A CRITIQUE OF THE BODY-SURFACE LAW. 



161 



gives a slightly better criterion of total heat-production than does 

 body-weight. 



We shall now approach the problem from a somewhat different 

 angle. 



7. THE PREDICTION- VALUE OF BODY-WEIGHT AND BODY-SURFACE. 



When the physiologist asserts that heat-production is proportional 

 to body-surface he states that knowing the body-surface of an indi- 

 vidual we also know his basal metabolism. Of course there are tacitly 

 assumed reservations. Pathological factors, the differentiation due to 

 sex, and a number of other as yet intangible influences are supposed 

 to be neglected. Nevertheless it must be admitted that if the assertion 

 that heat-production is proportional to body-surface is of any practical 

 significance, it is tantamount to the assertion that knowing the body- 

 surface of the individual we have the best possible index of his basal 

 metabolism. 



TABLE 56. Comparison of the correlation between body-weight and carbon-dioxide production 

 with correlations between body-surface by the two formulas and carbon-dioxide production. 



We shall start out from the assumption that the best measure of 

 the heat-production of an individual is that which gives the best 

 prediction for an unknown series. Concretely, suppose that we predict 

 the total heat-production of a series of individual men under standard 

 conditions by three different methods. Surely it seems reasonable to 

 regard the method which predicts the metabolism of the individuals most 

 exactly as the best measure. Otherwise the whole contention for normal 

 control series for use in pathological research or in other fields of prac- 

 tical nutrition work is stultified. 



We shall, therefore, predict the daily heat-production of a series 



