It is well known that an expanding lesion involving one cerebral hemisphere almost invariably displaces the septum pellucidum and third ventricle toward the opposite side. In recent years a voluminous literature has accumulated in connection with expanding intracranial lesions. Much less has been written concerning atrophic and contracting lesions. Dandy1 mentioned that after destruction of the brain there is ventricular dilatation, sometimes local and sometimes general. He also stated that in such cases dilatation of the subarachnoid space is seen at operation. Foerster and Penfield2 recognized that ventricular displacement occurred in patients with epilepsy and expressed the belief that this was due to "brain-pull or ventricle-pull" from scar tissue. They concluded that atrophy alone could not be responsible. Dyke, Davidoff and Masson3 reported a group of cases of infantile hemiplegia in which there were thickening of the skull and overdevelopment of the sinuses on the side of