NORMAL VARIABILITY 89 
excess of mediocre individuals comes much more 
prominently into view as soon as a larger number of 
measurements can be considered, and the results 
artanged in a different way. 
per cent. 407 
30} iat 
20} — 
1of a F | 
A ese 
9 20 40 60 80 too Ibs. 
FIG. 4. 
The above diagram is constructed from the entries in 
the third column of the accompanying table, which is 
taken from Galton’s ‘ Natural Inheritance.’ It repre- 
sents the variations in the strength of pull (as exerted 
by an archer in drawing a bow) shown by 519 men 
as recorded at the International Health Exhibition in 
1884. Here equal distances measured off along the 
base line represent equal increments in the strength 
of pull of the right hand, and the vertical heights of the 
rectangles erected upon these bases represent the 
percentage numbers of the men examined which 
exhibited each value of the character under con- 
sideration. In this example it is easy to see that the 
central class is the largest, whilst the extreme classes 
contain a comparatively small number of individuals. 
