168 METABOLISM AND GROWTH FROM BIRTH TO PUBERTY. 



participating in' heat production. Accordingly a comparison of the 

 heat production per square meter of body-surface with children of 

 different weights has a special interest. This comparison is made for 

 the boys in figure 42. 



The wide scatter of points on this chart makes the drawing of any 

 smoothed curve very problematical. About the only clear feature of 

 the plot is that a straight-line curve will not represent the general 

 trend, for there is decided evidence of a gradual increase in the heat 

 production per square meter of body-surface up to about 12 kg. in 

 weight, with a decrease thereafter. This increase, of course, has 

 special interest for comparison with the rise in the intensity of meta- 

 bolism in the first part of the curves shown on several of our earlier 

 charts. This increase thus seems to be clearly established, whatever 

 basis of comparison is employed. 



It is commonly believed that the calories per square meter are 

 constant for all sizes and weights of individuals. The surface areas 

 here shown are not computed or estimated, but are carefully measured; 

 yet on this chart we find variations in the calories per square meter 

 ranging from 647 calories at a weight slightly under 4 kg. to a maxi- 

 mum of 1,278 calories at a weight of about 12 kg. This great diversity 

 occurs with the lower weights, but even after 12 kg., taking for example 

 a point at approximately 28 to 30 kg., we have ranges from 886 to 

 1,205 calories. 



The sketched curve is not unlike that shown when the calories per 

 square meter are compared with the actually measured surface-area 

 (fig. 40), but it is impossible to consider such a wide scatter of obser- 

 vations as indicating more than a general trend. While, as would be 

 expected, a considerable number of points lie within 10 per cent, 

 especially at the higher weight values, the large number of points 

 lying outside these wide limits certainly does not justify the effort 

 to stress this relationship as evidence of a physiological law. 



The calories per 24 hours per square meter of body-surface referred 

 to weight, as plotted for the girls in figure 43, show such a wide diversity 

 in the distribution of the individual points that only a complicated 

 form of curve, which has obviously not been mathematically deter- 

 mined, will serve to indicate the general trend. Characteristics of 

 this sketched curve are the rapid increase in the values up to 10 kg. 

 in weight, and a tendency for the values to decrease thereafter. Con- 

 trary to the -results of the observations on boys, there is with girls a 

 clear tendency in the relatively few observations we have to indicate a 

 fiattening-out of the curve after 22 kg. Still, extreme caution is 

 necessary in considering any data above 30 kg. as of real significance 

 in indicating the general trend, since we have only three points beyond 

 this weight. The two extremely high values between 36 and 40 kg. 

 are the identical observations which showed abnormally high values 



