1. A modified Osterhout respiratory apparatus for the detection of CO2 from nerve is described.
2. The lateral-line nerve from the dogfish discharges CO2 at first with a gush for half an hour or so and then steadily at a lower rate for several hours.
3. Simple handling of the nerve does not increase the output of CO2; cutting it revives gush.
4. The CO2 produced by nerve is not escaping simply from a reservoir but is a true nervous metabolite.
5. The rate of discharge of CO2 from a quiescent nerve varied from 0.0071 to 0.0128 mg. per gram of nerve per minute and averaged 0.0095 mg.
6. Stimulated nerve showed an increased rate of CO2 production of 15.8 percent over that of quiescent nerve.
7. The results of these studies indicate that chemical change is a factor in nerve transmission.
