So I was watching a History Channel documentary on the inspiration for Mary Shelley's Frankenstein and it was talking about how the discovery of electricity was becoming very popular in the scientific community at the time. There was a process around the time called "Galvanization" which was basically a process of applying electricity to something, usually at the time done for health reasons and such (which is pretty much debunked by today's standards). It was discovered that if the process of Galvanization was applied to a frog's corpse, the legs will twitch. Of course, being inquisitive minds these scientists wondered what it would be like if Galvanization was applied to human corpses, and if through Galvanization they could bring a human corpse back to life. Some scientists did obtain human corpses (usually hung criminals) and would apply electricity to them. When electricity was applied to their head, it would cause the facial muscles to twitch and the face to grimace then.

... which is basically what is being depicted here.
Wow... that took too long to explain. I need to choose less esoteric subjects for my pictures. XP