These experiments indicate the existence of an inhibitory central mechanism, located in the region of the brain bounded by the superior colliculi and the optic chiasm, which influences epinephrine secretion from the adrenal glands. The existence of a central mechanism in the spinal cord, which exercises an opposite influence to that of this cerebral centre, was established earlier.2 Removal of the influence of the brain centre, results in epinephrine output from the adrenals at the maximum rate of spontaneous liberation which can be sustained through the physiological activity of the spinal cord centre. This rate corresponds with the upper limit of the range of normal epinephrine secretion.1