A historical review of the illustrations of the circle of Willis from antiquity to 1664.

When Thomas Willis published Cerebri Anatome in 1664, he demonstrated within its pages the greatest insight to date into the structure and function of the circular arterial anastomosis that later came to bear his name. For centuries prior, others had described and illustrated the vascular arrangement on the base of the brain with increasing yet incomplete accuracy, and it was not until Willis' treatment of the subject, accompanied by the fine drawings of Christopher Wren, that a complete account of the "circle of Willis" was provided.