It was in 1891 that Jacobi[29] described nerve fibres derived from the splanchnic trunks which were distributed to the adrenal glands. Six years later Biedl[30] found that these nerves conveyed vasodilator impulses to the glands, and he suggested that they probably conveyed also secretory impulses. Evidence in support of this suggestion was presented the following year by Dreyer,[31] who demonstrated that electrical excitation of the splanchnic nerves produced in the blood taken from the adrenal veins an increased amount of a substance having the power of raising arterial blood pressure, and that this result was independent of accompanying changes in the blood supply to the glands. The conclusion drawn by Dreyer that this substance was adrenin has been confirmed in various ways by later observers. Tscheboksaroff[32] repeated Dreyer’s procedure and found in blood taken from the veins after splanchnic stimulation evidences of the presence of adrenin that were previously absent. Asher[33] observed a rise of blood pressure when the glands were stimulated in such a manner as not to cause constriction of the arteries--the rise was therefore assumed to be due to secreted adrenin. Dilation of the pupil was used by Meltzer and Joseph[34] to prove secretory action of the splanchnics on the adrenal glands; they found that stimulation of the distal portion of the cut splanchnic nerve caused the pupil to enlarge--an effect characteristic of adrenin circulating in the blood. Elliott[35] repeated this procedure, but made it a more rigorous proof of internal secretion of the adrenals by noting that the effect failed to appear if the gland on the stimulated side was removed. Additional proof was brought by myself and Lyman[36] when we found that the typical drop in arterial pressure produced in cats by injecting small amounts of adrenin could be exactly reproduced by stimulating the splanchnic nerves after the abdominal blood vessels, which contract when these nerves are excited, were tied so that no changes in them could occur to influence the rest of the circulation.