Onsets, Completions, and Skeletal Ages (Hand) of boy 34 and girl 2 may be directly compared and classified, using only those Skeletal Ages which appear immediately below the Onset Profile and the Completion Profile. It may be assumed that differences in ratings due to selection of growth centers from specific regions of the body will be small, according to existing tables of onset age and completion age for centers throughout the body. Accordingly, maturity level ratings by means of the upper portion and lower portion of the Chart, respectively, should be somewhat similar since Skeletal Age assessments are dependent upon Onsets during infancy and upon Completions during adolescence. It is clear that there are some differences in the ratings, but there is substantial agreement. Since a Skeletal Age rating can be made at any age during growth, from Elbow, Shoulder, Knee, or Foot as well as Hand, it seems to be the method of choice when one wishes to study most aspects of skeletal developmental progress during childhood. As stated earlier in the paper, Onsets and Completions -- particularly the former -- provide a different tool or indicator of expectancy in osseous development, each within a limited age period. Such an indicator, or indicators, are needed as means of recognizing specific periods of delay in skeletal developmental progress.

It was stated earlier that one purpose of this study was to extend the analysis of variability of Onset and Completion in each of the 21 growth centers somewhat beyond that provided by the data in Tables 1 and 2. As one approach to doing this, Figures 3 and 4 have been constructed from the mean ages and the individual onset and completion ages for boy 34 and girl 2. The differences between onset age and completion age with respect to the corresponding mean age have been brought into juxtaposition by means of a series of arrows. The data for boy 34 appear in Figure 3, and for girl 2 in Figure 4. The numbering system used in Tables 1 and 2 and Figures 1 and 2 was continued for the 21 growth centers.