THE EFFECT OF THERMAL ENVIRONMENT ON THE MORPHOLOGY OF THE THYROID AND ADRENAL CORTICAL GLANDS IN THE ALBINO RAT1

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Abstract
By means of weighed paper reconstructions, thyroid (epithelial cell height) and adrenal cortical (distr. of cortical sudanophilic substance) indices were detd. in a series of 150 albino rats (60-90 days of age) autopsied during various mos. of the yr. Animals autopsied during winter mos. consistently demonstrated a high thyroid and a low adrenal index. Summer animals demonstrated a converse situation. These variations could not be correlated with normal laboratory temps. The adrenal cortex, in contradistinction to the thyroid, was apparently more readily affected by changes in temp. which could be considered normal. These results were compared with those produced in a series of 120 animals, groups of which were exposed to a wide variety of experimentally altered environmental temps. In general, the inverse relation between the thyroid and the adrenal cortex was maintained. Increased environmental temps. resulted in lowered thyroid and increased adrenal indices, whereas diminished temps. resulted in the converse. These effects were reversible provided no tissue injury had been sustained and no specific effects, other than those brought about by changes in general body temp., could be attributed to any exptl. thermogenic agent employed. A relation between body temp. and the thyroid-adrenal cortical apparatus is suggested which may function as an accessory to the neural thermoregulating mechanisms.