METHODS Seven different types of smooth muscle preparations were used in these experiments. They were prepared from animals of either sex, stunned and bled. The guinea-pig stomach was removed from the animals with the oesophagus, thoracic vagus nerves and coeliac axis intact and attached. The vagi were dissected from the oesophagus, which was then tied off and removed. The branches of the coeliac axis running to the stomach were cleaned and prepared for perivascular nerve stimulation. The pylorus was cannulated, and the contents of the stomach were washed out with saline. The stomach was thenfilled with 25 ml. saline and set up in a 100ml. organ bath. Internal pressure changes were measured by a water manometer as described by Paton & Vane (1963). The vagus nerves and perivascular nerves were drawn through shielded platinum ring electrodes and stimulated separately. The possibility of current spread was tested, with maximal stimulator output (150 V or five times the usual stimulation voltage), by placing the