A sphygmograph is a medical instrument used to measure and record the pulse of a patient. It captures the changes in blood volume within an artery, providing a visual representation of the heartbeat. This device helps healthcare professionals assess cardiovascular health and detect potential issues. Invented in the 19th century, the sphygmograph was one of the first tools to quantify pulse characteristics. It consists of a lever system that translates the pressure changes from the pulse into a graphical output. This innovation laid the groundwork for modern devices like the electrocardiogram and contributed to advancements in cardiology.