For the surgeon faced with the practical problem of treating injuries of the head there remain at least two great unsolved problems. These are the vascular alterations related to edema and hemorrhage within the brain substance and the disturbances in circulation of the cerebrospinal fluid. From the field of intracranial tumor surgery have come most of the significant contributions to the present, somewhat inadequate, understanding of the latter problem. The most recent additions to knowledge have concerned herniation of the uncus of the temporal lobe through the incisural notch. The subject has been elaborated on in a series of papers, among which may be cited those of Meyer,1van Gehuchten,2Jefferson,3Reid and Cone,4Moore and Stern,5Smyth and Henderson6and Schwarz and Rosner.7Some of these authors have noted the same phenomenon in association with epidural and subdural hematomas. Thus, it now