1. The modified Meyer method here proposed, of parallel tests upon segments of surviving carotid and coronary arteries from the ox, is a satisfactory means for detecting epinephrin in complex body fluids like blood.
2. At the present time there is no evidence that epinephrin, in amounts sufficient to produce its physiological effects upon any hitherto used test objects, exists in the circulating blood, with the exception of blood from the suprarenal vein.
3. The examination of uncoagulated blood from six persons with high blood pressure has failed to show the presence of epinephrin or other constricting substances.
4. The constrictor substance in defibrinated blood and serum is not an epinephrin-like substance. In its point of action and its effects it is similar to barium chlorid. It is a direct stimulant to smooth muscle and seems to have no relation to the sympathetic innervation of muscle.