The earliest and simplest version of Jacquet’s Sphygmograph designed to record and measure the pulse at the wrist.
The sphygmograph has a separate leather wrist strap which is attached by means of a screw to the main instrument. A dial adjusts the tension in a spring connected to the manometer which allows the user to vary the pressure on the radial artery. In addition to the main needle recording the pulse there is a second needle used to calibrate time. The clockwork mechanism is wound by the front dial and can be engaged and disengaged from the paper roller by a switch at the side.
Marey’s sphygmograph was made more practical by Dudgeon’s smaller instrument after which came Jacquet’s and other modifications. His later models had optional attachments for a diaphragm driven needle, bringing the role of the sphygmograph closer to that of the Mackenzie polygraph.