118 A BIOMETRIC STUDY OF BASAL METABOLISM IN MAN. 



The reader personally unacquainted with the difficulties in the 

 measurement of human metabolism may consider these results numer- 

 ically very discordant. We have purposely set down the full series of 

 equations to bring out this range of differences. To us considering 

 the great difficulties of measurement, the wide individuality of the 

 subjects in physique, diet, and life-history, and the (statistically) small 

 number of individuals considered the results seem remarkably con- 

 sistent. There are differences, to be sure, but so there are in the first 

 determination of any chemical, physical, or astronomical constants. 

 As the number of determinations increases it will be possible to give 

 the statistical constants measuring the influence of age upon metabol- 

 ism in men and women as a class with ever increasing precision. 



TABLE 42. Alteration of metabolism with age. 



The theoretical significance of these results will be discussed in 

 the final section of this chapter. From the standpoint of practical 

 application it is important to determine whether or not in the age 

 range of adult life covered by our data, changes in metabolism with 

 age can be sufficiently well represented by the slope of a straight line. 

 If so, correction for age in clinical calorimetry will be a relatively 

 simple problem. 



Straight-line equations for a number of the series have been given 

 on pages 114-115. These are based on observations ungrouped with 

 respect to age. For purposes of graphical representation it has seemed 

 desirable to class the individuals in quinquennial groups. Table 42 

 shows the method of grouping, the number of individuals, and the aver- 

 age heat-production in total calories, in calories per kilogram of body- 

 weight, and in calories per square meter of body-surface by the Du Bois 

 height-weight chart for 24-hour periods. 



