388 Some Racial Peculiarities of the Negro Brain 
TABLE VIa. 
RELATION OF THE AVERAGES OF THE AREAS OF THE ANTERIOR TO THE POSTERIOR 
LINEAL HALF OF THE CorPUS CALLOSUM. 
No. of 
Beatin Anterior. Posterior. Ratio. 
sq. cm. sq. cm. 
Caucasiangemalleammaocicdsiete 42 3.70 3.04 122 : 100 
INGPTOSMale armen coe crsn ket 62 3.06 3.02 101 : 100 
Caucasian wfemalewenn.o..ceece 9 Oeil 2.87 110 : 100 
Negro: femaletrayaceoscccciece 25 2.86 2.86 100 : 100 
Each end of the corpus callosum is larger in the Caucasian male than 
in the Negro male or in the others. Likewise the Caucasian female is 
larger than the Negro female, the anterior end is larger than the Negro 
male, the posterior end being smaller than the Negro male and about 
the same size as the Negro female. The anterior end of the corpus callo- 
sum is small in the Negro male, and smaller in the Negro female. It is 
large in the Caucasian female and larger in the Caucasian male. The 
posterior end is about the same size in each sex, but smaller in the female 
than in the male, so that the anterior end shows a racial and sexual dif- 
ference, while the posterior end shows a sexual difference only. This can 
be located more definitely than in the two lineal halves of the corpus cal- 
losum. Comparing the genu and the splenium, leaving aside the inter- 
mediate portion of the corpus callosum, a distinct racial difference is 
found similar to that just discussed. Chart VII taken from Table VII 
gives a graphic picture of the essential differences, which are about the 
same as those found in Chart VI. To prepare this chart, the corpus 
callosum is divided into four parts, six-tenths (.6) anteriorly being sep- 
arated from four-tenths (.4) posteriorly, and each of these two parts be- 
ing divided in half. This is done by using lines perpendicular to the 
brain axis, and parallel to lines used in preparing for measurements for 
Table VI. This gives the splenium two-tenths of the total lineal length 
of the corpus callosum anterior to the splenium a narrow part, which 
I call the isthmus, two-tenths of the total length; anterior to this the 
body, three-tenths of the total length. These divisions are shown in 
Figures 92 and 9». Several brains are broken through the fissure of Ro- 
lando and the break invariably passes through the isthmus. The conclu- 
sion is that the body of the corpus callosum contains the fibers connecting 
the motor areas of the two hemispheres, and the isthmus and splenium 
contain the fibers connecting the sensory areas of the two hemispheres, 
and all areas posterior to these. Eliminating the isthmus and body must 
leave the fibers that more definitely connect the association centers and 
