130 THE RATE OF GROWTH [ch. 



ward ones may still be growing rapidly, and so making up (more 

 or less completely) on the others. In other words, the period of 

 high positive correlation between stature and increment will tend 

 to be followed by one of negative correlation. This interesting and 

 important point, due to Boas and Wissler*, is confirmed by the 

 following table : 



Correlation of stature and increment in boys and girls 

 (From Boas and Wissler) 



Age 6 7 8 9 10 11 12 13 14 15 



Stature (B) 112-7 115-5 123-2 127-4 133-2 136-8 142-7 147-3 155-9 162-2 



(G) 111-4 117-7 121-4 127-9 131-8 136-7 144-6 149-7 153-8 157-2 



Increment (B) 5-7 5-3 4-9 5-1 5-0 4-7 5-9 7-5 6-2 5-2 



(G) 5-9 5-5 5-5 5-9 6-2 7-2 6-5 5-4 3-3 1-7 



Correlation (B) 0-25 0-11 0-08 0-25 018 0-18 0-48 0-29 -0-42 -0-44 



(G) 0-44 0-14 0-24 0-47 018 -0-18 -0-42 -0-39 -0-63 0-11 



A minor but very curious point brought out by the same 

 investigators is that, if instead of stature we deal with height in 

 the sitting posture (or, practically speaking, with length of trunk 

 or back), then the correlations between this height and its annual 

 increment are throughout negative. In other words, there would 

 seem to be a general tendency for the long trunks to grow slowly 

 throughout the whole period under investigation. It is a well- 

 known anatomical fact that tallness is in the main due not to length 

 of body but to length of limb. 



Since growth in height and growth in weight have each, their own 

 velocities, and these fluctuate, and even the amount of their 

 variabihty alters with age, it follows that the correlation between 

 height and weight must not only also vary but must tend to 

 fluctuate in a somewhat complicated way. The fact is, this corre- 

 lation passes through alternate maxima and minima, chief among 

 which are a maximum at about fourteen years of age and a minimum 

 about twenty-one. Other intercorrelations, such as those between 

 height or weight and chest-measurement, shew their periodic 

 variations in like manner; and it is about the time of puberty 



* I.e. p. 42, and other papers there quoted. Cf. also T. B. Robertson, Criteria 

 of Normality in the Growth of Children, Sydney, 1922. 



