A relationship between the location of the lesions of multiple sclerosis and the veins of the nervous system was pointed out by Rindfleisch.1 The majority of those who have dealt with the subject have agreed that small lesions usually surround small veins and that larger plaques probably arise by coalescence. A similar relationship between lesions and veins in cases of "post-infectious encephalomyelitis" has recently been pointed out by Finley.2 In other papers of this series the probable cause for such a relationship has been traced. Veins in the neighborhood of sclerotic plaques are often found to be engorged, tortuous, surrounded by blood pigment, thrombosed or obstructed. Thrombosis of veins in the central nervous system invariably produces lesions of the same general type as those seen in "encephalomyelitis" and multiple sclerosis. Presumably, therefore, the vascular abnormality is primary to the parenchymal lesions.3 It is the purpose of the