Blood test. Gloved hand carrying out an analysis of a sample of blood. This sample is undergoing a test for the erythrocyte sedimentation rate (ESR). Erythrocytes (red blood cells) will settle out of suspension and the timing dial is used to measure how long this takes. This indicates the activity of the blood and is used as a guide for rheumatics who have been prescribed cortisone. The ESR increases in the blood of people with rheumatism.