C1913 Boulitte Registering Percussing Hammer

C1913 Boulitte Registering Percussing Hammer


C1913 Boulitte Registering Percussing Hammer



Country of manufacture


Categories: Medicine, Diagnostics


An extremely rare example of a registering percussing hammer made by Boulitte early in the 20th century. It is shown in their 1913 catalog and described as a Verdin hammer for electrically registering the moment of electrical impact on the patella tendon.
I have been able to draw on the expertise of Richard Belser to provide a more detailed explanation of this instrument:
What sets it apart from a normal percussion hammer is the mechanical mechanism attached to the handle, which I interpreted to be an electric switch.  Such a switch activated at the moment of impact would have been used to produce a pen deflection on a recording device (probably a kymograph) to mark that point in time.  The latency until a resulting nerve or muscle response (recorded on the same device using additional electrical or mechanical sensors on the body) could then be measured.​ As you can see, the arm on the side of the handle is held back against a stop by a leaf spring, and would be thrown forward upon impact, probably opening a circuit between the arm and the rear stop.  The ball on the threaded shaft is a sensitivity adjustment.  By moving it up toward the distal end of the arm, you would facilitate its forward motion and thus increase the sensitivity of the switch, causing it to open with less impact force.  Moving the ball lower down would make it harder to overcome the leaf spring tension, thus making the switch less sensitive, and requiring more force to produce a mark on the recording.  It’s very simple really.  A nice elegant design.Nerve conduction latency studies using exactly this principle remain a very common diagnostic tool for assessing nerve and muscle disorders, albeit using more modern technology.


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US M&R Gordon

Michael and Roberta Gordon have been dealing in medical and dental antiques for four decades. They have helped build a number of major private collections and have contributed to the holdings of many museums. They also deal in other scientific and technology related items, including calculating instruments, office machines, patent models and wine-related accessories such as corkscrews. ROBERTA GORDON IS A SKILLED RESTORER WHO CAN HELP YOU WITH ANY INSTRUMENTS AND CASES THAT NEED ATTENTION. Feel free to contact them for details at: mgordon1940@gmail.com or 718-623-6777