William Hammond, the dynamometer, the dynamograph

The dynamometer came into general use by neurologists in the late 19th century. Various dynamometers were developed and adopted by neurologists at that time to measure muscle strength, in keeping with the general trend of adopting instrumentation to distinguish our specialty and aid observation and diagnosis. Many dynamometers were adaptations of the French Mathieu dynamometer, which was initially promoted by American neurologist William Hammond. Another variation, the Mathieu dynamograph, used to graphically record measurements made with a dynamometer, was also initially studied, used, and promoted by Hammond. The high cost of the dynamograph and the lack of demonstrated clinical utility contributed to its limited dissemination. The history of the dynamometer and the dynamograph illustrate both the practical difficulties associated with developing a new instrument, and the numerous modifications that such an instrument goes through, some of which have little to do with practical application.