Porter — The Growth of St. Louis Children. 395 
shows that the sexual difference just noted is not present in 
expansion of chest, or in strength of squeeze, or in 
any head or face measurement except height of face from 
hair-line to point of chin. Boys have therefore a larger ex- 
pansion of the chest, greater strength of squeeze and greater 
length and width of head and height and width of face than 
girls throughout their period of growth. 
An interesting comparison can be made of the duration of 
the period in which girls are larger than boys. It appears 
DURATION OF THE PERIOD DURING WHICH GIRLS ARE LARGER THAN Boys. 
Percentile Grades. 
DIMENSION. 
25 50 75 
At veciee sscnesccevwnssdverwre 35% yrs. 355 yrs. 334% yrs. 
Height standing......06006csucssses 4 " a Site * 
Height slitting ivs.cwes vevwesevesuies 5 _ 5 - "5 Rees 
pall Of ALIS 626s eis chen so rere 375 2A; 2s, * 
Girth of chest......00csccee cess cscs 355; <“* 25 * vs 
that the period is shortest in span of arms and is considerably 
longer in height sitting than in any other dimension. 
The age at which girls begin to be larger than boys differs 
at different percentile grades, big girls (75 percentile grades ) 
beginning to be larger than big boys at an earlier age than 
that at which small girls begin to exceed small boys. A 
difference is seen also in the duration of the period in which 
girls are larger than boys: the small girls keep their 
superiority during a longer time than the larger girls. 
Sexual differences are further displayed in Plates XX XVII 
to XLI, inclusive, in which the percentile curves of both sexes 
are drawn one a short distance under the other, and the points 
at which girls begin and cease to be heavier than boys joined 
by heavy unbroken lines. The early superiority of large 
girls and the relative early loss of their superiority is seen in 
all the plates. The fact that the period during which big girls 
are larger than big boys is shorter than the period during which 
