Since the advent of pneumoperitoneum, or air inserted into the abdominal cavity, as an aid in roentgen-ray diagnosis, much has been done to simplify the technic, and a great deal of investigation has been carried out to determine the full range of possibilities of this method.
Early in our experience with pneumoperitoneum, it was pointed out that this method should prove of great avail in the diagnosis of subdiaphragmatic lesions. The full value of the method was not appreciated, however, until opportunity was afforded for its practical application. Pneumoperitoneum has been of such great aid to us on several occasions, in clearing up doubtful diagnoses, that a brief consideration of its use in these lesions seems advisable. While its application in subdiaphragmatic conditions is not as wide as in some of the other regions of the abdomen, because of the limited range of subdiaphragmatic lesions, the information that it gives