180 METABOLISM AND GROWTH FROM BIRTH TO PUBERTY. 



comparison has been made in figure 49. As has been pointed out, the 

 general trend of the two curves is alike and the two sexes remain 

 at essentially the same metabolism until the area is 0.48 sq. m. From 

 this point the line for the boys rises above that for the girls, and there 

 is no evidence of a tendency for the two lines to cross later. Figures 

 48 and 49 thus give clear evidence of a sexual differentiation between 

 boys and girls, with the boys on the whole showing a higher meta- 

 bolism after the body-weight and body-surface have reached 11 kg. 

 and 0.48 sq. m., respectively. 



Cals. 



TOTAL CALORIES REFERRED TO SURFACE. 



FIG. 49. Comparison of basal heat production of children and 

 adults per 24 hours referred to body-surface. 



The comparison of the total calories to measured surface is, however, 

 a somewhat novel procedure, and physiologists are more accustomed 

 to comparisons of the calories per kilogram of body-weight and the 

 calories per square meter of body-surface referred to weight. Since 

 both these bases of measurement should show a sexual differentiation, 

 if such exist, we have prepared charts giving these comparisons. 

 (See figs. 50 and 51.) The curves for boys and girls in these two 

 charts were taken directly from figures 35, 36, 42, and 43, and are here 

 simply superimposed to bring out the sexual differentiation, which is 

 essentially that noted with the weight curves. 



To make an approximate comparison of the heat production per 

 kilogram of body-weight and per square meter of body-surface between 

 youth and adults, we have laid on these charts lines representing 

 grossly the trend of metabolism with women and men with increasing 



