Modification of Dudgeon sphygmograph with tambour dating from around 1890, England. This instrument is made of nickel and has a clockwork mechanism. The sphygmograph, originally invented in 1854 by German physiologist Karl von Vierordt, was used by physicians in the nineteenth century as a means of observing and measuring the pulse externally and non-invasively. A clockwork mechanism allows the pulse wave forms to be traced with a mounted pen.