A historical review

Ancient concepts of the blood were described by Hippocrates and Galen 2000 years ago in their doctrine of “humors.” It was believed that the body was made up of four humors – blood, phlegm, black bile, and yellow bile – and that these four components had the qualities of heat (Hot-blooded!), cold, moist, and dry. The Galenic concept of the blood prevailed through the Middle Ages. Health or disease were a result of an imbalance, between these...