Electrocardiograph made by the Cambridge Instrument Company, England, shown here with its leather carrying case, with some of the apparatus taken out. The electrocardiograph detects and records the tiny electrical signals that coordinate the heart's beats, and which can indicate heart disorders. The signals ripple outwards and are picked up by metal sensors stuck to the skin. Willem Einthoven (1860-1927) developed the electrocardiograph during the early 1900s. Portable versions date from 1928.
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