DURING POST-NATAL DEVELOPMENT. 521 



of 0.675. The space between the lines on each side of the 0.700 column may be con- 

 sidered as extending from index 0.675 to 0.725 and divisible correspondingly. In 

 the same way the weight in pounds represented at any given level in a given column 

 refers to the center of the column at that level and the points on either side of this 

 represent weights intermediate between the weight given and the neighboring 

 weights on each side. Furthermore, points between the base of the line for a given 

 stature and corresponding series of weights and the base of the next line represent 

 intermediate statures and corresponding intermediate weights. Thus, a point 

 midway between the base of weight 6S.1 in the 0.700 column and weight 77.4 m the 

 same column would represent a stature of 47 inches and a weight of 72.8 pounds. 

 In a chart of this kind it is possible, with fair accuracy, to plot to stature and weight 

 and read off the corresponding index at the top, or to plot to stature and index and 

 estimate the corresponding weight from the weights near the point plotted. Typical 

 growth-curves for males and for females are plotted in this chart. The curve for 

 males begins with index 0.918 in the 0.900 column at a stature of 20 inches. It 

 takes a vertical course to the level of stature 27 inches and then swings in a parabolic 

 curve to the left, index decreasing as stature increases. The apex of the parabolic 

 curve is reached at stature 56 inches, index 0.413, but soon after the apex is passed 

 the curve changes its character and takes a nearly vertical course until just before 

 full stature is reached, when it curves sharply to the left and finally terminates in a 

 straight line. This portion of the curve represents the increase in weight and index 

 which takes place from the time full stature is reached until the age of 40 or 50 years. 

 In old age there is usually a decrease in stature which would cause the line to curve 

 downwards and a decrease in weight which would cause it to hook to the right. 

 Lack of adequate data, however, has prevented us from plotting this portion of the 

 curve. The curve for females follows closely that of males until the apex of the 

 parabolic curve is reached. The parabolic curve is continued further beyond the 

 apex and the curve to the left appears earlier in women than in men. 



The age at which a given point in the height-weight index growth-curve is 

 reached is a variable factor. At the right of the chart, however, the approximate 

 age is indicated at which the average healthy American male reaches the stature 

 shown at the corresponding level at the left of the chart. For females the age at 

 which a given stature is reached varies somewhat from that for males (tables H, 

 I, and J). 



Unfortunately it is not possible to construct a simple chart which can be used 

 both for the centimeter-gram units and for inch-pound units. A chart similar to 

 chart A may, however, be readily constructed on the metric system. The curves 

 are the same if the proportions of the chart are preserved. As pointed out above, 

 the metric system index may be calculated from the inch-pound index by multi- 

 plying the latter by 0.02768. 



Wcight-for-height curves. As opposed to the height-weight-index growth-curve, 

 based on averages, and intended to show a typical course of development in stature 

 and build, I have designated as weiyht-for-height curves, curves which illustrate the 

 variation in build shown by a group of individuals of approximately the same 



