134 METABOLISM AND GROWTH FROM BIRTH TO PUBERTY. 



along the curve, particularly after 8 months of age. It would appear 

 as if the metabolism during the first 8 months followed with singular 

 accuracy the direction of the curve. At this point we find the second 

 great difficulty in the proper interpretation of this type of curve, 

 namely, the percentage deviations. For example, at the age of 11 

 years, a deviation of half a square either side of the curve corresponds 

 to 75 calories, or, with a basal metabolism of 1,125 calories, a difference 

 of not far from 7 per cent. At the age of 6 months a like deviation 

 has exactly the same numerical value as at 11 years, i. e. } 75 calories, 

 but on the percentage basis this variation at 6 months represents an 

 error of about 20 per cent, since the basal metabolism is considerably 

 less. Hence the seemingly close grouping of points about the general 

 line in the earlier years is only apparent and does not necessarily 

 indicate a greater uniformity in the metabolism. This particular 

 phase must be borne in mind for all of the charts, since it is the 

 common custom of physiologists to consider deviations in metab- 

 olism either side of a so-called normal on the percentage basis and 

 these charts can not be so used. The chief usefulness of the chart in 

 figure 22 is to indicate the tendency for the metabolism to increase 

 rapidly during the first year of life and to rise steadily, though not so 

 rapidly, during the remainder of youth. 



It should be pointed out at this juncture that two of the three values 

 beyond the age of 13 years lie above the projected line. With one of 

 these boys (13 years and 8 months old) signs of puberty were very 

 clearly present. 1 The other two showed no signs of puberty. These 

 facts are emphasized, since subsequent discussion of the metabolism 

 as influenced by puberty is necessary, owing to the great stress laid 

 upon this point throughout the literature, beginning with the earlier 

 studies of Andral and Gavarret. Our data do not permit the dis- 

 cussion of the influence of puberty upon the metabolism, as the obser- 

 vations did not extend to this point, but the accumulation of experi- 

 mental material along this line is now in progress at the Nutrition 

 Laboratory. 



Neither is this the time to consider the possibility of predicting the 

 metabolism of various ages by referring to the general curve or central 

 tendency for the basal metabolism, except as we may lay down the 

 general principle that as the age increases the metabolism increases, 

 and with a reasonable degree of uniformity. 



TOTAL CALORIES PER 24 HOURS REFERRED TO AGE (GIRLS). 



It is the general opinion that boys as a rule are much more active 

 physically than girls, are less controllable, and can less easily acquire a 

 condition of repose. This has a bearing upon any analysis of the 



1 The values for children showing evidences of puberty are represented on the charts by en- 

 closing the point in a square. See discussion of these values on page 183. 



