The phenomenon now recognised as the erythrocyte sedimentation rate was first observed by ancient Greeks. They observed the relationship between the sedimentation of red blood cells and fibrinogen (or “phlegma”),and used it as a means of detecting bad bodily “humors”.16 The test used today was introduced in 1918 by Robin Fahraeus, when he recorded the erythrocytes of pregnant women settled more quickly than the erythrocytes of non pregnant women. Normally, erythrocytes settle quite slowly, as the gravitational force of the erythrocyte’s mass is counteracted by the buoyant force of the erythrocyte’s volume.