A little bit of knowledge can be dangerous. Item 24 demonstrates the application of electricity to humans. We are not referring to executions here, just an attempt to explore in more detail the effect of electricity on human muscles, particularly those of the face. Guillaume Duchenne applied electrodes to the face of an elderly man, creating various facial expressions, from happy to scary. His book, Mecanisme de la Physionomie Humaine… provides a photographic as well as textual account of his experiments. Duchenne is considered one of the pioneers in the science of neurology. £12,500 ($20,103).