1. Severe and sufficient non-fatal injury to the suprarenal cortex by freezing or by ligation in cats causes a significant and prolonged increase in heat production.
2. Lethal injury to the suprarenals by freezing, ligation, or partial excision in cats causes a fall in heat production.
3. Insufficient injury to the suprarenals by freezing, ligation, or partial excision in cats produces no significant alteration in heat production.
4. Further evidence of a dose thyroid-suprarenal cortex interrelationship is indicated by the rapidity of thyroid hyperplasia and by the effects of KI after suprarenal crippling.