A CRITIQUE OF THE BODY-SURFACE LAW. 199 



from body-weight with essentially the same degree of accuracy as 

 when body-surface is used as a basis of prediction. 



Since it has been shown in Chapter IV that both stature and body- 

 weight have independent significance in determining the amount of the 

 metabolism, we have attempted to predict heat-production by the 

 simultaneous use of stature and body- weight. 



With such equations the errors of prediction from stature and 

 weight are about the same as when using body-surface as a basis of pre- 

 diction. Apparently there may be a slight superiority of prediction from 

 body-surface area as estimated from the Du Bois height-weight chart, 

 especially when the superior methods of prediction by the use of linear equa- 

 tions developed in this volume are employed, but on the basis of the data 

 at hand this superiority can not be asserted to be more than apparent. 



The investigation of the validity of the body-surface law has not 

 merely a theoretical interest but possesses material practical impor- 

 tance. While of recent years Rubner's law has taken on the nature of 

 an empirical formula to be practically applied, in origin it was grounded 

 on the hypothesis that thermogenesis is determined by thermolysis. 

 Or, it was assumed that cooling obtains as a cause of heat-production 

 in the organism. As we look at the matter, the "body-surface law" 

 is at best purely an empirical formula. It has furnished a somewhat 

 better basis for the prediction of the metabolism of an unmeasured 

 subject than does body- weight. 



The demonstration in the course of this investigation that by the 

 use of proper biometric formulas the metabolism of an individual can 

 be predicted from stature and body-weight with practically the same 

 accuracy as from body-surface area robs " Rubner's law" of its unique 

 empirical significance in clinical and other applied calorimetry. It also 

 casts grave doubts upon any evidence which its superior power of 

 prediction as compared with body-weight may be supposed to furnish 

 in favor of its being a real physiological law. 



We have shown that the great supposed difference between body- 

 surface area and body-weight as bases of predicting the metabolism 

 of an unknown subject is largely due to the fact that fallacious methods 

 of calculation have been employed. In so far as body-surface area, as 

 estimated from the Du Bois height-weight chart, has any superiority 

 as a basis of prediction, we believe that this has not been due to any 

 causal relationship between body-surface area as such and metabolism, 

 but that it is merely incidental to the fact that body-surface takes 

 somewhat into account both body-weight and stature, each of which 

 we have shown to have independent significance as proximate factors 

 in determining the total metabolism. 



In this volume we have limited our investigation of the body-surface 

 law strictly to its applicability to variations within the human species, 

 in short to its intra-specific and not its inter-specific applicability. It is 



