THE PHYSICAL BASIS OF PRECOCITY AND 
DULLNESS.* 
W. TownseND PorTER. 
(From the Laboratory of Physiology in the St. Louis Medical College.) 
In December, 1891, I received the permission of the St. 
Louis Board of Public Schools to collect physical measure- 
ments of the school children. 
The investigation began on January 4, 1892, and was finished 
the fourth week in March, having extended over eleven of the 
fourteen weeks of winter. The weight, height, length and 
breadth of head, vital capacity of chest, acuteness of 
vision, nationality of parents, and many other facts were 
secured from thirty-three thousand five hundred boys 
and girls. The larger part of the measurements were made 
by the teachers, whose hearty co-operation and efficient service 
in this work should earn them the gratitude of every friend of 
science. 
The great store of facts thus obtained has been used to 
determine the Jaws of normal growth of the children of St. 
Louis in the hope that on this firm ground may be established 
a system of grading which shall take into account the physical 
capacity of the pupil in the apportionment of school tasks. 
An adaptation of mental work to strength is no new idea. 
Many a sporadic attempt has been made to modify the stand- 
ard requirements established for the average boy or girl in 
favor of the exceptionally weak or strong. Such efforts have 
rested in the past on pure empiricism. Only when the laws 
of growth are accurately known, is it possible to know with 
certainty how much the growth of an individual exceeds or 
falls below the normal mean, and without this knowledge the 
* Read before The Academy of Science of St. Louis, March 6, 1893. 
