42 HEREDITY IN RELATION TO EUGENICS 



to inquire how it is inherited. First of all it must be con- 

 ceded that stature is hardly a single unit. It is composed 

 of three elements that would seem to be unrelated, namely, 

 the height of the cranium, the length of the neck and trunk, 

 and the length of the legs. Sitting height is a more signi- 

 ficant measure from the standpoint of heredity; but, unfor- 

 tunately, few persons know their sitting height. A second 

 complication is dependence of stature on age. It increases 

 up to 20 years in the male and about 19 years in the fe- 

 male. Beyond these ages the increase may be neglected. 

 A third complication is that stature is, to a certain degree, 

 dependent on sex. To transmute female measurements to 

 corresponding male measurements Galton (1889) used the 

 method of multiplying them by 1.08 since the mean of 

 male stature is that much greater than the mean of female 

 stature. We can avoid this complication by using, in place 

 of the absolute or transmuted measures, the deviation in 

 each sex from its own mean. The mean stature for the 

 adult males of the white population of the United States 

 may be taken at 69 inches (175 cm); that of females at 64 

 inches (163 cm). Despite all these complications, which 

 tend to obscure the result, we can still seek an answer to 

 the question: What general laws are there of inheritance of 

 stature? 



The first general law is that, in case the four grandparents 

 are very unlike, the adult children will vary greatly in 

 stature, whereas when the grandparental statures are 

 closely alike those of the children will be also. This is shown 

 in the following Table : 



Inches 

 Difference between the shortest and the tallest child: 3 4 5 6 7 8 

 Difference between the shortest and the tallest 



grandparent: 4.6 5.0 6.0 6.5 6.9 7.2 



This law seems to indicate that the reason why in some 



