The ``dot'' on one end of each arrow indicates extent of difference in months between the child's onset age and the corresponding mean age for the growth center. The ``tip'' of the arrow represents extent of difference between the child's completion age and the corresponding mean age for the growth center. Thus, the alignment of the ``dots'' and ``tips,'' respectively, indicate individual variability of the 21 growth centers of each child with respect to the mean values for these boys and girls. The direction in which the arrow points shows how the maturity level of the growth center was changed at Completion from the level at Onset. When the ``dot'' and ``tip'' coincide, the classification used in this paper is ``same schedule.'' The length of the arrow indicates amount of slowing or acceleration at Completion over that at Onset, and the difference in months can be read roughly by referring the arrow to the age scale along the base of each figure, or more precisely by referring to the original data in the appropriate tables.

The difference between the sequence of Onset of ossification for the sexes governs the numbering sequence in Figures 3 and 4. This difference is readily clarified by referring to Table 1. For example, arrow 17 in Figure 3 portrays the proximal radial epiphysis for boy 34, whereas the same epiphysis for girl 2 is portrayed by arrow 18 in Figure 4. For the boy, this epiphysis was markedly delayed at Onset but near the mean at Completion. Thus, the Span of its ossification was shortened and the center's ability to ``catch up'' in ossification is demonstrated. In contrast, for the girl the epiphysis was slightly advanced at Onset and delayed at Completion. Obviously, the slowing for her may have occurred at any point between Onset and Completion. The Skeletal Age curve in the lower portion of Figure 2 shows that slowing may have occurred for her during the prepubescent period. Length of the shaft of these arrows may be evaluated according to the standard deviation values for each center in Table 1.