Raymond Pearl 
49 
these characters in the Hessian and Swedish females. The results are shown in 
Table XI, which is arranged in the same manner as the preceding table. 
TABLE XI. 
Probable Male Brain-tueight tvith Stature and Age equal to Observed Female. 
Kace 
Predicted male 
brain-weight 
Observed female 
brain- weight 
Difference 
Equation 
Hessian (Total) 
1357-591 
1259-875 
97-716 
23 
(Young) ... 
1369-431 
1280-202 
89-229 
24 
Swede (Total) 
1370-543 
1252-682 
117-861 
19 
„ (Young) 
1391-624 
1269-488 
122-136 
20 
The mean difference here is 106'736, or in other words we reach essentially the 
same result as before. The general conclusion up to this point then is that there 
is a difference in the mean brain-weight between the sexes of roughly 100 gr. 
after allowance has been made for stature and age differences by taking the mean 
brain-weight of an array of individuals of one sex having for type of stature and age 
the respective means of these characters observed in the other sex. Differences in 
stature and age account for less than one-third of the observed sex difference in 
brain-weight. 
We may next determine what part of the observed sex difference in brain- 
weight is to be accounted for by differences in skull length and breadth. Here 
only one race, the Bohemian, can be used on account of lack of material. Let us 
examine the effect on the mean brain-weight of selecting a group of individuals of 
one sex having the same mean skull length and skull breadth as the opposite sex. 
Making the designated selection first from the males and then from the females we 
have the results shown in Table XII. 
TABLE XII. 
Probable Male Brain-iueight with Mean Skull Length and Skull Breadth 
equal to the Obser^ved Female. 
Eace 
Predicted male 
brain-weight 
Observed female 
brain-weight 
Difference 
Equation 
Bohemian . . . 
1395-631 
1310-914 
84-717 
35 
Probable Female Brain-iveight with Mean Skull Length and, Skull Breadth 
equal to the Observed Male. 
Eace 
Predicted female 
brain-weight 
Observed male 
brain-weight 
Difference 
Equation 
Bohemian . . . 
1.389-736 
1454-839 
65-103 
36 
Biometrika iv 
7 
