anatomist and anthropologist who is best known for his pioneer studies in craniometry (measurement of the skull as a means of establishing the characteristics of human fossil remains).

A professor of anatomy and physiology at the Karolinska Medic-Kirurgiska Institutet, Stockholm (1824–60), he invented (1842) the cranial, or cephalic, index (the ratio of the width to the length—front to back—of the skull, multiplied by 100) as a convenient preliminary indication of the race to which an individual belonged. Retzius also described convolutions of the cerebral cortex (“gyri of Retzius”), a ligament in the ankle, and the veins running from the wall of the small intestine to the branches of the inferior vena cava.