INTRODUCTORY. 3 



The desirability of applying the biometric formulas to the steadily 

 increasing volume of data on basal metabolism in man has more than 

 once suggested itself. Thus, as early as July 1915 Professor August 

 Krogh, of Copenhagen, in his ever stimulating correspondence, urged 

 that the data accumulated by the Nutrition Laboratory were already 

 so extensive that the modern statistical formulas might profitably be 

 employed in their expression and interpretation. After the manuscript 

 for this volume was practically completed, a paper by Professor Armsby 

 and his collaborators 4 appeared, giving the correlation between body- 

 weight and daily heat-production and body-surface area and heat- 

 production. 



Fortunately the number of individuals whose basal metabolism has 

 been determined is now fairly large. Dealing as we have in this volume 

 with individuals measured at the Nutrition Laboratory, or by those 

 who have been associated with the Laboratory, we are able to discuss 

 the constants of nearly 250 adults and of about 100 infants. In the 

 past these have been treated almost exclusively by the simple method 

 of averages and graphic representation. But a series of metabolism 

 constants, like other biological measurements, show differences among 

 themselves. These differences must be due to either inaccuracies of 

 measurement, or must represent real physiological differences between 

 the individuals considered. That the latter rather than the former is 

 true seems evident from the fact that technical errors in the making of 

 the measurements have in all careful work been reduced to a minimum 

 by the frequent use of physical tests of the apparatus, by the measure- 

 ment of standard combustions, and by other precautionary measures 

 which have placed the data of gaseous metabolism among the more 

 accurately controlled of the physiological measurements. That the 

 differences between the measurements of individuals are of the nature 

 of real biological difference rather than of errors of observation is also 

 clear from the fact that such attempts as have been made to obtain a 

 more precise average metabolism constant by reducing the total heat- 

 production to calories per kilogram of body-weight or to calories per 

 square meter of body-surface have effected a material reduction in the 

 amount of variation in the measures of the actually observed metabol- 

 ism of individuals. Notwithstanding this correction for the physical 

 characteristics of the individual due to the reduction of the gross heat- 

 production to calories per kilogram or calories per square meter of 

 body-surface, the variation in the metabolism constant is not entirely 

 eliminated. It seems necessary, therefore, in any thoroughgoing inves- 

 tigation of metabolism in man, to take account of the variation from 

 individual to individual, as well as of the general average. Further- 

 more, the fact that some lessening in the differences in the metabolism 



* Annsby, Fries, and Braman, Proc. Nat. Acad. Sci., 1918, 4, p. 1. See also Journ. Agric. 

 Research, 1918, 13, p. 43. 



