196 METABOLISM AND GROWTH FROM BIRTH TO PUBERTY. 



therefore, more satisfactory results may be obtained in predicting the 

 metabolism from a curve in which the calories are referred to weight 

 than from a curve in which the calories are referred to surface. 



If we employ another line of division, as was done in making com- 

 parisons on the weight basis, and use a surface area of 0.65 square 

 meter as the dividing-line, we find that the average percentage error 

 for boys with this area or above is somewhat lower, being 6.8 per 

 cent, as compared with 7.3 per cent with the division at 0.45 square 

 meter. 



It should be borne hi mind that the curves used for predicting the 

 metabolism were arbitrarily laid on these charts, and represent simply 

 the resultant personal impressions of five skilled workers with metab- 

 olism curves. They are not based upon a mathematical analysis of 

 the points as a whole, and such an analysis has not been attempted. 

 Still, we believe that the curves have a sufficient degree of accuracy 

 to show that there is a definite superiority in the prediction from the 

 curve for calories versus weight to that from the curve of calories 

 versus surface. It thus becomes of physiological interest to recall that, 

 as a result of metabolism measurements upon adults, it is commonly 

 believed that the relationship between weight and metabolism is by 

 no means so satisfactory as the relationship between surface area and 

 metabolism. The comparison of the predicted and measured heat 

 values for these boys appears to show that the prediction of the metab- 

 olism from the weight is not only as good as that from surface, even 

 though we are dealing here with actually measured surfaces, but 

 that it is actually a somewhat better method of prediction for 

 children over 10 kg. Hence these curves and predictions establish the 

 fact that the correlation between weight and basal metabolism is, at 

 least with boys over 10 kg. in weight, of a higher order than the cor- 

 relation between measured body-surface and metabolism. 



In the analysis of the basal metabolism data for 136 men, the 

 average deviation without regard to sign of the predicted from the 

 observed values was in the case of men, when calculated from the 

 body-weight by equations, 97.6 calories. 1 Since the average heat pro- 

 duction of these men was 1,632 calories, 1 this gives an average per- 

 centage deviation of essentially 6 per cent. With boys from 10 to 

 41 kg., we find from the curve of total calories referred to weight a 

 deviation of 6.3 per cent. It is of significance that the marvelous 

 changes in muscle, bone, and fat all changes due to the rapid period 

 of growth through which our study of boys progresses should not 

 alter appreciably the percentage error of prediction from the general 

 curve so as to make it any greater than that with men. In other 

 words, in spite of the great changes due to growth, the average error 

 is hardly greater for boys than with adults, with whom growth altera- 

 tions have practically ceased. 



i Harris and Benedict, Carnegie Inst. Wash. Pub. No. 279, 1919, pp. 180 and 182. 



