This roentgenogram was made with the patient in a supine position. The anterior horns and central parts of the lateral ventricles have been visualized by their content of air. The third ventricle (2) and cerebral aqueduct (1) are also well filled. The cisterns of the lateral fossae (14) are clearly outlined by their content of air. The basal cisterns likewise contain quantities of air but the margins of these spaces are obscured. (These films have been reproduced through the courtesy of Dr. Howard L. Jones of the Palo Alto Hospital.)