CHAPTER IV. 
DANGERS OF COMPARING MEASUREMENTS OF CHILDREN IN DIFFERENT COUN- 
ES. INFLUENCE OF OCCUPATION AND NATIONALITY OF PARENTS. 
It has been a custom of anthropometrists to compare the 
type-children of cities, states or provinces very different in 
situation and character. Such comparisons may be expected 
always to show that the laws of growth are in their main 
features the same for all children. They cannot, however, be 
expected to give very definite information in regard to the 
relative size of children of different countries or districts 
so long as the social status or environment of the children 
is not more closely studied. The children in the public 
schools are from all classes of society, and it has been 
demonstrated repeatedly that the favored classes differ 
physically from the poor. The children of the prosperous 
have been found to be larger than the children of the poor. 
The comparison of middle values got from two sets of schools 
is therefore open to the objection that the composition of the 
school population may not be the same in both sets. It would 
for example be unsafe to say that St. Louis children are 
larger or smaller than Copenhagen children because the type- 
children in the St. Louis Public Schools are larger or smaller 
than the type-children in Copenhagen, for the difference 
observed may depend on the different composition of the 
school population in the two cities. 
Such comparisons, when rightly made, are not only of 
great scientific interest but are almost essential to the use 
of anthropometrical systems in education. An immense 
saving of time would be made if it were shown that the 
typical height, weight, etc., of children in one city of a 
country could be adopted as the standard for the schools of 
the entire country or even a considerable part of it. And in 
auy one city, the application of the type-values to individuals 
would be much less liable to error if it were known how much 
allowance should be made for the difference between the type 
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