Metabolism of L-Thyroxine and L-3:5:3′-Triiodothyronine by Brain Tissue Preparations11This investigation was supported in part by a research grant (C-2052) from the National Institutes of Health, Public Health Service. It was also supported in part by a grant-in-aid from the American Cancer Society upon recommendation of the Committee on Growth of the National Research Council. This work was undertaken during the tenure of a Damon Runyon Memorial Fund Grant. This work was also made possible by support from the United States Atomic Energy Commission under their contract No. AT (30–1)-910.