182 A BIOMETRIC STUDY OF BASAL METABOLISM IN MAN. 



and surface, but the errors of prediction are much more nearly equal 

 when equations connecting body-weight and body-surface on the one 

 hand and daily heat-production on the other are used. Thus differ- 

 ences of 41.55 and 98.93 calories in the results of prediction of metab- 

 olism by the use of mean calories per kilogram and mean calories per 

 square meter are reduced to 6.67 and 0.17 calories when equations are 

 used; and differences of 64.75 and 7.37 calories in the deviation of pre- 

 dicted from the observed standards in men and women when mean 

 heat per kilogram and per square meter are used as a basis of predic- 

 tion reduce to 0.85 and 5.65 calories when equations are employed 

 for prediction. 



Finally, comparing body-weight and body-surface as bases of 

 prediction when the more satisfactory equation method is used for 

 prediction, one finds surprisingly little difference between them. For 

 men body-weight gives a square root of mean-square deviation of 

 123.88 calories per day, while body-surface gives 117.21 calories or 

 only 6.67 calories less. For women the difference is only 123.03 122.86 

 = 0.17 calorie per 24 hours. The reader must note that these differ- 

 ences are based on an average metabolism of 1631.74 calories per 24 

 hours in men and 1349.19 calories in women. Thus the differences 

 are less than 0.5 per cent of the total metabolism in each case. 



On the basis of such differences, who is prepared to assert that 

 metabolism is proportional to body-surface but not to body-weight? 



9. PREDICTION OF HEAT-PRODUCTION FROM TWO PHYSICAL 



CHARACTERS. 



We shall now approach the problem of the basis of comparison of 

 the metabolism of various individuals along what we believe to be an 

 entirely novel line of attack. In a preceding section we have empha- 

 sized the view that the true test of any method for the reduction of the 

 metabolism of individuals of different size and shapes to comparable 

 terms is its capacity for predicting an unknown metabolism. This we 

 believe to be not merely a logically sound position, but the one upon 

 which the results of the greatest practical importance can be based. 

 Aside from the purely physiological problem of the value to be assigned 

 to the basal metabolism coefficient for the human species, the precise 

 determination of the metabolism of the normal individual underlies a 

 wide range of practical medical, economic, and social problems. 



Take one illustration merely. A typhoid or goitre subject is placed 

 in the respiration chamber and basal metabolism is calculated from 

 gaseous exchange. This is merely a technical matter. The theoretical 

 question which must be solved before these observational data have 

 any medical significance is: What value should be assigned to the 

 metabolism of this individual on the basis of his measurable bodily 

 characters on the assumption that he is in normal health? In short, we 



