Injection of air or oxygen into the cerebral ventricles and subarachnoid space has become a recognized and valuable procedure in neurologic and surgical diagnosis.
As a therapeutic measure, injection of oxygen or air into the subarachnoid space by means of lumbar puncture, producing an artificial pneumorachis, has been found of considerable value in the treatment of some of the acute infections of the meninges.
During a small epidemic of meningococcus meningitis in 1916-1917 a few cases were found in which the purulent spinal fluid was obtained with difficulty owing to adhesions or blocking of the vertebral canal. Injections of half strength normal saline solution diluted the fluid and broke up adhesions, permitting a free flow of the purulent fluid. In some of these cases oxygen was injected with the result that an additional quantity of purulent fluid could be evacuated before injecting the antimeningococcus serum. In other cases the air