Kymograph, cased, Europe, 1880-1930

The kymograph is a classic tool of laboratory research invented by the German physiologist Carl Ludwig (1816-1895) in 1847. One of its earliest uses was to measure the blood pressure during physiological experiments. A cannula connected to a U-shaped tube filled with mercury was inserted into the artery of an animal. On top of the mercury was a float attached to a pen. As the blood pulsated, the pen recorded the movement on smoked paper wrapped around the metal drum.

The kymograph is said to have transformed experimental physiology as the graphs produced allowed physiologists to see blood pressure on paper, giving them a permanent record of the experiment. The kymograph was later adapted to record muscle contractions and respiration.