Platelets and Thrombosis

THE CHARACTERISTICS OF THROMBI, i n particular arterial thrombi, were de-lineated during the latter part of the nine-teenth century. It was shown that the ini-tial step involved the formation of platelet aggregates (1-3). Further growth led to a structure consisting of masses of platelets interspersed with layers of fibrin and red blood cells (3). Within hours the platelet mass usually diminishes, and fibrin be-comes the prominent component (3, 4). In man, thrombus material is usually not available until much of this transformation has occurred. Thus, there has been a tend-ency to lose sight of the basic importance of the platelet. Rightly or wrongly, fibri