400 THE SCIENTIFIC MONTHLY 



together. In eleven cases the actual heat productions are 

 higher, while in eleven cases they are lower than the values 

 computed from the equations. The means of the actual and 

 computed heat productions are practically identical. These 

 results show clearly that there is no appreciable influence of 

 vegetarian diet on the basal metabolism. 



Other illustrations might be given. Perhaps the most in 

 teresting is the use of the equations in investigating the differ 

 ence in the metabolism of men and women. This problem, 

 which has attracted the interest of a number of investigators 

 in the past, has been reconsidered from all sides on the larger 

 series of data now available. The results show that the average 

 daily (twenty-four hours) basal heat production of the 136 men 

 investigated is 1,632 calories, whereas that of the 103 women 

 studied is 1,349 calories. Thus the daily heat production of 

 women is about 300 calories less than that of men. But women 

 are smaller than men. If correction for body size be made by 

 expressing heat production in calories per kilogram of body 

 weight, it is 25.7 calories in the men as compared with 24.5 

 calories, or 1.2 calories per kilogram less, in the women. The 

 men show an average daily heat production per square meter 

 of body surface of 925 calories as compared with 850 calories, 

 or 75 calories less, in the women. 



The most critical test of the existence of a difference in the 

 metabolism of men and women is that furnished by comparing 

 the actually measured metabolism of women with that calcu 

 lated from biometric equations on the assumption that they are 

 men of like stature, weight, body surface, age or combinations 

 of these characters. The diagrams in Fig. 8 show the differ 

 ences between the actual metabolism of women (circles and 

 lower lines) and the heat production calculated on the assump 

 tion that they were men of comparable physical characters and 

 age (solid dots and upper lines). Diagrams A-C represent the 

 results given by three different equations. The shaded zone 

 shows a deficiency in the actual heat production of the women, 

 who are classified according to body weight, throughout. 



These and further statistical tests which can not be dis 

 cussed in detail show conclusively that the metabolism of Amer 

 ican women is lower than that of men. Our results show that 

 the differentiation of the sexes is not evident in infancy. They 

 do not confirm the conclusion of Sonden and Tigerstedt that the 

 difference between men and women tends to disappear with 

 age. Instead we find the difference in the metabolism of men 

 and women well marked throughout the period of adult life. 



