DURING POST-NATAL DEVELOPMENT. 519 



leg above the ankle-joint, hut not of the forearm. Moon (1892), Hall (1896), Ernst 

 (1906), and Godin (1910) give data on the girths of the arm, forearm, thighs, and 

 calves in school children which, while differing in details, in general confirm the course 

 of growth by Quetelet's data. According to the data of Ernst, the female thigh 

 begins to be larger than that of the male as early as the eighth year, while Quetelet's 

 data do not show this to be the case before the period of puberty. 



Table L shows that in college students young individuals have smaller muscle- 

 girths than mature individuals of the same stature while the bone-girths are of the 

 same relative size. Short men have relatively larger muscle-girths than tall men, 

 but in women this is not shown. Women have relatively larger thighs and calves, 

 smaller arms and forearms, than men. 



GROWTH AND THE HEIGHT-WEIGHT INDEX OF BUILD. 



The foregoing review shows clearly that there is a close correlation between 

 stature and build and that build varies in definite directions as stature increases 

 and after full stature is reached. These changes are reflected in the height-weight 

 index of build. 



Height-weight index growth-curve. If a given individual were weighed and 

 measured periodically from birth to old age and the height-weight indices were 

 calculated from these measurements and plotted, we should have a curve of growth 

 that would give a much clearer picture of the change in the proportions of his body 

 than we could obtain by plotting curves of weight and stature independently. If 

 we had a large number of such curves we could make use of them for plotting growth- 

 curves typical for the majority of individuals. As it is, we have data for plotting 

 individual growth-curves of this character merely for limited periods in the life- 

 cycle (see charts E, F, G, and H) and are forced to plot typical growth-curves from 

 averages of height and weight of large numbers of individuals grouped according to 

 age. Typical growth-curves of height-weight indices of build based on data of this 

 kind for the whole life-cycle with especial reference to the average American are 

 shown in chart A and have also been reproduced in charts I, J, and K. The data on 

 which these curves are based are too voluminous for publication here. I shall there- 

 fore give merely some of the more important points concerning the growth-curve 

 as a whole and its relations to the chief periods of the life-cycle. 



In chart A a series of indices is given beginning with 1.000 at the left and 

 extending to 0.400 at the right. Beneath each index is a series of numbers to 

 express the weight in pounds of individuals of the stature shown in the column at 

 the left. All individuals in a given column have the same index, but with each addi- 

 tional inch of stature there is a definitely associated addition to the weight which 

 increases with the stature. Thus, in the 0.700 column there is an addition of 3.5 

 pounds to the weight as one passes from a stature of 28 inches to one of 30 inches, 

 while there is an addition of 23 pounds as one passes from a stature of 74 inches to 

 one of 76 inches. The indices and corresponding weights refer to the center of the 

 columns in which they lie. The lines separating the columns represent intermediate 

 quantities. Thus the line between the 0.700 and 0.650 column represents an index 



