed that thyroidectomy produced a diminished O2 uptake of muscle tissue respiring in glucose, a result also reported by Dye & Maughan [1929a, b] with and without the addition of succinate to the respiring muscle mince. Many workers have reported increases in O2 uptake of surviving tissues after treating animals with thyroxine or thyroid preparations; notably Dresel [1928] in kidney and liver, Anselmino, Eichler & Schlossmann [1929] in liver, spleen and kidney, Hopping [1930] in alligator red blood cells, Hicks [1932] in muscle, McEachern [1932] in heart, Dye [1933] in muscle, Gerard & McIntyre [1933] in liver, auricle and vagus nerve, Meyer, McTiernan & Aub [1933] in liver, Ebina [1932] in liver and kidney, McEachern [1935]