Atherosclerosis is an arterial disease that is recognized to be the chief cause of death in the United States and in Western Europe.¹ Its importance as a principal cause of myocardial and cerebral infarction and thrombosis has been appreciated for many years. Nevertheless, its cause and pathogenesis remain unsolved. A major problem is that the disease progresses insidiously for many years before symptoms develop, making it difficult to follow the early development of the disease in individual patients, and to relate causally the several types of lesion that have been described. For the same reason, identification . . .