Twenty-six animals were operated upon for the production of jejunal ulcers using a slight modification of the technic of Mann and Williamson1 for depriving the jejunum of its normal alkalinity.In each case the duodenum was transected between the pylorus and the ampulla of Vater and both ends inverted with silk. The jejunum was then divided a few inches beyond Treitz's ligament and again both ends inverted. Following this a gastro-enterostomy was performed between the distal end of the jejunum and the stomach and an enteroenterostomy performed between the closed duodenojejunal loop and the upper ileum about 24 inches below the gastroenterostomy, allowing the bile, pancreatic juice and duodenal secretions to be emptied back into the small bowel at this point. These changes were made in the original procedure because it was felt that the nutrition of the animals would be better preserved if the drainage were done higher in the small intestine, thereby eliminating this factor from the ultimate results. Also s...