From Lancet, Dec 28 1872, page 915. A combined spirometer, aspiratory and aeroscope”, Alexander Rattray, MD. “For stability and economy of space the cylinders are square; the inner of the thinnest – i.e. lightest – sheet zinc, 6 x 6 in. wide, 13 in. high and accurately counterpoised by weights of lead covered by brass or copper, hanging by 24 in. long silk or catgut cords over two pulley tipped 1/4 in. brass rods, 14 in. long, placed at opposite corners. The breathing tube, 1 in. in diameter and 28 in. long with an ebony or ivory mouth piece, should be attached to the center of the inner cylinder, either by a simple or screw attachment.”
