There is a law of surface energy which says that the production of heat in different animals is essentially constant per unit of body surface. The idea that there is an intimate relationship between body surface and production of heat was first observed by French writers1 as early as 1839. The body surface law was definitely formulated in 1847 by Bergmann.2 In 1883, Rubner3 and Richet4 published almost simultaneously the first modern experimental data on the subject, and, because Rubner's work was considered the more important, the body surface law has since been known as Rubner's law.
In the beginning, most physiologists held the conception of a causal relationship between heat production and body surface. From time to time, however, even the most ardent advocates of the body surface law have admitted discrepancies, and its universal applicability has been challenged. Factors such as age, prematurity, prepubescence, sex, athletic training, level