Stethograph or Pneumograph
The stethograph or pneumograph consists of a thick rubber of elliptical shape about three inches long, to one end of which a rigid gutta-percha tube is attached. Labels: h, tambour fixed at right angles to plate of steel f; c and d, arms by which instrument is attached to chest by belt e. When the chest expands, the arms are pulled asunder, which bends the steel plate, and the tambour is affected by the pressure of b, which is attached to it on the one hand, and to the upright in connection with horizontal screw g.
Baker, W. Morrant & Harris, Vincent Dormer Kirkes' Hand-book of Physiology, 13th ed. (Philadelphia: P. Blakiston's Son & Co., 1892) 273