CHANGES IN METABOLISM WITH AGE. 



119 



A comparison of the empirical means and the straight-line equations 

 is made in diagrams 20 to 22. The empirical means are very irregular 

 because of the small number of individuals in the higher age groups, 

 resulting not merely from the fact that a division of 103 and 136 indi- 

 viduals into several groups must give small subclasses, but from the 

 fact that the great majority of metabolism observations have been 

 made on individuals between 20 and 35 years of age. 



Notwithstanding this irregularity of the means, these diagrams 

 seem to justify the following generalizations. 



noo 



-1600 



-1500 



'100 



-1300 



+1230 



n 



27 32 J7 42 4-7 52 S7 62 67 72 



AGE 



DIAGRAM 20. Mean total daily heat-production of men and women 

 classified according to age. 



^ There is far better agreement between the empirical and the 

 theoretical means when heat-production is expressed in calories per 

 square meter of body-surface than when given in terms of gross heat- 

 production. 



(2) From the graphs alone it is impossible to decide whether the 

 expression of metabolism in calories per kilogram of body-weight has 

 resulted in an improvement in the agreement of the empirical and 

 smoothed means over that which is found when heat-production is 

 recorded in total calories per 24-hour periods. 



(3) The regression lines for men and women lie much closer together 

 and are more nearly parallel when heat-production is expressed in 

 relative terms, i.e., in calories per kilogram or calories per square meter, 

 than when given in terms of gross heat-production. 



