INTRODUCTORY LETTER TO SENATOR MOSSO xxi 



struation ; the acceleration shows itself also in a curve 

 constructed from averages taken from a large number 

 of observations upon many girls, but the variation 

 appears less than it is for the individual and gives 

 therefore an erroneous impression of the actual de- 

 gree of prepubertal acceleration. This falsification 

 necessarily ensues from the individual variations in 

 the age of the first menstruation, for the accelera- 

 tions in one girl may occur at an older age than in 

 another and a younger age than in a third, hence when 

 a long series of observations is averaged the result 

 shows an acceleration much longer in duration, but 



o 



smaller in amount, than is characteristic for the in- 

 dividual. Thus Dr. B. A. Gould found that the 

 stature of American soldiers increased steadily up to 

 thirty-five years to 1.7391 metres, which was the 

 maximum average height for any age. This observa- 

 tion does not prove that the growth period for 

 Americans extends to thirty-five years, for the result 

 noted may be due to more vigorous men growing 

 more and surviving (but not growing) more years 

 than the smaller and weaker men. The average at 

 thirty-five is greater than at thirty because if the 

 suggested explanation is correct the shorter men 

 have died off. This might be decided by statistical 

 study of the relation of the ages at death from dis- 

 ease to stature. It would certainly be worth while 

 to investigate the problem, with a view of ascertain- 

 ing whether there is any correspondence between the 

 length of life and the size of individuals. A positive 



