Helmholtz pendulum, Berlin, Germany, 1895-1910
The swing of the pendulum stimulates a nerve in a muscle. To calculate the speed, the nerve is stimulated at different distances from the muscle. Nerve stimulation and muscle contraction are recorded on smoked glass paper. Hermann von Helmholtz (1821-1894), the German physicist and physician, used a similar pendulum myograph of his design to study the speed of nerve impulses in a frog. His researches found that the speed of nerve impulses was twenty metres per second. Earlier estimates were far slower. The pendulum was made in the Berliner physikalische Werkstatten GmbH, which translates roughly to English as the “Berlin Physical Workshop”.
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Glossary: Helmholtz pendulum
myograph used to measure the velocity of nerve impulses
An instrument for viewing the interior of the eye, particularly the retina. Light is shone into the eye via a mirror (usually concave) and then examined with or without the aid of a lens. Invented by by Hermann Von Helmholtz in 1850