ACUTE cerebral disturbances are usually considered to be the result of cerebral - hemorrhage, thrombosis, embolism, or spasm.1Yet in 60 of 100 cases of fatal cerebral infarction Hicks and Warren2were unable to find evidence of mechanical occlusion of cerebral vessels by thrombosis, embolism, or arteriosclerosis. In other words, cerebral infarction without occlusion of the cerebral arteries may occur. For many years the finding of cerebral infarction without cerebral arterial occlusion and the transiency and reversibility of various acute manifestations of cerebral dysfunction3have been explained on the basis of cerebral vascular spasm. At present there appears to be considerable doubt concerning the role of spasm of the cerebral arteries in the production of focal cerebral disorders.4The present study is not concerned with the problem of whether spasm of cerebral arteries may bring about cerebral disorders. Rather, it is desired to call attention to another