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The first device developed was known as a "galvanometer"(1794), that sensed rather than
measured electricity. In 1849, DuBois-Reymond enhanced the existing device so that it
would measure the current, by adding a two position switch. This device was called a
"Rheotome"(flowslicer).
In 1868, a student of DuBois-Reymond, Julius Bernstein modified the rheotome, so that the
interval between stimulation and sampling could be varied. This was called, "the differential
rheotome" and the first ECG's ever recorded were obtained with it. Most of these were
ECG's of frog hearts, with the electrodes being placed on the heart.
The differential rheotome lacked sensitivity which lead to the development of the "capillary
electrometer", devised by Gabriel Lippmann in 1872. Augustus De'sire' Waller was the first
to discover that the electrical activity of the human heart could be recorded by the capillary
electrometer without opening the chest to expose the heart. He was the first to record the
electrical activity of the human heart in 1887. In his initial paper he called the record an
"electrogram". One year later, he called them "cardiograms". Einthoven introduced the term
we now use, "electrocardiogram".
Einthoven began to develop his own galvanometer in 1900, after being dissatisfied with the
capillary electrometer. This was known as the "string galvanometer" and was introduced in
1903, although Einthoven published a prelimanary report on it in 1901. Einthoven's electrocardiograph was initially manufactured in Germany by Edelmann and Sons of Munich. He
later went with the Cambridge Scientific Instrument Company, Ltd., of London.
The first ECG machine introduced to the United States was an Edelmann String Electrocardiograph brought by Alfred Cohn in 1909. The machine was manufactured in the United
States was designed by Professor Horatio Williams and built in 1914 by Charles Hindle. Alfred Cohn received the first Hindle ECG machine in May 1915. On May 20, 1915, the first
tracing with this machine showed that the patient was having an acute anterior infarction,
although it w 2