the girls, except from approximately 12 to 13 years of age, on the average. The girls reach their maximum period of growth earlier than the boys. With both groups there is a tendency for the curves to fan out as the age increases. In both the boys' and girls' curves there is a slight adolescent acceleration which appears earlier for the girls than for the boys, with a slight retardation before this pubescent acceleration. For both boys and girls at the pre-adolescent period, the pubescent acceleration causes the curves to approximate in appearance a series of concentric ares of varying sizes, where a chronological point, say 12 years, in the lower ares, is reached later than a corresponding point in the upper ares. The taller boys and taller girls both reach their periods of maximum growth and periods of diminution of growth earlier than do the shorter boys and girls; this is more apparent with the girls than with the boys in this particular chart. In cases where there are periods of retardation during early adolescence, this is usually followed by a period of rapid acceleration during adolescence. If the increment of growth before adolescence is relatively uniform, this uniformity tends to persist throughout adolescence, resulting in some instances in growth curves in height becoming practically a straight line.

With both boys and girls the curves assume a railroad appearance; each individual boy and girl holds approximately his or her relative position in the group for the periods from six to 17 years of age, with little crossing of the individual curves. (This explains in graphic form the high correlations found between the heights at different ages for the same individual child, p. 140) In the 1914 bulletin, it was discovered that the increment of growth in height is comparatively uniform for each individual, so that the growth curves enable one to prophesy with a high degree of accur acy how tall a child of normal growth will be in the subsequent age, providing his or her relation to a given median or norm is known. In brief, tall children do not become short; neither do short children, as a rule, become tall under normal conditions. This discovery has been verified again with these new data.

(2) Weight, Boys. Girls. The individual weight curves in Chart XV are for the same group of individuals whose height curves are given in Chart XIV. It will be noted that there are strikingly significant differences between the growth in weight and the growth in height. The trend of the weight curves is toward concavity.

rather than toward convexity. There is more individual variation in weight and more variation in the distribution of individuals within the group, although as a general rule heavy children remain

relatively heavy during the period studied. Unlike height, weight may exceed or fall below the previous measurement-a fact that shows the urgent need of vigilance and the value of consecutive examinations on the part of school authorities.

Girls, as a rule, are relatively heavier for their height than boys,

Weight in Kilograms and Pounds

and therefore the weight-height indices are higher for girls than for boys. The individual weight curves show that the pre-adolescent acceleration in weight precedes, as a rule, the acceleration in height,

BO 176.4

70

154.3

60

32.3

50

40

88.2

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66.1

20 44.1

10 22.0

INDIVIDUAL

GROWTH CURVES IN

WEIGHT

BOYS -GIRLS www.NORMS (Baldwin)

Age in Years

Chart XV

and that this stage in development is earlier for tall boys and tall girls.

(3) Sitting Height, Boys. Girls. For this group of American children it is apparent that there is a very close relationship between standing and sitting height for the same individual, since the distribution of the curves for height sitting is almost identical with the

distribution of the curves for height standing, though the relationship decreases slightly with age. The general trend of the curves is also very similar. These conditions are true, in general, for both boys and girls, but the relationship is closer for boys than for girls. The general conclusions outlined for standing height apply also to sitting height and there seem to be no marked differences between the relationship of the two for tall boys and girls and short boys

and girls. There are, however, some interesting variations in the sitting height of children of the same stature, even in the same family. Sometimes the sitting height is indicative of definite racial characteristics, as for example the short trunk and long legs. of the average American and the reverse condition in those of French descent. The boys and girls of tall sitting height as a rule have good or superior breathing capacity. The sitting height to the notch of the manubrium is probably a better standard for growth than the usual standing height, since the length of the neck and the size of the head are eliminated.

4. Chest Girth, Boys. Girls. An approximately close relation

ship exists between the distribution of individual growth curves for chest circumference and height, but the relationship between breathing capacity and chest girth is not so close as has been generally assumed, though on the whole the general trend and positions of the two curves for each individual are similar. How far one should be taken as an equivalent of the other is an important question; the difference is more marked with girls than with boys.

Although the so-called "normal" chest girth has been selected, the chest girth is affected by breathing, the curves showing fluctuations which are probably due in part to the difficulty of making accurate measurements of the amount of residual air in the lungs or the change in subcutaneous fat or muscle.

The chest girth of girls is relatively less than that of the boys. except at adolescence, and there is a cessation of development considerably earlier than in the case of the boys.

(5) Breathing Capacity, Boys. Girls. The individual growth curves for the 17 individuals whose height curves are given in Chart XIV and whose weight curves are given in Chart XV are distrib