In this review I shall not confuse authors who were specifically concerned with facial expression in movement (the symptomatology of emotion) with those who have especially studied the signs of inclinations and habits, the study of the shape of the face at rest (properly called physiognomy).

The famous painter Lebrun is among the former, who represented the diverse aspects of facial expression produced by the emotions but without worrying about their laws of morion. There are others who have tried to analyze the expressive movements of the face by identifying the actions of the muscles of this region. I am only going to refer to the work of the latter authors in order to make known how my research differed from theirs; I will speak only of the principal figures among them.

A historical survey

From earliest times anatomists recognized that the facial muscles govern the symptomatic expression of emotions; it was only toward the end of the last century and the beginning of this century that we have specifically studied the way each of these facial muscles contracts under the influence of emotion.

A. In 1792, the learned author of the Dissertation on the Natural Variations that Characterize the Physiognomy of Men of Different Regions and Different Ages, Camper, who was also a talented painter, tried to determine the exact role of the facial muscles in the emotions; he studied the nature of the muscles to a lesser extent than the influence of the cranial nerves on facial expression.