Raymond Pearl 
25 
Is this agreement between the Hessian and Swedish peoples in the matter of 
brain-weight real, or only apparent and the result of compensating differences in 
the other correlated characters? An answer to this question can be reached in two 
ways ; either by reducing one set to the same " stature-age base" as the other and 
then comparing results, or by analyzing the effects on the brain-weight of the 
observed stature and age differences in the two sets of material. Both of these 
methods depend on the use of characteristic equations, the derivation of which will 
be described further on in the paper. For the present I shall make practical use 
of such equations without further discussion of their derivation or validity. 
Table II shows that in the samples with which we are dealing the Hessians, both 
male and female, average younger and slwrter than the Swedes. Reducing the 
Hessians to the same " stature-age base " as the Swedes, by means of the appro- 
priate equations given on p. 63 infra, the following results are obtained : 
TABLE III. 
The probable brain-weight of a group of Hessian (J $ having the Equation 
same age and stature as the Swedish (J (Total) =1396-480 (23) 
Swedish brain-weight observed =1400'481 
Swedish heavier. Difference ... = 4'001 
The probable brain-weight of a group of Hessian 9 ? having the 
same age and stature as the Swedish $ 9 (Total) =1258-232 (25) 
Swedish brain-weia;ht observed =1252-682 
Hessian heavier. Difference ... = 5-550 
The probable brain-weight of a group of Hessian ^ ^ having the 
same age and stature as the Young Swedish (J =1407-457 (24) 
Swedish brain-weight observed =1415-267 
Swedish heavier. Difference ... = 7-810 
The probable brain-weight of a group of Hessian 9 9 having the 
same age and stature as the Young Swedish 9 9 ••• ••• =1283-540 (26) 
Swedish brain-weight observed = 1269*488 
Hessian heavier. Difference ... = 14-052 
These differences after the stature-age corrections are made are extremely 
small. This is particularly well shown if they are reduced to a relative basis, by 
expressing the differences as percentages of the observed Swedish brain-weight : 
The diff'erence between Total Swedish and Hessians (calculated) =0-29% of the 
observed Swedish brain-weight. 
The difference between Total Swedish 9 ? and Hessians (calculated) =0-44 7o of the 
observed Swedish brain-weight. 
The diff'erence between Young Swedish and Hessians (calculated) =0-55 7„ of the 
observed Swedish brain-weight. 
The diff'erence between Young Swedish 9 ? ^^''d Hessians (calculated) =1-11 7o of the 
observed Swedish brain-weight. 
Biometrika iv 4 
