1. The nerve cord of the lobster (Homarus americanus Milne-Edwards) is very delicate and can be used as a living preparation for only a few hours after its removal from the animal.
2. During the first hour or so after removal it discharges CO2 at a steadily decreasing rate beginning at about 0.20 mg. CO2 per gram of cord per minute and ending at about 0.07 mg.
3. This discharge exhibits a steady decrease in rate and is not divisible into a period of gush and a period of uniform outflow as with the lateral-line nerve of the dogfish. It terminates in a very few hours with the complete death of the cord.
4. Both handling and cutting the cord temporarily increase the rate of CO2 output.
5. The stimulated cord discharges CO2 at a rate about 26 per cent higher than that of the quiescent cord, an increase of about 1.6 times that of the increase observed in the lateral-line nerve of the dogfish under similar circumstances.
