DURING POST-NATAL DEVELOPMENT. 



505 



lengths. At certain periods children of a given stature who are retarded in growth 

 average a greater body- weight than children not so retarded. Such children have 

 some girths relatively increased. This subject is taken up in the following section 

 on the relation of the height-weight index of growth to bodily proportions. 



On the transition from childhood to adolescence, and during adolescence, 

 chronological age, so far as it is correlated with physiological age, has a marked 

 influence on relative bodily proportions. In vertical relative measurements the 

 most marked change is an increase in length of trunk and decrease in length of lower 

 extremities. These alterations, by no means uniform, are illustrated by the follow- 

 ing table based on data from Hastings : 



TABLE 12. 



* Estimates from data on groups of neighboring statures. 



Relative breadths and girths are increased during adolescence. This increase 

 in some measurements ceases when full stature is reached, in others it may continue 

 up to 50 years of age or longer. 



The changes in relative proportions during adolescence and early adult life 

 cause elevations and dips in some of the curves in charts I and J. The position of 

 these elevations and dips depend on the average stature reached by the group of 

 individuals studied. As shown in chart I, they are centered about an average 

 adult stature of 63 inches for women, 67.5 to 68 inches for men. If a group of 

 adults of shorter average height is studied, the elevations and dips shift to the left 

 in each curve; if a group of greater adult height is studied, they shift to the right and 

 as a rule are less marked. The older the group the more marked the dips. In 

 charts I and J the dips are those characteristic of young adults. 



In plotting the curves in charts I and J we have endeavored to illustrate the 

 broader features of typical changes in bodily proportions. In the course of the 

 growth of any given individual or group of individuals minor fluctuations occur 

 which are not indicated in the charts. Periods of relatively rapid growth in length 

 are described as alternating with periods of relatively rapid growth in bulk. In 

 the growth of the limbs rapid increase in length is usually accompanied by a decrease 

 in relative girth. Godin (1903) has described alternate periods of increase in relative 

 length and in relative girth of the long bones of the limbs; he states that these 

 periods are reciprocal for the two osseous segments of a given extremity. Moon 

 (1892) found in boys, aged 11 to 15, rapid increase in length of arm and leg preceding 



