Methods. The animals were in all cases anesthetised, generally with morphia and ACE mixture. In a few cases the morphia was omitted, but in these cases the gut was not found to be more active than in the others. In all cases the muscular wall of the gut was cut through at the level of the attachment of the levator ani, in order to avoid the shifting of the whole gut into the pelvis which is produced by contraction of the recto-coccygeal muscles. A dose of castor oil was administered the day before the experiment. In most cases the small intestine was also cut through just above the ileocaecal valve, and the whole colon washed through with normal salt solution. The balloon which was connected with the recording tambourwas introduced into the gut through the lower opening, or through the ileocaecal valve, or more rarelythrough a small incision in the wall of the gut. The separation of the gut from the central nervous system was