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Volumetric determinations of the parts of the brain in a human fetus 156 mm. long (crown-rump)

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VOLUMETRIC DETERMINATIONS OF THE PARTS O F
THE BRAIN I N A HUMAN FETUS 156 MM.
LONG (CROWN-RUMP)
F. C. DOCKERAY
Department of Psychology, University of Kansas
I n the present communication there is reported a study of the
volume of the main divisions of t,he brain as they are found in a
fetus about four months old. The work was undertaken as a
step in the history of the growth of the individual parts of the
brain under the premise that a knowledge of their volume priority would indicate in a general way the functional priority of
these parts. By means of the wax-plate reconstruction method
it is possible to make an accurate enlarged model of the brain
that can be separated into its chief component parts. Since such
a model is made of wax of a uniform composition the relation
by volume and by weight of the different parts can be determined
both as to each other and as to the brain as a whole. This same
method was used in determining the volume of the different parts
of the opossum brain, by Professor Streeter and by Mr. H. A.
Tash, who reported their results at the meeting of the American
Association of Anatomists at 1thaca.I
The brain measured was taken from a male fetus measuring
156 mm. crown-rump, and 201 mm. total, length. The head
measurements were: Bitemporal, 48 mm. ; occipito-frontal, 58
mm. These measurements were made on the fresh specimen.
Its weight was 296 grams. The specimen was preserved in 10
per cent formalin, the skull having been opened to facilitate the
penetration of the fixative. Subsequently the brain was removed,
embedded in celloidin and prepared in serial sections 50 p thick,
1 Streeter, G. L., 1911, Volumetric analysis of the brain of the opossum.
Proc.
Amer. Assoc. Anat.; Anat. Rec., vol. 5 , p. 91.
207
THE ANATOYICAL R E C O R D , VOL.
9, N O . 2
208
F. C. DOCKERAY
every other section saved and stained with alum-cochineal.
From this series a model was made enlarged five diameters after
the well known Born method. Serial drawings were made with
n projection apparatus on papers which were then incorporated
in wax plates of such a thickness that the enlargement in all
plmes was the same ( x 5). The drawings were then cut out
from the plates and filed. This gave a model of the whole brain
with the ventricles removed.. The plates were then gone through
n second time and the various parts cut away from each other
so that their individual weights and volumes could be separately
determined. It was found that this could be done with considera,ble accuracy, and having the stained sections as a guide, it
would have been possible to have carried the subdivisions further.
But, having in mind both younger and older stages, it was decided that the adopted subdivision would prove most practical
in the end. The results are given in table 1. I n the first column
of the table is given the weight in grams of the whole model and
of its parts. In the second column is given the percentage of
the total weight formed by each part, which would hold true for
TABLE 1
-
MODEL WGT.
I S GMR.
I
'
PARTS
.
~~
..
PER CENT O F
TOTAL WGT.
Ilhombencephalon. , . . . . . . . . .
Medulla and pons.. . . . . . . . . . .'
Cerebellum.. . . . , . . . . . . . . . . . .
Mesencephalon. . . . . . . . . . . . . .;
Dicncephalon (inc. epiphysis)
Telencephalon. . . . . . . . . . .
Basal ganglia. . . . . . . . . . . .
Caudate nucleus (inc. parolf..
body and amygdaloid nu-
72,135
32.325
39.810
20.900
69.761
4.973
2.228
2.744
1.441
4 .so9
88.776
7.625
. . . . . . .. :
73.150
33.161
4.299
33.865
26.075
5.815
5.043
2.286
0.296
2.334
1.797
0.401
0.136
78.815
100.000
,
. . . . . . .'
Gtobus pallidus.. , . . , . . . . . . . . i
Archipallium. . , . , . . . . . . . . . . .
Fornix and hippocampus.. . . .
Paraterminal body.. . . . . . . . . . '
Olfactory bulbs.. .
Seopallium.. . . . . . , . . . . . . , , , . 1143.198
Total brain.. . . . . . . . . . . . . . . . . 1450.468
MODEL VOL.
I N CC.
-.
ACTD AI.
VOLUME
-_ _ ~ _
-~
___~
80.565
36.500
44 ,065
23.659
78.970
1457 ,658
125.210
0 644
0 292
0 352
0 189
0 631
11 661
1 001
82.805
37 ,538
4.867
38.341 ,
29.522
6.583 ,
2.236 ,
uY4.1Uu
1641.929
I
1
0 662
0 300
0 039
0.306
&
:
;
0.017
lU.64D
13.135
BRAIN OF A HUMAN FETUS
209
the actual brain just as for the model. In the third column is
given the volume in cubic centimeters of the whole model and
of its different parts. Instead of determining the volume of each
part separately it was found more practical to determine the
specific gravity of the wax plates and then calculate the volumes
from the weights given in the first column. In the last column
is given the volume of the brain itself and of its parts. This
was obtained by dividing the volume of the model by the amount
of the enlargement, i.e., the cube of five diameters. It is to be
remembered that this is the volume of the brain after it has been
embedded and prepared in serial sections. The volume of the
fresh brain could be obtained only by calculating the amount of
shrinkage the specimen experienced in this process.
The subdivisions that were used follow as far as possible the
embryological subdivisions adopted by His. Their boundaries
could in most cases be determined by the cell structure of the
sections. In some cases it was necessary to depend on the surface configuration of the model. The landmarks utilized in carrying out this subdivision are herewith detailed :
Rhombencephalon. This was separated from the spinal cord
as nearly as possible at a point post cephalic to the first cervical
nerve. The cephalic boundary was determined by a plane just
skirting the inferior colliculus and passing out ventrally just in
front of the pons. Laterally this plane passes just in front of
the brachium connecting the cerebellum and pons.
Cerebellum. This is plainly demarcated by its surface outline,
while the pons is determined more by its internal structure, the
main characteristic being the densely massed nuclei. The cerebellum at this time consists of a well fissured vermis and the two
lateral lobes which are fissured dorsally but are still smooth ventrally. In removing it the floccular margin was included and
also the brachium pontis on each side to the point at which it
meets the pons. The removal of the Cerebellum leaves the
medulla and pons, whose weight and volume are given together.
Mesencephalon. The caudal limit of the mesencephalon is the
same as the plane marking the cephalic border of the rhombencephalon, which has already been given. Its cephalic limit is a
210
F. C. DOCKERAY
wedge-shaped plane that projects in between the masses of the
diencephalon. At the median line its boundary is marked dorsally by the posterior commissure and ventrally by a point post
caudal to the mammilary bodies. From this median line the
plane of division on each side extends backward so as to include
the red nucleus with the midbrain and comes to the surface a t a
groove marking the antero-lateral margin of the superior colliculus. Owing to the advanced development of the colliculi and
the retarded development of the peduncular portion, the mesencephalon is V-shaped as regards its ventral aspect, as well as its
cephalic boundary.
Diencephalon. Its separation from the mesencephalon we have
already indicated. From the telencephalon it is separated bilaterally by the internal capsule, and a sharp line of demarcation on
the surface is afforded by the stria terminalis. Ventrally where
this is not present the line of division is continued along the anterior margin of the optic tract. By this manner of subdivision
there is comprised in this portion the optic tract and thalamus
including the habenular nuclei and epiphysis and also the whole
hypothalamus with the exception of the hypophysis, which had
been removed.
Telencephalon. This includes all the remainder of the brain.
It was subdivided into three main divisions as follows:
Basai ganglia. At the end of the fourth month these structures
are clearly defined and bear a relation that closely approxjmates
the adult. The putamen and globus pallidus are easily recognized in transverse sections. As for the lamina of capsule fibers
that surround them, the incisions were made half-way, so that
part of the fibers would go with the globus pallidus and part
with the caudate nucleus. The caudate nucleus throughout its
greater extent is likewise clearly defined. At its head and tail
ends, however, it is complicated by fusing with the parolfactory
body and amygdaloid nucleus respectively. On this account
these latter were included with it.
Archipallium. This includes, in the first place, the olfactory
bulbs, which were removed at a transverse line at the point where
BRAIN OF A HUMAN FETUS
211
they become free from the brain wall. This corresponds to both
the bulb and stalk of the adult. The paraterminal body includes
the gray substance where the olfactory bulb is attached and the
region of the future septum pallucidum and the pillar of the
fornix, which could not be easily separated from it. The remainder of the archipallium is made up of the body of the fornix and
its fimbricated extension into the hippocampus. The hippocampus is easily recognized by its histological structure and by the
way it bulges into the lateral ventricle. With i t was included
the dentate fascia and the uncinate body. The corpus callosuin
was included with the neopallium.
Neopallium. This includes the remainder of the telencephalon
and represents what we know in the adult as the convoluted cortex, together with the subjacent white matter and includes the
corpus callosum, as we have just pointed out.
I n conclusion I wish to acknowledge the courtesy of Professor
Streeter, who kindly put the resources of the Anatomical Laboratory of the University of Michigan at my disposal for the purpose of this investigation, and gave me many helpful suggestions
as the work progressed.
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