Robert Bennett Bean 383 
tively smaller than the Caucasian, and the left is relatively and absolutely 
larger than the right. The female Caucasian is similar to the male 
Caucasian and the male Negro is similar to the female Negro, but in a 
less degree. It might have been supposed that the fissure 
of Rolando is further posterior in the Negro brain than in_ the 
Caucasian, and that the small size of the frontal lobe in the Negro is 
an apparent and not a real deficiency of brain matter, but the above meas- 
urements indicate that the frontal lobe and all the brain matter an- 
terior to the fissure of Rolando is less in the Negro than in the Caucasian. 
As the gyrus rectus is apparently larger in the Negro than in the Cau- 
casian, and the gyrus frontalis inferior is larger in the Negro than in the 
Caucasian, and as the frontal lobes in the Negro appear larger than 
they really are, owing to the projection downward of the convolution 
just mentioned, as well as to the projection upward of the superior 
erbital plates and the gyrus frontalis superior, if it be true that 
the motor area and the left gyrus frontalis inferior are larger in the 
Negro, then it must be true that the anterior association center is con- 
siderably smaller in his case than in the Caucasian, because even the 
apparent size of the whole frontal lobe is smaller in the Negro. 'That the 
anterior association center is smaller in the Negro seems plausible when 
the corpus callosum is examined, in which the racial distinction is more 
pronounced than in the brain outlines, the anterior end (genu) being 
distinctly smaller in the Negro. 
Corpus CALLOSUM. 
The cross section area of the corpus callosum is measured with the 
planimeter from outlines made directly on glass, and from other outlines 
made on paper by projection. These areas are given in Table I, with 
the brain weights taken at the time the outlines were drawn. Measure- 
ments made from Retzius” photographs and drawings of brains by others 
are given in Table I’, with brain weights, when possible, for comparison. 
Chart V is made up from these two tables, the brain weights (abscisse) 
being given in grams, and the areas of the corpora callosa (ordinates) 
in square centimeters. There is in general an increase in area of the cor- 
pus callosum with each increment of brain weight. There are, however, 
many individual exceptions. For instance, one Caucasian brain weighing 
about 1100 grams has a corpus callosum of about 8 square centimeters 
area, while another brain weighing about 1400 grams has a corpus callo- 
sum of about 6 square centimeters area. These are extreme instances, 
