Kymograph: Principle, Preparation, Use

In 1847, German physiologist Carl Ludwig adapted the chronograph-an astronomical instrument for recording time signals-to track blood pressure. He called it a kymograph or wave writer. In the years that followed, the kymograph became an essential piece of equipment in the laboratories of physiologists and experimental psychologists.
Like the astronomer’s chronograph, the kymograph consisted of a revolving drum that turned at a constant rate by clockwork. The drum carried a sheet of smoked paper onto which a stylus or pen scratched a trail. Typically, there would be more than one pen. One pen would be connected to a pendulum or vibrating tuning fork that traced an undulating timeline, in which each wave stood for a known fraction of a second. Other pens were driven by stimuli such as a pulse, breathing, or the action of key deployed by a research subject.
Preparing the smoked paper, setting up the experiment, and analyzing the results were arts in themselves. This video shows the preparation and operation of a so-called school kymograph from the early twentieth century. The video captures the preparation of the recording drum, including the application of a layer of carbon black to a paper substrate. A pneumatic recorder with a Marey tambour and a Jacquet graphic chronometer are successively attached to the kymograph to record a subject’s input and the timeline. Many sensors were available to measure different things. Here we show the use of a tubular pneumograph to record breathing. The video continues by showing the fixing of the recording with shellac, and it ends with a demonstration of reading the values from the recording. For more information on the individual steps, please turn on the subtitles.