METABOLISM AS AFFECTED BY GROWTH. 173 



Thus, with girls, as with boys, practically all of the earlier work 

 shows a metabolism so much higher than that found by us as to lead 

 us to suspect that strict maintenance of muscular repose was not 

 insisted upon in these earlier observations. Our own results obvi- 

 ously more nearly approach basal, though still not uncomplicated 

 by a possible effect of previously eaten food. 



AGE RELATIONS IN THE HEAT PRODUCTION PER SQUARE METER OF BODY-SURFACE. 



Thus far the consideration of the heat loss per square meter of body- 

 surface for our subjects has been confined to the two bases, weight and 

 measured body-surface. In view of the small and clearly established 

 age relationship in the metabolism of adults, it is important to note 

 whether age has a special effect upon the metabolism of rapidly growing 

 children. As previously pointed out, the differentiating of the age 

 effect is difficult, owing to the fact that age changes are concurrent 

 with weight, stature, and surface changes. Still, for purposes of 

 special discussion in subsequent chapters, it is advisable to consider 

 the heat per square meter referred to age exactly as we have studied 

 the total calories and the calories per kilogram of body-weight referred 

 to age. This is particularly true when it is recalled that, beginning 

 with the days of Andral and Gavarret, special emphasis has been 

 placed upon the influence upon metabolism of approaching puberty; 

 hence in our curves it is desirable to note the ages of the various 

 individuals and to find the general trend of metabolism at these ages, 

 independent of weight or surface, save as the surface area is partly 

 compensated by computing the heat per square meter exactly as weight 

 has been partly compensated in previous comparisons by computing 

 the heat per kilogram of body-weight. 



Figure 45 gives the values for boys for heat per square meter of 

 body-surface referred to age. Recalling that age changes are in the 

 main concurrent with weight and surface changes, it can be seen that 

 the general trend of this curve is somewhat similar to that for the cal- 

 ories per square meter when referred to weight (fig. 42) and when 

 referred to body-surface (fig. 40), exhibiting an increase during the 

 early years up to an age of about 2 years, with a tendency towards a 

 straight-line decrease thereafter. The scatter of individual points 

 makes it difficult to lay on a smoothed curve. We do not defend this 

 use of a straight-line curve and can only take refuge in our oft-repeated 

 statement that the line must be understood to indicate only a trend 

 and may not be referred to with any mathematical exactness. 



As in previous charts, one of the boys is marked as showing un- 

 mistakable signs of puberty, this point lying above our smoothed 

 curve. Attention will be again called to this fact in subsequent 

 discussion of the influence of the prepubertal stage upon metabolism. 



