CHAPTER VII. 
THE RATE OF GROWTH. 
The Absolute Annual Increase is the gain in weight or height, 
etc., during the twelve preceding months; thus, the absolute 
annual increase in height at age 7 is the gain in weight durin 
the twelve months from age 6 to age 7, obtained by subtract- 
ing the average or median weight at age 6 from that at age 7. 
The absolute annual increase of height standing, weight and 
span of arms is shown in Plate XLII and Tables No. 30, 31 
and 32. In all three, the maximum for girls is at age 13 and 
the maximum for boys at age 15. The same may be said of 
the curves for height sitting, girth of chest and strength of 
squeeze, in Plate XLIII, from Tables No. 33, 34, 44 and 45, 
although the curves are less regular, owing to the observations 
being more difficult than those from which the preceding plate 
was constructed. In all six curves, the small number of ob- 
servations at age 17 and 18 cause the median values at those 
ages to be less reliable than at other ages. 
The Relative Annual Increase is the increase for any year 
divided by the average value at that year; thus, the relative 
annual increase in weight at age 7 is the difference between 
the average weight at age 6 and age 7 divided by the average 
weight at age 6. The relative annual increase gives a truer 
idea of growth than the absolute annual increase, because the 
latter value is entangled with the size of the individual meas- 
ured. The absolute increase is commonly greater in a big 
boy than in a small boy, and yet the rate of growth may be 
the same. The relative annual increase is free of such errors. 
The relative annual increase in strength of squeeze, weight, 
height standing, height sitting, span of arms and girth of 
chest is drawn in Plate XLIV. The gain in weight during the 
prepubertal acceleration is extraordinary in both girls and 
boys, as is the rapid fall immediately thereafter. The quick- 
ness of growth in height standing of boys is slightly greater 
