1. In order to study the ability of the ileum of the sheep to digest and absorb protein, casein or gluten were infused into the intestine of rams through cannulas inserted at distances of 0·05, 7, 9 and 15 m from the pylorus. Amounts of casein or gluten containing 10–20 g nitrogen were infused during 24 h, in animals given a low-N diet.
2. N balance was negative during the preliminary period when no infusion was given; infusion of casein or gluten increased the daily N retention to 5–15 g.
3. Infusion of proteins into the intestine did not induce an increased activity of pancreatic proteases in digesta withdrawn from the lower part of the intestine.
4. The increased N retention after the infusion of proteins into the lower part of the intestine indicates a considerable capacity of this section of the intestine to digest and absorb proteins.