The Boulitte Electrocardiograph is an instrument to observe the electrical activity of the human heart. The instrument consists of a projector on the right side, a film camera on the left and a telescopic projection tunnel in between. In the tunnel an electrically conductive string is mounted vertically, between two magnetic coils placed around the tunnel. The projector lamp sends a light beam through the tunnel. This beam will pass the vertical string fed by electrical signals from the human heart. The string will fibrate due to a varying heart signal in the magnetic field.
This construction – developed by fysiologist Willem Einthoven in 1901 in Leiden - is called a string galvanometer as it measures electrical currents. While the string moves it will draw a shadow within the beam. The light beam is projected through a small horizontal slit of the camera. The shadow region in the light projection is captured on a running film. As a result just an ECG on film is delivered.
Remarks ...
The Boulitte Electrocardiograph is one of the first commercial, medical instruments to observe the electrical activity of the human heart.
The electrocardiograph shown here, is the last version made by the French company Boulitte around the 30th of the previous century.