Introduction

One hundred and 50 years ago, a book entitled Mécanisme de la Physionomie Humaine appeared.1 Initially receiving muted and mixed receptions in both the scientific and artistic press, this work has subsequently been recognised as a groundbreaking treatise which was to have a profound influence on the study of facial expression. It was published in 1862 as a single volume, although it had originally comprised two parts: the Partie Scientifique, which was accompanied by 74 photographs, and the short Partie Esthétique, accompanied by 10 photographs, which followed a few months later.2 A second edition appeared posthumously in 1876, but it was only translated into English in 1990 as The Mechanism of Human Facial Expression.3

The present contribution focuses on a debate which began in the Mécanisme but continues to this day, and concerns facial anatomy and expression. The debate centres on the controversial function of a small eyebrow muscle, the corrugator supercilii, yet the background to the debate originated in Greece 2000 years ago, and illustrates how neuroscience can sometimes be informed by the arts.