Increased intracranial pressure is normally propagated throughout the cerebrospinal fluid system and may be measured by a manometer employed in connection with lumbar puncture. Compression of the internal jugular veins causes increased intracranial pressure with immediate rise in spinal fluid pressure. These two statements are facts of considerable importance. It is now generally considered that absence of rise in fluid pressure on jugular compression (positive Queckenstedt1 sign) indicates spinal subarachnoid block, a most important and early sign in spinal cord tumor. More recently, it has been shown that block may also occur and be detected in a similar manner in the presence of tumor of the cerebellar fossa.2 In both of these conditions, the evidence on which a diagnosis of block rests is absence of rise in pressure below the level of obstruction, the increased intracranial pressure being assumed in single puncture below, or proved by