A mechanism by Dudgeon which recorded the pulse pressure and rhythm at the wrist. Made by Arnold & Sons in the late 19th century.
A sensitive manometer sits on the radial pulse and is amplified by means of a weighted pulley. A clockwork mechanism turns a roller which winds recording paper under the needle to record a trace. Dudgeons device largely replaced Marey’s instrument in popularity because of the relative ease of use and its diminutive size which allowed it to be carried in a pocket. It tended to be the remit of physiologists rather than doctors who were encouraged to rely more on their “finger” (clinical skills) although it was certainly used by many physicians and cardiologists. A fascinating precursor to the ECG / sphygmomanometer which remarkably remains in perfect working order.
Ext Link: The Dudgeon sphygmograph and its descendants (PDF)