Anthropological Measurements of Children. 25 



that tlie ineasurements be made and the records kept through 

 two decades, but that the iiiiniber of children measured in 

 the early years of this long period be very great, lest death 

 and desertion so thin their ranks that those remaining to the 

 end shall be too few to yield reliable conclusions. Both 

 methods, when ai)plied to the same material, give identical 

 results with regard to means, including those of subdivisions 

 as well as those of the whole number of observations at any 

 age. The individualizing method does more. 



The importance of the individualizing method has been 

 much emphasized, for the reason that it can give information 

 without which the laws derived from means cannot, in the 

 present state of knowledge, be applied to individuals. Before 

 this application can be made it is necessary to know the 

 degree of probability that an individual who at a given age 

 stands at a certain deviation from the mean of any dimension 

 will show the same deviation at other ages ; for example, the 

 degree of probability that a girl whose height at age 8 is 

 122.06 cm., and who therefore deviates 3.7 cm., or -\-d from 

 the mean (118.36 cm.) of her age, will deviate to the same 

 degree (+<^) from the mean height throughout her growth. 

 In that case the law of growth for the typus at a deviation 

 of _|_ d from the mean is her law of growth. Otherwise she 

 is an exception, and practical regulations deduced from the 

 law for the typus cannot be safely made binding on her. 

 This knowledge, as has just been said, is furnished by the 

 individualizing method, while the generalizing method is of 

 no assistance in this matter. 



The application to individuals of the law of growth of the 

 mean is a subject of immediate practical interest. The con- 

 nection between theory and practical affairs is here unusu- 

 ally short and clear. Were this application possible, the 

 deviations of children from the laws of normal growth could 

 be quickly recognized, and by timely treatuient largely over- 

 come, the evil effects of over-study could be watched and 

 intelligently combated, and systems of education, no longer 



