1. The crayfish stomatogastric ganglion (SG) contains about twenty-five neurone somata; it supplies motor innervation for the anterior gut, and receives afferent input from mechanoreceptors associated with the stomach. Its proximal branches respond to normal stomach contractions with a complex, patterned, centrally directed discharge involving several units.
2. Discharges from the largest of these can be recorded nearly simultaneously in the two superior oesophageal (proximal) and the two lateral (distal) nerves from SG. In preparations with these lateral nerves connected to the stomach the cell shows constant-frequency spontaneous activity, which can be reset by direct stimulation of any one of the four branches. Mechanical stimulation of the cardiac ossicles evokes a burst discharge.
3. Simultaneous recording from the two lateral nerves shows that impulses in one of them consistently occur earlier; this temporal relationship is preserved when the leading side is stimulated, but reverses (usually accompanied by polarity changes) when the other is stimulated. Each lateral branch continues to respond independently after being cut at its point of entry into SG.
4. It is concluded that the cell is a new type of receptor neurone, with a bifurcating axon and two dendrites, each autogenically active at its receptor terminal. The higher-frequency input always determines the output rhythm. A cell with the appropriate configuration was figured by Orlov (1927) from methylene blue-stained SG preparations.