Abstract
1. In accordance with the dual histology of Auerbach's plexus (Dogiel, 1899; Hill, 1927) two types of neurone can be shown to be humorally active in plexus-containing preparations of longitudinal muscle from guinea-pig ileum, taken at measured distances up to 95 cm above the ileocaecal valve, when such preparations are stimulated electrically under different conditions.