146 METABOLISM AND GROWTH FROM BIRTH TO PUBERTY. 



stature and metabolism. Furthermore, by means of partial correla- 

 tions, it has been clearly established that each of these factors, weight, 

 stature, and age, has independent relationships. As pointed out 

 elsewhere, 1 



"If a group of individuals of identical weight be examined, the taller in- 

 dividuals will be found to have the higher metabolism. If a group of in- 

 dividuals of the same stature be examined, the heavier individuals will be 

 found to have the greater metabolism." 



In considering the children observed by us, we shall attempt to 

 analyze the metabolism changes upon these various bases. That 

 which has the earliest historic interest and has been most persistently 

 retained, perhaps, is the simplest and most obvious one, namely, 

 that the larger individual has the larger metabolism; hence the 

 metabolism has been referred to the unit of body-weight and com- 

 monly expressed as the metabolism per kilogram of body-weight. 

 This comparison, unfortunately, has the underlying assumption, 

 which we believe to be erroneous, that each kilogram of body-weight 

 has the same heat-producing power. We know that with a thin 

 man the proportions of fat, bone, and muscle differ greatly from 

 those with a fat man. Differences of an even greater order may be 

 noted when a normal, plump, healthy child is compared with an 

 atrophic child, and the clinician hopes to obtain from the physiological 

 studies such an estimate of normality as to allow him to make this 

 comparison. Accordingly, this fundamental assumption of equality 

 in the heat-producing power of the body-mass, with wide variations 

 in the composition of the body, must always be considered as subject 

 to severe criticism. With these mental reservations, we shall com- 

 pare our children of different weights and ages on the basis of the 

 heat production per kilogram of body-weight and examine, in so far 

 as the data permit, the results obtained in the earlier studies. 



CALORIES PER KILOGRAM OF BODY-WEIGHT PER 24 HOURS REFERRED TO AGE (BOYS). 



While the age factor with adults has been shown to have a small 

 influence, in that the heat production decreases annually with age, 

 in the period of growth for boys it can easily be imagined that the 

 influence of age would be larger than with adults. In comparing the 

 total heat production of boys at different ages (see fig. 22), it was 

 found that age changes were intimately connected with weight changes, 

 but in the comparison of the data on the basis of heat per kilogram of 

 body-weight, the weight element is in considerable part eliminated. 

 The heat production per kilogram of body-weight for the boys studied 

 by us at their various ages and weights has been plotted in figure 30, 

 and we have here what may properly be termed a "scatter" diagram. 



1 Harris and Benedict, Carnegie Inst. Wash. Pub. No. 279, 1919, p. 102. 



