Wooden box. This is an inexpensive portable version, from about 1960, of the classical 1912 gas analysis apparatus developed by John Scott Haldane (father of JBS Haldane), now remembered for researches into gases in biology. In all the many variations of this equipment, liquid mercury was manipulated by detailed but reliable procedures to control gas volume and pressure, and to absorb gases such as carbon dioxide into alkali. Thus were made possible some very accurate measurements. This particular equipment was used in Addenbrooke's to diagnose thyroid disease, before the days of routine hormone assays. By measuring expired carbon dioxide in the patient's breath, the basal metabolic rate ('the BMR') could be calculated as a guide to thyroid function.