History of aspirin other studies from the 1960s to the 1980s established aspirin's efficacy as an anti-clotting agent that reduces the risk of clotting diseases. Aspirin sales revived considerably in the last decades of the twentieth century, and remain strong in the twenty-first with widespread use as a preventive treatment for heart attacks and strokes. Medicines derived from willow trees and other salicylate-rich plants have been part of pharmacopoeias at least dating back to ancient Sumer. The Ebers Papyrus, an Egyptian medical text from ca. 1543 BCE, mentions use of willow and myrtle (another salicylate-rich plant) to treat fever and pain. Willow bark
Birch bark from live trees is harmful to tree health and should be avoided. Instead, it can be removed fairly easily from the trunk or branches of dead wood, by cutting a slit lengthwise through the bark and pulling or prying it away from the wood. The best time for collection is spring or early summer, as the bark is of better quality and most easily removed. Removing the outer (light) layer of bark from the trunk of a living tree may not kill it, but probably weakens it and makes it more prone to infections. Removal of the inner (dark) layer,