176 METABOLISM AND GROWTH FROM BIRTH TO PUBERTY. 



11 years, prior to puberty, the heat per square meter was 909 calories. 

 Somewhat over a year later, when the child was 12 years and 1 month 

 old, the heat per square meter had increased to 1,179 calories. 

 This will likewise receive special consideration subsequently. 



Bearing in mind that age, weight, and surface area changes are so 

 closely interwoven, it is impossible in any of these age charts to 

 emphasize specifically an age influence per se, other than to draw 

 attention to the high point at the age of 1 or 2 years which seems 

 unquestionably to be a specific age influence. 



The extremely few girl subjects in the earlier literature make a 

 comparison with our work impracticable. Such few observations as 

 are on record that can be taken as approximating basal (chiefly those 

 of Magnus-Levy and Falk) would all lie considerably above our general 

 smoothed curve. Special chart representation for these scattered 

 observations hardly seems necessary. 



INFLUENCE OF SEX AND SEXUAL CHANGE ON 



METABOLISM. 



The wide differences in activity and dietetic habits of boys and 

 girls, commonly observed in every household, early led to a belief in a 

 striking difference between the metabolism of children of the two 

 sexes. Unfortunately, many of the earlier comparisons disregarded 

 body-weight and considered age only. While age-changes with 

 both boys and girls are closely followed by weight-changes, for a 

 strict comparison it is obvious that one may not compare a 12-year- 

 old boy weighing 38 or 40 kg. with a 12-year-old girl weighing 30 kg. 



Even the early experiments of Andral and Gavarret 1 are used by 

 the authors as the basis for considerable discussion of the differences 

 between boys and girls. As the authors did not report the body- 

 weights of the children, we can not recompute the data on the better 

 basis of energy per kilogram of body-weight. They conclude that 

 with boys and men there is a steady increase in the carbon-dioxide 

 production from 8 to 30 years, and that between these ages the carbon- 

 dioxide production is greater in amount than that of girls and women 

 of similar ages. Furthermore, they believe that the sexual difference 

 is most pronounced in the adult period (16 to 40 years), the exhalation 

 of carbon dioxide by man during this period being about twice as 

 much as that of woman. The work of Andral and Gavarret is admir- 

 ably presented by Sonden and Tigerstedt 2 in connection with the 

 discussion of their own researches. As the results of Andral and 

 Gavarret or of Sonden and Tigerstedt may not be looked upon as 

 basal in character, the comparison is probably justifiable, since in all 



1 Andral and Gavarret, Ann. d. Chim. et d. Phys., 1843, ser. 3, 8, p. 129. 



2 Sonden and Tigerstedt, Skand. Arch. f. Physiol., 1895, 6, pp. 54 and 56. 



