In 1791, Galvani, in Italy, first showed electromotor activity in the leg muscle of the frog (1). Action potentials of skeletal muscle were later found by several physiologists in the 19th century and in the 1870s, electromotor phenomena were found in heart muscle using exposed animal hearts. Lippman in Paris, in 1872, invented the capillary electrometer which could demonstrate cardiac electrical activity without having to expose the heart (2). This sensitive but sluggish apparatus consisted of sulphuric acid and mercury in a capillary tube with wires at each end (Fig. 1).