Blood platelets lack a nucleus. As a result their life span is short and they cannot reproduce themselves. Platelets share these qualities with the red blood cell. Plate lets and red blood cells, nevertheless, serve vital roles in the body. One major function of the platelet is its capacity to aggregate and thereby initiate intravas cular coagulation which often underlies such major diseases as myocardial infarc tion, cerebral infarction, and pulmonary embolism. For this reason in recent years, medical attention has been directed to drugs that inhibit platelet aggregation. Aspirin was the...