CHANGES IN METABOLISM WITH AGE. 



Ill 



age. But while age and body-weight and age and stature are very 

 little correlated in adult life, stature and weight, especially the latter, 

 are closely correlated with metabolism. Thus irregularities of stature 

 or body-weight would tend to dilute the correlation between age and 

 total heat-production. 



The reader who has followed the lines of reasoning employed in 

 preceding sections of this volume will at once suggest that there are 

 two ways in which the influence of these disturbing factors can be 

 eliminated. First, we may determine the partial correlation coefficients 

 between age and total heat-production for constant stature and for 

 constant body-weight. Second, we may make the corrections for the 

 influence of body-weight or of both body-weight and stature by ex- 

 pressing metabolism in terms of calories per kilogram or calories per 

 square meter of surface and subsequently correlate these heat-produc- 

 tions per standard unit with age. We have carried out the analysis 

 by both methods. 



TABLE 38. Correlation between age and heat-production per kilogram of body-weight and 

 comparison with correlation between age and total heat-production. 



The partial correlations between age and heat for constant body- 

 weight, 



' ah ' aw" wh 



- 



ah ~ 



Vl- 



and the partial correlations between age and heat for constant stature, 



s^ah = " ~ ~ 



Vl-r a 2 Vl-r sh 2 



are laid beside the gross correlations in table 37. The correlation 

 between age and heat-production per kilogram of body-weight is com- 



