1. The infusion into the rumen via a cannula of 11. of aqueous solutions containing formic acid and/or histamine had no influence on the time sheep took to eat their food offered immediately after the infusion.

2. The infusion of formic acid solutions containing histamine into the rumen via stomach tube had variable effects when the length of stomach tube introduced was random. When they were introduced through 72 cm of stomach tube (measured from the incisor teeth), so that the end of the tube was at the cardia, one sheep consistently refused food or ate only a little but another sheep was only occasionally affected in this way.

3. Solutions marked with phenol red passed rapidly to the abomasum when introduced into the region of the cardia via a stomach tube. Only insignificant quantities of phenol red were detected within the same time in the abomasum when the solution was introduced into the rumen via a rumen cannula.