This device was invented by Emil Heinrich du Bois-Reymond (1818-1896) and produced by Charles Verdin of Paris, France. The 'Frog-pistol' was invented to demonstrate the stimulation of nerves in a frog's leg. It works in the following way. A frog's leg is mounted on the glas plate inside the tube, with the nerve ends exposed and connected to the keys on the top of the pistol grip. When these keys are depresed, a contact is made and the muscles in the leg contract.
© Science Museum / Science & Society Picture Library