INTRODUCTION
THE STIMULUS for this study evolved in part from an unusual case of acute, massive pneumoperitoneum occurring in a child after perforation of an ileal ulcer opposite the neck of a Meckel diverticulum.1 The extreme abdominal distention with encroachment on the thorax, as shown in figure 1, was deflated by paracentesis, and yet at the time of the operation, less than one hour later, the distention had returned to its original size and the respiratory rate had increased to 45 per minute.Where did such a large volume of gas come from and how did it accumulate so quickly? The outstanding work of Wangensteen, Hibbard and Rea2 and Singleton and co-workers3 has established atmospheric air as the major source of gas in distention secondary to acute intestinal obstruction. It would seem that exogenous air must also have been the predominant source in the case cited, for