QUOTE : Ancient Egyptians, who made medicinal use of willow bark, which contains the same active ingredient as aspirin does, had a theory. They thought four elements flow in us: blood, air, water, and a substance called wekhudu. They theorized that an overabundance of wekhudu caused pain and inflammation and that chewing on willow bark or drinking willow tea reduced the amount of wekhudu in someone experiencing pain or inflammation and thereby restored his health.