Letter from Henry Dale, National Institute of Medical Research, Hampstead to Howard Walter Florey Has no doubt that the nervous system is involved in, and is chiefly responsible for, many of the conditions which are called "shock" - discusses the definition of "shock" - comments on "primary shock" and on factors involved in the production of "secondary shock" -comments on case described by McMichael in which patient's circulation failed through accumulation of fluid in tissues of legs - comments on his attempts, with Laidlaw and Richards, during last war, to analyse the shock produced by histamine - absurd to talk of "the" cause of shock - should recognise shock as a symptom, or syndrome, and concentrate attention on its treatment. 29 October 1940