Science Art: Appareil Electromedical de G. Trouvet, from La Nature, 1878
This device is “a regulateur des intermittences”, according to La Nature. I’m not sure what “intermittences” are exactly, but Gustave Trouvet was going to fix ‘em by plugging this in. He fixed all kinds of things with his numerous inventions.
I found the picture (by someone named Burgun?) on Wikimedia Commons.