180 Trans. Acad. Sci. of St. Louis. 
growth at the beginning of puberty, and that precocious boys 
grow faster than dull boys. 
These conclusions may perhaps have. an element of truth, 
but the curves now under examination by no means prove 
their truth. For it must be noticed that the divergence in 
question is scarcely perceptible until ages 14 and 19 are 
reached, ages in which the number of observations is so small 
as to considerably increase the chance of error. No such 
divergence is seen in the case of girls’ weights, in which the 
number of observations in the ages 14, 15, and 16 is very 
much larger.* Bearing this fact in mind, it may be affirmed 
that the comparative rate of growth of dull, mediocre and 
precocious children of the same sex is the same at all ages 
from 7 to 16 inclusive. The data at hand are not sufficient 
to decide whether this law is true ve other ages in the period 
of growth. 
Each boys’ curve in Plate II is characterized by a gradual 
and very nearly uniform ascent until age 13 is reached. Here 
an acceleration begins, indicated by a more rapid rise of the 
curves, and this acceleration becomes still more rapid at age 
14. It is the expression of the change which precedes 
puberty. A similar acceleration is seen in girls, but it takes 
place at an earlier age, the curves beginning their steeper rise 
at age ll. The curves in Plate II are plotted one directly 
above the other. The ordinates for the same age are made 
to coincide in all six curves. It can therefore be readily seen 
whether the period of acceleration begins earlier or later in 
dull than in precocious children. This seems not to be the 
ease. The acceleration in weight preceding puberty takes 
place at the same age in dull, mediocre and precocious children. 
The growth of boys and girls runs a parallel course in early 
childhood. At age 6, boys are heavier than girls, and this 
advantage is maintained for several years. But when the 
difference of sex begins to make itself felt, the relation be- 
tween the weights of the sexes is changed, the boys lose their 
superiority and the curve of girls’ weight rises above theirs. 
'* The extent of this difference in number of observations is seen by 
_ Comparing the columns on the left of Tables No. 2 and No. 3 
