The case here described seems to be of sufficient interest and rarity to justify publication. The patient, a man aged 44, was brought into hospital eight hours after the sudden onset of severe pain all over the abdomen. Before admission he had vomited two or three times. He had been suffering from indigestion for the previous few months, that is, he had intermittent abdominal pain after food, relieved by vomiting. On examination he was grey and anxious. The whole abdomen was rigid and liver dullness on percussion seemed to be diminished. His pulse rate was 160, his blood pressure 120/180. A provisional diagnosis of perforated peptic ulcer was made, although the repeated vomiting and shock were against the diagnosis. On opening the abdomen the peritoneal cavity was found to contain dark brown fluid. The transverse colon was dilated and its contents looked dark and more than usually fluid. The transverse mesocolon was oedematous and thickened. The stomach and duodenum were normal and no other abnormality wa...