ECG

[The electrocardiograph] embodied great mechanical and electrical ingenuity. Its most delicate part was the string galvanometer, initially evolved by Willem Einthoven in 1900-1903, and probably the most sensitive electrical measuring instrument which had been devised by that time; and it used a form of material – the quartz filament – that had first been made less than twenty years before. In order to make visible the tiny movements of the filament, condensing and projecting microscope lenses were used: the lens design was highly mathematical, and modern kinds of glass were required. The light source was a carbon arc, the brightest available point source of light, which had become a reliable device only in the previous two decades. Finally, the movements of the filament, after being projected, were recorded on a photographic plate or film which was coated with a recently developed sensitive emulsion. Had any one of these pieces of technology not been available, the electrocardiograph could not have taken shape. But it was not the ingenuity behind its conception which, in itself, separated the electrocardiography from existing medical technology. It was the combination in one instrument of so many different and new ideas. Twenty years before, so many of its components remained to be invented that the instrument, taken as a whole, was almost unthinkable” (Burnett, 53-54).