One of the features of investigation in physiology within the past two years has been the extensive study of the cortex of the suprarenal gland and its secretion. Recent investigations of the suprarenal structures have changed the emphasis that was placed only a few years ago on the respective functions of the different parts of the indispensable organ. The discovery of epinephrine in the medullary portion directed marked attention to the latter as a tissue of dominating significance in the body. It would be unfair to imply that the secretion of epinephrine is not of large physiologic moment. Many of the critical adjustments in the body, particularly in emergencies, are facilitated by this aspect of suprarenal response. Nevertheless, when considered in terms of absolute indispensability for life, the cortex of the suprarenal now must take first rank. Without the medulla, existence may still be assured; not so without the cortex.