CHANGES IN METABOLISM WITH AGE 



123 



The results in terms of calories per square meter per 24 hours 

 appear in table 43. 



Without exception the values of daily heat-production as given by 

 Aub and Du Bois are higher, and sometimes very materially higher, 

 than those indicated by our equations showing the regression of heat- 

 production per square meter of body-surface by the height-weight 

 chart on age. 



3. COMPARISON OF CHANGES IN PULSE-RATE IN RELATION TO AGE. 



We now turn to a comparison of the changes in another physiological 

 character. It seems desirable in this connection to consider the pos- 

 sible relationship between age and pulse-rate. 



TABLE 43. Comparison of Aub and Du Bois standard normal with daily metabolism given 



by regression equation. 



Our data for adults give the correlations between age and pulse-rate 

 shown in table 44. The partial correlations, given by 



T = 



' ap 



v Y 



ap ' as ' sp 



_ r 2 



1 sp 



T = 



w ' ap 



v f 



ap ' aw ' irp 



VI - 5 



V lr 2 



v J- ' wp 



are laid beside the gross values. 



All the correlations are numerically low. Taken individually no 

 one of the series would be regarded as certainly significant in compari- 

 son with its probable error by any careful statistician. Considering 

 the series as a whole and noting that 9 out of the 11 constants are 

 negative in sign, we consider that there is a reasonable probability 

 that pulse-rate decreases with age. This probability is increased when 

 correction is made for the possible influence of weight and height. The 

 partial correlations, w r ap , s r ap , are the same in sign as the original 

 correlations. 



Since correction for the two most conspicuous physical characters 

 of the individual have left the relationship between age and pulse-rate 



