One of the most useful and practical indices of growth is the weight height coefficient, which expresses the comparative solidity or robustness of the individual, and therefore, other things being equal, his general nutrition.
The lowest ratio in this group of boys is .15 at six years, and the highest .40 at 1712 years of age. There is little or no apparent difference, as a rule, between the tall boys and the short boys, except that the acceleration begins earlier for tall individuals. For example, if we take 0.23 as representing a given physiological stage of development, it will be noted that the time shifts chronologically in a fairly uniform manner between 7 and 8 years of age with No. 1, to 1412 years for No. 14.
It will be noted in the boys' lung capacity curves that No. 9 in the first chart, who is relatively heavier than the others for his height, also has more lung capacity. This is significant since the other boys hold approximately their relative places for height, weight and lung capacity.
The boys have greater lung capacity than the girls, on an average, for all periods except at about 13 and 1312 years of age. The develop-
