On no subject is there greater divergence of opinion than on the proper methods of treatment of injuries of the head with their resultant cerebral damage. Fay1advocated an extreme degree of dehydration by the use of hypertonic solutions, both intravenously and by bowel, and rigid restriction of the fluid intake; Munro2advised reduction of pressure and removal of blood by frequent spinal punctures; Sachs3expressed the opinion that spinal puncture is dangerous and contraindicated, and Dandy4advised against the use of both hypertonic solutions and spinal puncture, preferring operative decompression in cases in which there is evidence of a high increase in the intracranial pressure. The reason for the contradictory nature of these opinions is not difficult to find. It is based on ignorance of the mechanism of the cerebral damage attending injuries of the head. The literature abounds with postmortem statistics and clinical opinions