BASAL METABOLISM OF NORMAL MEN AND WOMEN. 203 



of body-weight, they conclude that in middle life the gaseous metab- 

 olism of women is approximately the same as that of men of the 

 same age and body- weight. With children and old men and women, 

 the females have a slightly less (5 per cent) metabolism than the men. 

 The authors also point out that, owing to the larger proportion of 

 body-fat, women would have a metabolism per unit of active pro- 

 toplasmic tissue greater than would men. 



Following the work of Magnus-Levy and Falk there was a period 

 of about 16 years in which little was done on the problem of the differ- 

 ences in the metabolism of men and women. Many observations were 

 made on men, but there were relatively few determinations of basal 

 metabolism on normal women. In 1915, however, Benedict and 

 Emmes 9 returned to the problem, basing their calculations on the 

 89 men and the 68 women designated as the original Nutrition Labora- 

 tory series. In this study they introduced what we have here called 

 the selected-group method of comparison, a method which marked a 

 distinct advance in the comparison of the metabolism of classes of 

 individuals. This method, in a somewhat modified form, we shall 

 employ extensively in this chapter. 



2. COMPARISON OF METABOLISM OF MEN AND WOMEN ON THE 

 BASIS OF GENERAL CONSTANTS. 



In this section we shall base our comparisons of the basal metabol- 

 ism of the sexes upon the constants for the series of individuals as a 

 whole. This method of testing the existence of a sexual differentiation 

 in metabolic activity is not, in our opinion, so valuable as the further 

 development of the selected-group method of Benedict and Emmes in 

 the following section. For the sake of completeness, however, both 

 methods of analysis must be employed. 



Consider, first, the average gross heat-production in calories per 24 

 hours in series of adults. For the 72 individuals of the Gephart and 

 Du Bois selection, the 64 others, and the 136 men the averages are 1623, 

 1641, and 1632 calories, respectively. For the 68 original, the 35 sup- 

 plementary, and the total 103 women the daily heat-productions are 

 1355, 1339, and 1349 calories, respectively. Thus the heat-production 

 of the average woman is roughly 300 calories per day less than that of 

 the average man, when both are measured in muscular repose and at a 

 period 12 hours after the last meal. Thus in adults gross metabolism 

 is markedly less in women than in men. Note, however, that these 

 values are uncorrected for weight, stature, and age in both sexes. 



But women are on the average smaller than men. In either sex 

 large individuals produce on the average more heat than smaller ones. 

 In any discussion of the relation of metabolism to sex it is necessary 

 to correct for this difference in size. Turning to average heat-produc- 



9 Benedict and Emmes, Journ. Biol. Chem., 1915, 20, p. 253. 



