STATE OF NUTRITION. 197 



the metabolism of man and animals, investigators have attempted to 

 find if uniformity existed in the metabolism of different human indi- 

 viduals and even different species of warm-blooded animals. In the 

 experiments made with the respiration calorimeter at Wesleyan Uni- 

 versity direct measurements of the heat production of man were made 

 for the first time and the complete uniformity of direct and indirect 

 calorimetry was first estabhshed. In common with other investigators 

 at that time, no attention was paid to the importance of controlling the 

 minor muscular activity in the restricted confines of the respiration 

 chamber. The data obtained in these measurements were carefully 

 searched to find if evidence existed of uniformity in the metabolism of 

 individuals. It was soon found that with individuals inside the respi- 

 ration chamber, living substantially the same routine of life, the naetab- 

 oHsm was relatively constant with the same individual from period to 

 period. This was made the subject of discussion by one of us in con- 

 junction with Dr. T. M. Carpenter,^ but even at this time differences in 

 individuals, and particularly in individuals of different weight, were 

 strikingly emphasized. 



Recourse was had by earlier writers to the comparison of the metab- 

 oHsm on the basis of per kilogram of body-weight, on the theory that a 

 large animal would give off more heat than a small animal, and heat 

 production per kilogram would thus be a better index than heat pro- 

 duction per individual. This, of course, is based upon the arbitrary 

 assumption that each kilogram of weight has the same heat-producing 

 power. Although for general purposes the heat production per kilo- 

 gram of body-weight was found to be reasonably constant, many 

 writers were of the opinion that the heat production per square meter 

 of body surface was a much better index than the heat production per 

 kilogram of body-weight. For such comparisons the body surface was 

 computed by the now archaic method of Meeh,^ using the formula 

 12.312 -v^body-weight.2 Much of the evidence impHed that the dis- 

 crepancies between individuals were in large part eliminated when the 

 calculations were based upon body-surface. Indeed, many writers 

 considered that they were so completely eliminated as to estabhsh a 

 "law of surface area." 



The so-called ''law of surface area" has had a rather remarkable 

 history. Warm-blooded animals have a temperature which is usually 

 much higher than the environment. It was argued that heat was lost 

 to the environment in proportion to the extent of the body-surface and 

 that for equal surfaces the heat loss would be very nearly the same. In 

 other words, since the heat produced inside the body very nearly com- 

 pensates for the heat lost, thus resulting in a practically constant body 



1 Benedict and Carpenter, Carnegie Inst. Wash. Pub. No. 126, 1910, p. 105. 

 * Meeh, Zeitschr. f. Biol., 1879, 15, p. 425. 



