Copy letter from Maurice M Rapport, Sloan-Kettering Institute, 444 East 68th Street, New York 21, New York, to Dr J H Gaddum, Department of Pharmacology, University New Buildings, Teviot Place, Edinburgh Discusses the 'very complex pharmacology of serotonin'. The Upjohn Company have synthesized 5- hydroxytryptamine and will publish on it shortly. Comments on the difficulty of preparing it, but will sent Gaddum a sample within days. Discusses its effects as pressor and depresssor in various animal tests. Relates Professor Gilman's thinking on serotonin. Rapport sketches the structures of histamine and serotonin and notes his intention to work on their relationship in Bovet's laboratory. 14 September 1951