DURING POST-NATAL DEVELOPMENT. 527 



are lighter than younger children of the same stature. These weight-for-height 

 curves are based primarily on the excellent study of Ethel M. Elderton (1914) 

 on the height and weight of Glasgow school children. In her tables the phe- 

 nomena just mentioned are clearly brought out, although she does not call 

 attention to them in the text. They indicate that children of this age markedly 

 retarded in growth in stature are still more retarded in weight, and that disease 

 or profound physical alterations must be at play. At all other periods groups 

 of individuals retarded in stature tend to some extent to put on extra weight. 

 This is especially noticeable after puberty. On the other hand, although children 

 in whom growth in stature is accelerated do not generally grow equally fast in 

 weight, there are many exceptions at all ages. This is shown especially in the 

 growth-curves of several of the more rapidly growing children studied by Baldwin. 



Adolescence. Above the vertex the parabola for girls is continued to a height 

 of 63 inches at the age of 16. It is very difficult to estimate from available data a 

 curve which may be considered normal for a girl who attains a stature of 63 inches. 

 Girls who will reach a full height of less than 63 inches and girls who will attain 

 more than average stature are averaged together in age-group statistics in such a 

 way that it is impossible to trace accurately the course of development of the aver- 

 age girl who reaches this stature. For an accurate study of this period we need a 

 large number of measurements of individuals from 10 to 20 years of age. Baldwin's 

 studies (1914), while of great value, are based on too small a number of individuals 

 to assist us greatly in this connection, and the same is true of the few other studies 

 on the growth of individuals at this period. For the present the continuation of the 

 parabola of height-weight indices characteristic of childhood up to the period when 

 full height is nearly reached in women seems best to correlate the data at hand. 

 This I have done in constructing the curve of height- weight indices for girls. After 

 the age of 16 the average girl increases very slightly in height, but increases markedly 

 in weight. The growth-curve, therefore, loses its parabolic character and becomes 

 a horizontal line. Empirical estimates of indices for successive age-periods suc- 

 ceeding 16, based on all available height-weight data, are given in table J. 



For American boys the part of the growth-curve above the vertex of the 

 parabola takes quite a different course from that characteristic for girls. For a 

 short period, up to height 59 inches (age 13.5 years in the average healthy boy), the 

 parabola is continued beyond the vertex. There then ensues a period apparently 

 lacking in the growth-curves of most girls, during which the height-weight index 

 remains nearly stationary in spite of very rapid growth in stature. The beginning 

 of this period coincides with the time when (according to Crampton) pubescence is 

 most frequent in boys, and extends to about the age of 16. Crampton has pointed 

 out that the first part of the post-pubescent period is that of most active growth in 

 boys. The period in question is one of very active growth in height. As growth 

 in stature slows down slightly in the sixteenth to seventeenth year, there is a relative 

 gain in weight. This does not appear in individuals who are relatively retarded in 

 growth and whose period of most active growth from the chronological standpoint 

 is prolonged beyond that just described. Such individuals may have a relative 



