A kymograph is a device used to record and visualize changes in physical phenomena over time, such as pressure or movement. It typically consists of a rotating drum covered with paper, which moves at a constant speed. As the drum rotates, a stylus connected to a sensor traces a line on the paper, creating a graphical representation of the data. Originally developed in the 19th century, the kymograph was widely used in physiological experiments to study muscle contractions and other biological processes. It played a significant role in the work of scientists like Carl Ludwig, who utilized it to advance our understanding of physiology and biomechanics.