I fra 2006, hare a higher mean variation in ebest girth from set 17 pan of age.

17. Gora nare a lower mean variation for all ages in breathing

* Guna name lower mean variations in strength of right arm, left

arm and upper back for all ages from seven to 18 years.

W la enery trait except in weight and chest girth the boys show a wider range of distribution for these ages.

VII The greatest mean variations for both boys and girls are during the characteristic adolescent ages for each; the smallest are during the earlier periods from seven years to nine years of age.

19. YEARLY INCREMENTS OF Growth of GroUP IN TABLE XXIX

a. Data. The actual annual increments of yearly growth are significant for this group as shown in Table XXXI. “A study of the individual measurements in height reveals different correlations in growth for boys and girls above the median from those below. That is, the rhythms of fluctuations of growth for tall children differ materially from those for short children. This is demonstrated by the norms found, which serve in this connection as a temporary expedient for estimating the relative heights of the children and as a means for dividing them into two general groups, those lying on and above the median and those lying below the median. There are some who cross the median, and others whose curves fluctuate toward or from the median. Those lying above the median height begin and end their periods of acceleration and arrest earlier than those below the median." For increment data see former monograph (27), pages 30 and 31. For new norms for tall and short girls see table XXXVI pages 165 and 166.

"As will be noted, the results give the greatest absolute increment and the greatest average deviations during the adolescent period, beginning at 12 years of age for boys above the median height and beginning at 101⁄2 years for the girls above the median. This marked acceleration continues until 151⁄2 for boys and until 13 for girls. For those below the median height the greatest average acceleration begins at 14 years for boys, and at 111⁄2 years for girls, and continues, for the boys, until 1721⁄2 and for the girls until 152.

"The rhythms and fluctuations of growth in height for the children above the median show that these boys and girls mature in physiological growth earlier than those below the median, since their periods of acceleration and arrest begin earlier and end earlier. There are individual measurements lying on either side of these medians, arranged in all probability in a normal distribution from. the tallest to the shortest for each chronological age. If this is the case, as the individual curves will show, we are justified in making averages or medians only when the average or norm is based on the physiological age instead of the chronological age. A new and very important educational problem is evoked here: How may we formulate a measuring scale for determining the physiological age of the child? A careful study of individual growth curves, based on consecutive measurements, it is hoped, will help to answer this question' (27).

b. Conclusions

I. In yearly increments of growth there are not only sex differences, but a wide range of differences for each trait at various ages. II. The increments are higher in the case of girls than of boys as follows: from nine to 13 years of age for weight; from 11 to 13 years of age for breathing capacity; from eight to 13 years of age for sitting height; from eight to 13 years of age for chest girth; from eight to 13 years of age for strength of left arm. They are inferior at all other ages for all traits and for these ages (eight to 13) for strength of right arm and upper back.

11. YEARLY PERCENT OF GAIN FROM SEVEN TO 14 YEARS OF AGE This table is significant in that it shows the annual increase in increment in growth for the eight physical traits under consideration. The yearly gains in percent can be best gleaned from Table XXXII. It should be noted that

I. For growth in height the yearly increment of percent is very uniform for boys from seven to 16, with a short rise from 12 to 13 years of age; for girls from seven to 13 the yearly increment of percent is very uniform, with the rise from 12 to 13 and a cessation after this age.

II. For growth in weight there is a higher percentage increment