50 THE GROWTH OK THE BRAIN. 



1 686-^500^- 3 '37 fold, and the volume of the body 

 7 1*08-7-3 '44 20*66 fold. If during this period of thirty 

 years the geometrical relations at birth had persisted, 

 the increase in volume of the body would have been 

 proportional to the cube of the increase in stature, but 

 the cube of 3*37 is 38*27, which is almost twice as much 

 as the increase in volume which has been observed. It 

 is thus shown that the geometric relations existing at 

 birth must change during the progress of growth. For 

 this reason the study of stature, important as it is, does 

 not furnish data from which the changes in the entire 

 body can be inferred except in a most general way. 



In dealing with the data relating to change in weight, 

 some care must be exercised in selection of the observa- 

 tions to be employed as standards. Of course, since the 

 different races of mankind differ widely in their final 

 weight, and probably in the details of the manner in which 

 they attain it, the individuals who are to be tested by 

 reference to a chosen standard, should be compared onl}^ 

 with data derived from the study of those belonging to 

 the same race and growing up under conditions as 

 nearly similar as it is possible to have them. There have 

 been already gathered in Denmark, Germany, Sweden, 

 England, Russia, and the United States, a very large 

 number of observations on the weights of school-children 

 at different ages. These observations are unfortunately 

 limited in range to the school ages, viz., from about 

 four to twenty years, and thus leave out the important 

 years before four and after twenty, the record for which 

 it is desirable to have in order to compare, from birth 

 to maturity, the growth of the central nervous system 

 with that of the body. For the following discussion 

 it seems best to employ but a single series of observa- 

 tions, and for this purpose those on the general popula- 

 tion of Great Britain published by Roberts have been 



