Trade card for W H Halse, 'professor of medical galvanism', c 1840s.
© Science Museum / Science & Society Picture Library
'Halse's portable galvanic apparatus' was an early electrical device using a direct current for medical use to give patients electrical treatment. The dial decorated with the Prince of Wales' feathers shows the voltage scale of very weak to very strong with the numbers one to 20. Luigi Galvani (1737-1798) discovered 'animal electricity' in the late 18th century and demonstrated that nerves and muscles in animals function by tiny electrical currents, which can be stimulated by the application of electricity from outside. Electrical treatments were soon in great demand, and were believed to be able to cure all manner of complaints, from gout to paralysis. The term 'galvanise' - to shock or excite into action - takes its name from Galvani.