Marey’s sphygmograph used for monitoring the pulse and heart rhythm. The apparatus would be tied to the flexor wrist and the ivory sensor placed over the radial pulse.
Smoked tracing or plain paper (with ink) was attached to a plate which was moved across the stylus by a clockwork mechanism. Movement of the stylus at the end of its long arm would amplify the radial pulse and record pulse rhythm and amplitude. Signed by Breguet (Paris) and retailed by Leech & Green, No 1 Hamilton Place. Boston. The mechanism remains in perfect working order.