Ligation of the cardiac end of the stomach or of the esophagus in ten dogs produced a severe toxemia, and rapid death. In seven of the animals there occurred a marked rise in the total non-protein nitrogen and urea nitrogen of the blood. The dogs living longest with cardiac obstruction showed a fall in blood chlorides and a rise in the CO2-combining power of the plasma. All the dogs with an obstruction of the esophagus showed a fall in blood chlorides. Control animals subjected to other types of abdominal operations showed no significant changes in the blood.