It is a fact of great interest that when 131I-thyroxine and 131I-triiodothyronine are exogenously given, they are highly concentrated in the anterior hypothalamus, median eminence, and hypophysis. Schittenhelm and Eisler (1932) already found that the intravenous injection of 1.0mg/kg of thyroxine (T4) into dogs, cats and rabbits elevated iodine concentration in the tuber cinereum 10times. Since...