1912.] The Intensity of Natural Selection in Man. 473 

 Table I. — Males. 



Years of life-table. 



1838—1854 ... 

 1871—1880 ... 

 1881—1890 ... 

 1891—1900 ... 



Means 

 S. D.'s 



163 -50 

 158-58 

 161 -04 

 171 -86 



134 -73 

 127 -58 

 104 -26 

 94-01 



= 10 •< 



50 -38 

 52-19 

 52 -88 



From these data we further deduce : — 



r ic = -0-6359 

 r ie = +0-5620 

 r ce = -0-9941 



These lead to the partial correlation coefficient of infantile and child 

 death-rates for constant environment 



e r ci = -0-8605 ±0-0875. 

 Notwithstanding the small number of life-tables dealt with this is most 

 substantially significant. With our measure of constant environment, every 

 increase of the infantile death-rate is accompanied by a marked decrease in 

 the death-rate of the survivors in childhood. 

 The multiple regression equation is 



c = 115-145- 0-3748 (t-163-744)-ll-0038(e-51-21) 

 = 740-021-0-3748 i-ll-0038e. (1) 

 Thus for constant environment, i.e. e constant — 



Increase in child death-rate = — 0"3748 (increase in infantile death-rate). 

 Or, looked at in another way — 



Percentage decrease in child death-rate = 0-533 (percentage increase in 

 infantile death-rate). 



In other words if you increase the infantile death-rate by 10 per cent, you 

 decrease the child death-rate by 5 - 3 per cent. 

 • The approximation of the method is indicated by the following table : — 



Period. 



Observed c. 



Calculated c 



1838—1854 .. 

 1871—1880 .. 

 1881—1890 .. 

 1891—1900 .. 



134 -73 

 127 -58 

 104 -26 



135 -26 

 126 -21 

 105 -38 

 93 -73 



+ 0-53 

 -1-37 

 + 1-12 

 -0-28 



