Facialexpressions triggered by electric stimulation. Fig. 4, p. 277 from Mécanisme de la Physionomie Humaine by Guillaume Duchenne, 1862. Crop from http://194
English Figure 25: Not an expression of pain - photograph by Guillaume-Benjamin-Amand Duchenne de Boulogne and Adrien Tournachon (MET, 2013.173.17) determination