During a study of the intracranial blood vessels, it was observed that the extradural portion of the internal carotid artery seemed to differ in structure from the remainder of the vessel, particularly from that portion of the artery usually observed at the base of the brain. The outstanding characteristic of this portion of the vessel was its gross feel, that is, the vessel wall was very crisp and brittle and appeared to be uniformly calcified. The calcification caused the vessel wall to be very rigid, and it was felt that perhaps this calcification within the wall might protect the vessel from the development of occlusive atherosclerosis, since the wall obviously would not constrict or collapse easily. On the other hand it has been surmised by neuroradiologists and clinicians for some time that the parasellar flecks of calcium seen in the plain roentgenograms of the skull reflect atherosclerotic involvement of the