II. 2 GROWTH 75 



themselves further from the mean than those that are below 

 could approach it, and the more so the faster they were growing-, 

 and conversely. 



We have finally to consider very briefly what little is known 

 of the alteration with growth in the value of the correlation 

 between various organs. Such data as we have indicate that, 

 like variability, this value rises and falls with the growth-rate. 



Boas has ascertained the correlation coefficient (p) in man 

 between weight, stature, height sitting, length and width of 

 head at different ages. Some of these results are tabulated 

 below (Table VIII) ; from this table it will be evident that the 

 value of p decreases, increases, and decreases again. The values 

 are for girls, and the period of increase is earlier than that found 

 for boys. In the chart (Fig. 42) are given the successive values 

 of growth-rate (stature), variability (height), and correlation co- 

 efficient (height sitting and head-length) for boys; the three 

 magnitudes rise at about the time of puberty, and subsequently 

 decline together. Boas urges that if the actual variability is in 

 part the effect of variation in period, this effect will be greater 

 during periods of rapid development. It follows from this that 

 if the various organs of the body are equally affected by a change 

 in the growth-rate, correlations would be closer during periods of 

 rapid growth than at other periods. 



TABLE VIII 



Values of the correlation coefficient, p, during growth for four different 

 correlations. Girls, Worcester, Mass. (Boas). 



Years. Stature and Stature and Stature and Stature and 



Weight. Height sitting. Length of Head. Width of Head. 



7 -73 -74 .30 -21 



8 -76 -79 -36 .15 



9 -80 -82 .35 -16 



10 -83 -83 -37 .16 



11 -81 -84 -37 -25 



12 -77 -82 -38 -27 



13 -73 -83 -38 -37 



14 -67 -82 -30 -25 



15 -65 -79 -26 -22 



16 -60 -74 -25 -10 



It will be noticed that the value of p for the different organs 

 is different, being greater between axial organs stature and 

 height sitting, stature and length of head than between longi- 



