A survey of the literature on the motor function of the alimentary canal clearly reveals that, in general, oversimplified assumptions are made about the anatomy of the nerve and muscle structures involved. Electron-microscopic evidence on the myenteric plexus is relatively scanty (Richardson, 1958, 1960; Hager & Tafuri, 1959; Taxi, 1958, 1965; Baumgarten, Holstein & Owman, 1970), and has been reviewed recently (Schofield, 1968; Burnstock, 1969). All accounts have reported an extremely complex picture. Richardson (1958) demonstrated the occurrence of synaptic junctions in the intramural ganglia, and Baumgarten et al.(1970) were able to identify three types of vesiculated nerve processes and to suggest their possible neurochemical nature.

The present investigation is an attempt to identify different types of nerve fibres and interneuronal junctions. Together with experimental investigations in progress, this may lead to clarification of the complicated neural circuitry of the myenteric plexus. The classical concept of sympathetic and parasympathetic outflows running almost independently to the very periphery has been severely questioned in recent years and is giving place to a more subtle concept of integrated pathways in the gut wall itself.