THAT emotional stress may be the occasion for a fall in the rate of urine-secretion, even to the degree of total suppression, has been recognised since the reference by Bernard [1859] to certain cases of vesico-vaginal fistula operated upon by Jobert and in which "par suite de l'emotion, l'ecoulement de l'urine avait ete suspendu pendant toute la duree de l'operation, et quelquefois meme bien au dela." Bernard makes this reference in connection with the darkening of the blood in the renal veins which he observed to accompany the inhibition of urine-flow during severe abdominal operations on the dog and rabbit: the suggestion is implicit, therefore, that the inhibition following emotional stress has likewise a vasomotor cause. The fact, however, that an effective stress may be of apparently small degree [Mackeith, Pembrey, Spurrel, Warner, and Westlake, 1923;Theobald, 1934] and the consideration that a reduced blood-flow through the kidney forms, on teleological grounds, an unattractive accompaniment, have been partly responsible for recent attempts to discover the incidents of the phenomenon of inhibition and to disclose their accidental or essential relation with it. The demonstration of the persistence of the phenomenon in the dog after section of the renal nerves, and indeed of all organic connection between the animal and its kidney [Theobald and Verney, 1935], has now excluded these nerves from functional participation, and in so doing has testified to intervention through humoral channels. Reasons, moreover, have been advanced [Theobald and Verney, 1935] against this intervention's being in the nature of a change in the partition of water between blood and tissues: a humorally transmitted agent has therefore been postulated, and its identity with adrenaline made unlikely by the dissimilarity between the course of inhibition due to emotion and that due to an intravenous injection of this drug.The view that the agent is identical with the antidiuretic substance of post-pituitary extract, however [Theobald and Verney, 1935], is supported on the one hand by the superficial resemblance of the courses of inhibition from emotional stress and the intravenous 1 Fellow of the Rockefeller Foundation.