Some pathogenetic aspects of atherosclerotic lesions. Platelets and atherogenesis. Differences in atherogenesis in different body districts. Regression of arterial lesions in animal models.

The first part of the paper is devoted to the role of platelets in atherogenesis because the new ultrastructural techniques have revealed the morphological basis of platelet "activation". In the second part, the delayed involvement of intracranial vs extracranial cerebral arteries, afferent to the brain is examined on the basis of recent work both in man and in experimental animal models. Regression of arterial lesions is considered in the third part chiefly on the basis of contributions in experimental animals, while more data on regression in humans are expected in the near future.