Darwin, C. R. 1872. The expression of the emotions in man and animals. London: John Murray. First edition. A crop of a picture by Duchenne of he and his assistant (cropped out) "faradizing" (electrocuting) the facial muscles of an insane patient only referred to as 'The Old Man". The experiment was designed to demonstrate the mechanism of facial expression. The whole picture appears in 'Mecanisme de la physionomie Humaine' by Duchenne in 1862.