Diodrast was injected into the internal carotid artery of a living subject and films exposed during the phase of arterial filling. The carotid artery can be followed through the carotid canal of the temporal bone (below pointer 10), into its typical double bend in the region of the cavernous sinus (above pointer 10). The ophthalmic artery (9) and anterior choroidal artery (17) branch from the carotid before it divides into the middle (18) and anterior (3) cerebral arteries. Both anterior cerebral arteries are filled but the left one is more clearly outlined than the right. (These films have been reproduced through the courtesy of Dr. Earl Miller of the University of California Hospital.)