ClipArt ETC
"An instrument which, when applied over an artery, traces on a piece of paper moved by clockwork a curve which indicates the changes of tension of the blood within... a, band by which the instrument is fastened on; b, spring which rests upon the artery; c, adjusting-screw (with graduated head) which regulates the pressure of the spring b according as the pulse is strong or weak; d, d, supports for paper upon which the tracing is made; e, e to engage the paper positively; g, small spring clockwork (incased) by which motion is imparted to the feed-roller e1; h, milled-headed winding key; i, stop-motion; j, tracer attached to the oscillating arm k, which is moved by the rod l that connects this arm with the spring b." —Whitney, 1889

Sphygmograph with All Parts Labeled

"An instrument which, when applied over an artery, traces on a piece of paper moved by clockwork a curve…