the ratio of the maximum breadth of the head to its maximum length, multiplied by 100. The average, or medium, cephalic index for humans is between 75 and 81 (mesocephalic). A measure below 75 indicates a narrow head that is long in proportion to its width (dolichocephalic); a measure above 81 indicates a head that is wide in proportion to its length (brachycephalic). Also called cranial index. [defined by Swedish anatomist Anders Retzius (1796–1860)]