hard the heart is working, which is defined as liters of blood pumped per minute divided by surface area.

If surface area is hard to define, nigh on impossible to measure, and not a particularly good proxy for metabolic rate anyway, why is it still used? The main reason is probably the medical profession’s inertia or, more politely, tradition. Medical practice is driven by what works, rather than the best current scientific knowledge. And in truth there is only a small difference in the answers given by calculations based on body area and those based on body weight. Combined with the human body’s ability to stabilize itself, adjust to different feeding and fluid regimes, and process different quantities of drugs, the medical use of body surface area calculations, although arguably irrational, does little or no damage. In the same way, the different doses recommended for adults and children on over-the-counter drug labels are not precise calculations, but the approximation should be harmless. Anyway, the issue is becoming moot: In hospitals, direct measurements of patients’ metabolic weight will probably supercede calculations based on both body weight and area—provided doctors can be persuaded to give up their time-honored mathematical spells.

DuBois’s doubts were in part the result of a long debate with another opponent of the surface law, the physiologist Francis Benedict. By 1930, Benedict had spent two decades measuring metabolic rate in hundreds of humans and other animals. He learned physiology from an American who had shared a lab with Rubner, and in the early twentieth century he extended Rubner’s work by showing that alcohol too could be burned to release energy. The work caused consternation in the temperance movement, especially as it was carried out at Wesleyan, a college in Middletown, Connecticut, run on teetotal Methodist lines. Benedict, himself an abstainer, repaid his debt to sobriety during the Prohibition years, when he turned in the chief bootlegger in his Maine hometown to the authorities. In 1907 he left Wesleyan to run the Carnegie Institution’s newly established Nutrition Laboratory in Boston.

Benedict is remembered for his work on human metabolism. The Nutrition Laboratory built up a detailed picture of people’s energy requirements and how they changed with weight, height, age, and sex.

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