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Morphology of the cerebellar dentate nucleus in a chimpanzee.

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Morphology of the Cerebellar Dentate Nucleus
in a Chimpanzee
T h e University of O k l a h o m a Medical Center, O k l a h o m a City, O k l a h o m a
Recent contributions to our knowledge
in the field of neurophysiology of the cerebellum have stimulated additional morphological studies. Evidence suggesting that
the cerebellar nuclei function in more than
a simple relay capacity draws added attention to their structure. The large size of
the dentate nucleus in man with its thin
lamina, discrete borders and extensive convolutions must be associated with unique
features of cerebellar function. This specific organization of the dentate nucleus is
a characteristic feature in the anthropoid
apes and man. In some of the subprimates
the dentate nucleus shows a tendency toward lamination and folding. However,
the lamina is wide with rather poorly defined borders and the outer contour exhibits only broad, gentle undulations. A
shallow hilar region may be present. In
lower primates, e.g., the macaque monkey,
the dentate nucleus also has a simple form.
Wax model reconstructions of the cerebellar nuclei of the macaque exhibit a definite
hilus in the dentate nucleus opening ventromedially and superiorly. The outer contour is smoothly curved with one broad,
shallow sulcus on the dorsolateral surface
near the inferior extremity of the nucleus.
The emboliform nucleus is rather broadly
continuous with the inferior portion of the
dentate nucleus. The gray lamina is broad
and irregular in thickness. In the gibbon
(Tilney, ' 2 8 ) the dentate nucleus shows
more of the features characteristic of its
configuration in the higher primates. The
nucleus has a number of well-defined plications especially along the lateral wall. In
the latter region the lamina is thinner and
the borders are more distinct than elsewhere. The dentate nucleus in the orangutan, chimpanzee and gorilla exhibit a
marked difference from that in the lower
species and great similarity to the human
nucleus. Tilney ('28) presents photographs of stained sections through the
dentate nucleus in these three species. The
appearance of this nucleus in sections,
especially in the chimpanzee and gorilla is
remarkably like that in the human. The
lamina is thin with well defined borders,
extensively folded into furrows and ridges
over the entire nucleus. A well defined
hilus is visible in appropriate sections.
The great similarity of the dentate nucleus in the higher primates and man indicate that studies of these anthropoid
species would aid in the understanding of
this nucleus in man. There is a paucity of
morphological data on the primate cerebellar nuclei. The value of quantitative data
in neuroanatomical investigations is becoming more apparent. These factors led
to this study of the morphology and volume
determination of the dentate nuclear in a
chimpanzee specimen that we obtained.
The study is based upon a specimen obtained through the courtesy of the Oklahoma City Zoo. This adult, female animal
had been in the zoo for several years and
becoming somewhat vicious, was killed.
The exact weight and age are unknown.
The brain was removed a few hours after
death and submerged, intact, in 10% formalin. Eleven months later the brain
weighed 349 gm and had these measurements: greatest width, 91 mm; frontal to
occipital poles, 106 mm; basal surface of
temporal lobe to vertex, 61 mm. No abnormalities were noted then or in subsequent studies.
The infratentorial brain stem, including
the cerebellum, was removed by a transverse cut at the level of the inferior colliculus. The cerebellar cortex and underlying white matter was cut away as ex81
tensively as possible without cutting into are those customarily used in describing
the cerebellar nuclei. This reduced block the infratentorial brain stem. Thus, for
of brain stem was then embedded in paraf- the cerebellar nuclei the terms dorsal-venfin using the ethyl alcohol-xylol technique. tral and superior-inferior denote axial lines
The block of tissue was cut into serial sec- parallel with these same axes as applied
tions at 15 in a transverse plane at right to the medulla and pons. The superior-inangles with the longitudinal axis of the ferior axis through the cerebellar nuclei
will be considered as a line parallel with
infr atentorial brain stem.
For this study every fifth section the floor of the fourth ventricle. A section
throughout the extent of the cerebellar cut in a plane at right angles to the supenuclei was stained using the luxol fast rior-inferior axis is a transverse section of
blue-cresyl violet procedure (Kluver and the cerebellar nuclei. A section cut in a
Barrera, ’53). Photographs were made of plane at right angles to the dorsal-ventral
every tenth section at a magnification of axis will be considered as a frontal section
of these nuclei (discussion on p. 89).
18 diameters.
Configuration. The following descripA wax plate model of the right dentate
nucleus was reconstructed from the photo- tion is based upon study of both the wax
graphs utilizing midsagittal structures and model reconstruction and the stained serial
the floor of the fourth ventricle as guide sections. The substantia grisea of which
the dentate nucleus is composed is arplanes for orientation.
The volume of the dentate nucleus was ranged in a thin lamina which is disposed
determined in the following manner. First, in rather definitely patterned gyral-like
the limiting boundary of the nuclear mate- folds. Furthermore, this folded lamina is
rial as seen in the photographs was care- grossly fashioned as the cortex of an irfully outlined with the aid of microscopic regular, incomplete spheroid. Thus, the
reference to the stained sections. The area dentate nucleus has external and internal
occupied by the nuclear material, so out- surfaces. These surfaces become continlined, was measured with a planimeter. uous at the lip-like border of a hilar region.
Five readings were made of each section The white matter which occupies the inand the average value determined. The terior of this spheroid is continuous
area measurements of each section were through the hilus with the general white
then plotted to scale on a line graph and matter of the corpus medullare and in no
the volume determined by the method of gross respect differs from it.
planimetric measurement of the “area unThe dentate nucleus is considerably flatder the graph.” Since these measurements tened along a dorsolateral-ventromedial
and graph plotting were done at a magni- axis. Due to the position of the hilus this
fication of 18 the volume reading was re- flattening is more pronounced dorsally so
duced by 183to natural size value.
three surfaces can be described, viz., dorThe average width of the lamina of gray solateral, ventral and ventromedial (fig.
matter comprising the nucleus was deter- 5). Correspondingly, three borders exist;
mined from the stained sections by using a dorsomedial, ventrolateral and ventromedcalibrated ocular micrometer. This infor- ial. These surfaces and borders converge
mation together with the volume made pos- dorsoinferiorly to produce an inferior pole.
sible an estimation of the surface area.
There is only a slight degree of tapering
superiorly so the nucleus also exhibits a
superior border (figs. 1, 2).
Planes and axes of reference. The folThe large hilar orifice opens onto the
lowing statements are necessitated by vari- superior and dorsal half of the ventromedations found in the literature in regard to ial surfaces (figs. 2, 3 ) . This opening is
the nomenclature of planes and axes of somewhat triangular in shape so that its
reference pertaining to the cerebellar nu- borders constitute superior, dorsal and
clei. Since the cerebellar nuclei lie in the ventral lips (fig. 4 ) . The superior lip,
corpus medullare of the cerebellum dorsal which is also the superior border of the
and dorsolateral to the fourth ventricle, nucleus, is somewhat J-shaped as viewed
the most satisfactory positional references from the superior aspect on the left side
or as a reversed J on the right side. The
long arm of the J is the superior border
of the dorsolateral surface while the curved
portion is the same border of the ventral
and ventromedial surfaces of the nucleus
(fig. 3 ) . The dorsal lip of the hilus presents a very distinct, straight line extending
inferiorly from the dorsal limit of the
superior lip nearly to the inferior pole.
This line is approximately parallel with
both the sagittal axis and the floor of the
fourth ventricle. The ventral lip of the
hilus presents a jagged line extending
obliquely from the ventromedial limit of
the superior lip nearly to the inferior pole
(figs. 2, 3, 4). These three lips (viz., superior, dorsal and ventral) circumscribe the
hilar region and are roughly disposed as
the sides of a right triangle with the ventral lip forming the hypotenuse.
The dorsolateral surface of the dentate
nucleus is bounded by the dorsomedial, superior and ventrolateral borders (fig. 1 ).
The dorsomedial border coincides with the
dorsal lip of the hilus in the superior two
thirds of the nucleus (fig. 4). The superior
border is rather straight and nearly parallel
with the dorsal-ventral axis. The ventrolateral border forms an arched line from
the ventrolateral portion of the superior
border to the dorsally placed inferior pole.
The greatest width of the dorsolateral surface is about one-fourth of the length of
the nucleus from the superior border (fig.
1). The most characteristc feature of the
dorsolateral surf ace is the orderly arrangement of gyri. The gyri consist of relatively
straight, continuous, parallel longitudinal
ridges extending inferiorly from the superior border. In the inferior and lateral por-
Fig. 1 Photograph of a wax model reconstruction of the right dentate nucleus in the
chimpanzee. Dorsolateral surface. See figure 5A for aspect of orientation.
Fig. 2 Photograph of the ventromedial aspect of the same model as shown in figure 1.
See figure 5A for aspect of orientation. A, B, C, levels of transverse sections shown in figure 5.
tion of the dorsolateral surface there is a
slight ventral deviation of the gyri. The
dorsally placed gyri are considerably narrower than those in the ventral portion.
Furthermore, the gyri, particularly the
more ventral ones, are narrower superiorly
becoming broader as they extend inferiorly.
It follows, that the dorsal and superior portion may be designated as a microgyric
area as will be discussed later. Correspondingly, the more ventral and inferior portion
may be called the macrogyric area. However, it is apparent from the model and
sections that the transition is gradual and
no sharp line of demarcation between these
areas is indicated. On this surface there
are a few deep sulci with several shallow
ones intervening. The latter are especially
numerous in the dorsomedial portion of
the nucleus.
The ventral surface of the dentate nucleus is considerably smaller than the dorsolateral surface. Superiorly it is broad
and rather sharply demarcated by ventrolateral and ventromedial borders from the
dorsolateral and ventromedial surf aces respectively (fig. 5 A ) . Inferiorly the ventral
surface is much narrower and rounded so
that these limiting borders are very indistinct (fig. 5C). Thus, in the inferior
half of the nucleus the ventral surface
merely constitutes a rounded area of continuity from the dorsolateral to the ventromedial surfaces. The gyral pattern on this
surface will be described later.
The ventromedial aspect of the dentate
nucleus (fig. 2 ) presents the same contour
and limiting borders as the dorsolateral,
viz., relatively straight dorsomedial and
superior borders and a curve semicircular
Fig. 3
Superior-medial aspect of the same model as shown in figure 1.
ventral border. This area is divided into
two, approximately equal subdivisions.
First, a large superior and dorsal right
triangular area which constitutes the hilar
orifice and which has already been described. Second, a ventral and inferior region which makes up the medial portion
of the nucleus. Within the hilar area, as
can be seen on the model, is presented the
inner surface of the dorsolateral portion of
the nucleus. This exhibits a gyral and
sulcal pattern which is the reciprocal of
that seen on the dorsolateral aspect. Ventral to the ventral hilar lip the concavity of
the nucleus presents a ventrolateral and
inferior recess (fig. 3 ) . The medial portion of the nucleus is bounded dorsally by
the jagged, diagonally directed, ventral
lip of the hilar orifice. This portion of the
nucleus is continued ventrolaterally from
the ventral lip to the ventromedial border
where it becomes continuous with the ventral surface. The gyri on the ventral and
ventromedial surfaces are, for the most
part, continuations of the gyri on the dorsolateral surface. The more dorsal gyri on
the latter surface are continuous around
the inferior pole onto the ventromedial surface u p to the ventral hilar lip. The ventral deviation of the larger, ventral gyri on
the dorsolateral surface as they are followed inferiorly, represent the beginning
of a long spiral pattern as these gyri extend onto the ventral and ventromedial
surfaces. This is more readily noted if the
sulcal pattern is followed. On the ventromedial surface these gyri become largely
effaced by flattening. The sulci thus be-
,,.. .....- .._.
Fig. 4 Outline drawing of figure 2. Ventromedial aspect of right dentate nucleus showing
boundaries of the hilus. Emb.. aortion of the emboliform nucleus that is continuous, in
transverse sections, with the dentate nucleus. Dotted line marks site of continuity of emboliform and dentate nuclei.
come less marked and come closer together
in the inferior half of the ventral hilar lip
(fig. 2 ) .
Orientation with reference to brain stem
axes. The dorsomedial border of the dentate nucleus is a rather stable landmark
for orientation. It is approximately a
straight line and maintains, from its superior to inferior extent, a fairly constant
distance of 5.5 mm from the midsagittal
plane. This border also maintains a fairly
constant relation to the floor of the fourth
ventricle, there being only a slight dorsal
deviation in this plane from superior to
inferior. In the central region this dorsomedial border is about 8.5 mm dorsal to
the level of the floor of the ventricle. The
dorsolateral surface is slightly convex dorsolaterally but in general lies in a plane
which forms an angle of approximately
30" with the transverse axis (fig. 5). This
surface deviates slightly laterally from its
superior toward its inferior extent. The
orientation of the ventromedial surface is
difficult to define due to the large hilar area
and a marked lateral deviation from superior to inferior. However, a favorable view
of this surface of the nucleus was taken
from an aspect of about 20" ventral from
the transverse axis (figs. 2, 5).
Continuity o f the dentate and ernboliform nuclei. The emboliform nucleus is
a flat lamina of gray matter disposed
roughly in a parasagittal plane, its dorsal
margin being somewhat medial to its ventral margin. This nucleus occupies a portion of the hilar region. It is separated
from the dentate nucleus except for its
most inferior portion. The dorsal margin
of the emboliform nucleus is parallel and
in close relationship with the dorsomedial
border of the dentate nucleus (fig. 5B).
On the inferior one-third of the dentate
nucleus the dorsomedial border presents a
short hook-like extension ventralward (figs.
5B, 2, 3 ) . Thus, in this region the dorsal
lip of the hilus does not exactly coincide
with the dorsomedial border of the nu-
Fig. 5 Outline drawings of transverse sections of the dentate nucleus at levels marked
A, B and C on figure 2. E, emboliform nucleus; J, site of junction of emboliform and dentate nuclei.
cleus. In the inferior one-fourth of the nucleus the free edge of this hook-like process is fused with the dorsal margin of the
emboliform nucleus. The site and extent
of this continuity is indicated by the dotted
line on figure 4. Only this attached portion
of the emboliform nucleus was included in
the wax model. The ventral margin of the
reconstructed portion of the emboliform
nucleus is separated from the ventral hilar
Lip by a narrow slit (0.2 mm). This relationship is maintained inferiorly. Since
the inferior lip extends dorsoinferiorly, the
emboliform nucleus in this region, and
from this aspect, is triangular in shape
with an apex near the inferior pole. The
fusion of this inferior triangular portion
of the emboliform with the dentate nucleus is so complete that decision on a
site of junction is quite arbitrary. An attempt to identify a sharp line of junction
between these nuclei on the basis of neuronal cell types and cell distribution was
unsuccessful. Thus, these two nuclei are
fused in a histologically continuous manner and the described line of fusion is
made solely on a gross topographical basis.
Linear dimensions. The following dimensions were determined from the wax
model but given here as converted to
natural size. Measurements made along
various axes are given in table 1. The
superior-inferior extent is 10.7 mm. The
width and height as measured along lines
parallel to the transverse and dorsal-ventral axes of the brain stem are 8.3 and 7.2
mm, respectively. A better concept of the
size of the nucleus is gained from measurements made along axes intrinsic to the
dentate nucleus. Here the superior-inferior
extent is as given above since the longitudinal axis of the nucleus is almost exactly in the longitudinal axis of the brain
stem. The distance from the dorsomedial
to the ventrolateral borders of the nucleus
at their greatest separation is 9.4 mm.
What may be designated as the width of
the nucleus, i.e., from the ventromedial to
the dorsolateral surface, varies considerably. At level A in figure 2, where this
dimension is greatest, it is 6.4 mm, while
at level C in the same figure it is 3.3 mm.
Linear dimensions of the hilar orifice as
measured along straight lines are as follows: from the dorsal lip to the ventral lip
at the superior border, 6.0 mm; from the
superior border to the inferior extent of
the hilus along the dorsal lip, 8.5 mm;
from the superior border to the inferior extent of the hilus along the ventral lip,
10.5 mm.
Thickness of the dentate nuclear lamina.
Measurements were made of the thickness
of the dentate nuclear lamina on the
stained sections with a calibrated ocular
micrometer. Certain factors effect the accuracy of the measurements. First, under
microscopic examination it is difficult to
define a sharp line of junction between the
nucleus and the surrounding white matter.
Also, the type and differentiation of the
stain effect the definition of this border.
The undulating contour of the dentate nucleus allows for a great deal of tangential
sectioning. Natural variations in the thickness of the lamina appear to occur. Upon
consideration of these factors sample regions were carefully selected and the thickness measured. The average of 65 measurements is 0.16 mm, with a range from
0.11 to 0.20 mm.
Volume. The procedure for determining the volume of the gray matter constituting this nucleus is given on page 82.
The value obtained is 84.76 mm3. It is to
be noted that this is the volume of the
nuclear gray matter and does not include
the white matter which occupies the concavity of the dentate field.
Surface area. Since the thickness of
the dentate lamina is fairly uniform over
the entire nucleus both on the surface of
the gyri and in the sulci it appears that a
reasonable value for the outer surface area
is the quotient of the volume divided by
the thickness of the nuclear lamina. This
results in a value of 547 mma. Due to the
large relative size of the dentate nucleus
Comparison of Zineat measurements of the dentate nucleus
(Fowler, '01 )
(Jakob, '28 )
In superior-inferioraxis
In transverse axis of brain stem
In dorsal-ventral axis of brain stem
Dorsomedial to ventrolateral borders;
greatest extent
Dorsolateral to ventromedial surf aces
in contrast to the thickness of the lamina
the inner surface must have approximately
the same area.
Planes and axes o f reference. In comparing the topography of cerebellar nuclei
of various specimens or species solely from
microscopic sections, it is important that
the exact planes and axes of reference be
understood. Confusion exists particularly
with reference to man and other primates
where the longitudinal axis of the infratentorial brain stem deviates markedly
from the cerebral fronto-occipital axis.
Published figures illustrate that sections of
cerebellar nuclei have been made, named
and described without making clear two
differing positional points of reference.
First, the cerebellar nuclei may be oriented
and sectioned with respect to the longitudinal axis of the infratentorial brain stem.
Here the terms of transverse and frontal
(or horizontal) are readily understood as
being at right angles with each other.
Other figures have been described where
the nuclei have been sectioned in conjunction with the entire brain. In these circumstances the orientation of the plane of
sectioning is described with reference to
the axes of the cerebrum. Here, sections
made in a plane at right angles to the cerebral fronto-occipital axis are designated as
transverse or frontal. In this case, when
serial sectioning is continued occipitalward
the cerebellum and brain stem are sectioned in an oblique fashion. Consequently, in such sections through the dentate nucleus, what is frequently described
as dorsal and ventral is more accurately,
dorso-superior and ventro-inferior. Thus,
in descriptions of the cerebellar nuclei the
planes and axes of reference need to be
explicitly defined. Orientation of these nuclei on the basis of infratentorial brain
stem axes is preferred.
Comparison with published data on the
chimpanzee and other anthropoid apes.
The weight of the brain described herein
as being 349 gm is apparently within the
normal range for the adult female chimpanzee. Parker (1880) refers to data on
4, presumably adult specimens with
weights of 285,376,312 and 397 gm. The
first two listed were females, the sex of
the others was not given. Tilney ('28)
used a brain weighing 350 gm for his
study. This latter specimen had transverse
and longitudinal dimensions of 88 and 190
mm, respectively. The specimen described
here had a width of 91 mm and measured
106 mm from frontal to occipital poles.
It is possible that the longer length given
by Tilney was measured from the frontal
pole to the caudal end of the medulla.
We are not aware that figures of model
reconstructions or detailed descriptions of
the dentate nucleus in the chimpanzee or
other anthropoid apes have been published.
Tilney ('28) presents photographs of several transverse sections through the cerebellar nuclear area of the chimpanzee,
orang-utan and gorilla. However, his description of the dentate nucleus is very
brief and limited to the shape of the nucleus in individual sections.
Comparison with published data on the
human dentate nucleus. As far as is
known there are figures of only two reconstructed models of the human dentate nucleus in the literature. Kappers, Huber and
Crosby ('36, p. 795) present two photographs of a wax model reconstruction of an
adult human dentate nucleus. The description of the model is limited to the following: "The human nucleus dentatus is a
sac-like structure, the opening of which
is directed medialward and frontalward.
The lamellation of the mass is such that
the furrows lie in the longitudinal axis of
the nervous system." No measurements
are given. However, the photographs are
very illuminating for purposes of this comparison. Allowing for the fact that their
model was of the left while the one described here is of the right nucleus the two
views presented of the human dentate nucleus are strikingly similar to figures 1
and 2 of the chimpanzee nucleus. The
limiting contours are almost identical. The
gyral pattern differs only slightly. On the
dorsolateral surface the gyri in man appear
to extend in straight superior-inferior axes.
In the chimpanzee these deviate slightly
ventrally from superior to inferior and
form a long spiral around the ventral and
onto the ventromedial surfaces. The tendency for the gyri to flatten and the suki to
approach each other in the inferior portion
of the ventromedial surface is very similar
in both models. The terminology used in
their publication is somewhat confusing.
The photographs are designated as medial
and lateral views of the nucleus yet the
tops and bottoms of the figures are labeled
medial and lateral. It is possible that their
figures were taken, as ours, from dorsolateral and ventromedial aspects. This
would suggest their borders to be, more
exactly, dorsomedial and ventrolateral.
The other model of the dentate nucleus
found in the literature is presented by
Fowler ('01). It was constructed from serial sections of a human new born. Six
photographs of the model are given. This,
too, is remarkably similar to the chimpanzee model. The gyral configuration is
almost identical with the model presented
here, exhibiting a longitudinal pattern with
the same slight ventral deviation in the
inferior and lateral portion of the dorsolateral surface. Also, his description of
major and minor sulci on this surface corresponds very closely with that in the
chimpanzee. The shape and extent of the
hilar orifice is very similar in all three
models. The chimpanzee and the Kappers,
Huber and Crosby models present a slightly
more pronounced inferior pole than shown
in the newborn specimen.
Demo16 ('27) describes the gyri of the
dorsal surface of the human dentate nucleus as being smaller, more sharply defined and more regular in arrangement
than those in the ventral portion. He then
divides the dentate nucleus into two territories, a microgyric, dorsomedially and a
macrogyric, ventrolaterally. In the chimpanzee model this distinction can be made
with the following qualifications. The
smaller and more regularly arranged gyri
occupy the superior as well as the dorsomedial portion. The larger, more irregular,
and on the medial surface more flattened
gyri are located inferiorly, ventrolaterally
and ventral to the hilus on the medial surface. Also, as has been previously stated,
the junction between these two territories
is indistinct, there being a gradual transition between the two areas. A somewhat
similar division of the nucleus in man has
been made on the basis of staining reaction
(Gans, '24) and neuronal cell types and
their distribution (Hassler, '50). Hassler
describes a sharp line of junction between
the superior dorsomedial magnocellular
and the inferior ventrolateral parvocellular portions. In a preliminary microscopic
study of this specimen we have been unable to define such a sharp line of junction in the chimpanzee. Consequently, we
are unable to closely correlate any histological division with the gross topography
of the nucleus.
The continuity of the emboliform and
dentate nuclei existing in the chimpanzee
is also described for the human. However,
the exact site and extent of this junction
is not clearly defined. Jakob ('28) states
that in many places the emboliform is continuous with the dorsomedial portion of the
dentate nucleus. In referring to this fusion
DBjkrine ('01) considers the emboliform
as an accessory dentate nucleus due to its
intimate continuity with the dentate nucleus. He described this fusion as occurring in the inferior portion of the latter. In
the chimpanzee the only region where the
dentate and emboliform nuclei are continuous is in the inferior one-fourth of the
hilar area and, as in man, in the dorsomedial portion. As can be judged from
photographs of the two human models
(Kappers, Huber and Crosby, '36; and
Fowler, '01) the dentate and emboliform
nuclei may be approximated in a manner
very similar to that in the chimpanzee.
However, Kappers, Huber and Crosby state
that the emboliform nucleus is connected
at several levels with the dentate nucleus.
Fowler ('01) does not describe a confluence of these two nuclei in the human newborn.
A comparison of the linear measurements of the dentate nucleus in the chimpanzee, the newborn human and the adult
human may be made from the data in
table 1. The length of the nucleus in the
superior-inferior axis and the greatest distance between the dorsomedial and ventrolateral borders are approximately equal in
the chimpanzee and the human newborn.
The distance between the dorsolateral and
ventromedial surfaces of the nucleus, as
given for the newborn, falls within the
range of this measurement in the chimpanzee. The only available linear measurements of the adult human dentate nucleus
have been made along lines parallel with
the three major axes of the brain stem.
In comparing such linear dimensions of J. S. Little) working in our laboratory usthe chimpanzee with that of the adult hu- ing the same procedure determined the
man the following relationships are noted. volume of the dentate nucleus in one newIn the transverse axis measurements born and three adult human specimens.
are about equal. In the dorsal-ventral The ages of the adult specimens were unaxis the figure for the chimpanzee is just known. The values obtained were 71 mm3
within the lower limit of the range of varia- for the newborn, 124 and 190 mm3for two
tion given for man. In the superior-infe- adults. Separate measurements and calcurior axis the length in the chimpanzee is
only 57% of that in man. Thus, the lations of the third adult specimen were
principal, linear dimensional, difference made by each student. Their independent
between the dentate nuclei of the chim- values were 220 and 241 mm'. This inpanzee and of the adult human is the con- formation indicates that the volume of the
dentate nucleus in the adult chimpanzee
siderably greater length in man.
DCjCrine ('01) gives the following di- is equal to or slightly greater than that in
mensions of the hilus in the adult human the newborn human. It further shows that
dentate nucleus: height, 5-7 mm; length, the volume of the dentate nuclear gray
10-12 mm. The reference points used for matter is much greater in the adult human
making these measurements are not given. than in the chimpanzee. In the latter
In the chimpanzee a straight line between species it is only about 55% of the averthe dorsal and ventral hilar lips at the age figure given for man. This difference
superior border measures 6.0 mm. This in volume can perhaps be accounted for
falls within the range for the height as by the greater length of the nucleus and
given by D6jCrine. The length as given greater thickness of the dentate nuclear
for the adult human nucleus (10-12 mm) lamina in the adult human.
probably should be compared with the
measurement made in the chimpanzee
model reconstruction of the denfrom the superior border to the inferior
extent of the hilus along the dorsal lip tate nucleus in an adult female chimpan(8.5 mm). This greater length of the hilus zee was made from serial sections. Using
in man is associated with the greater the model and the stained serial sections
length of the entire nucleus in this same the following morphological information
was obtained.
1. The gray matter comprising the nuThe thickness of the dentate nuclear
lamina in man is frequently given as 0.3 cleus is arranged as a thin lamina which
to 0.5 mm (e.g., Jansen and Brodal, '58). is disposed in gyral-like folds. This folded
The thickness of this lamina in the stained lamina is grossly fashioned as the cortex
sections of the chimpanzee varies from of an irregular incomplete spheroid with
0.11 to 0.20 mm. There is therefore a con- an open hilus. The hilus opens superiorly
siderable difference between the two spe- and ventromedially and is bounded by
cies, probably greater than could be ac- superior, dorsal and ventral hilar lips. The
counted for by differences in fixation and nucleus is flattened along a dorsolateralother variances in histological technique. ventromedial axis.
2. The longitudinal axis of the nucleus
As far as is known there has been only
one other study made of the volume of the is nearly parallel with the same axis of
dentate nucleus. Hopker ('51) gives the the brain stem. The dorsolateral surface
volume determinations for both right and lies in a plane which forms an angle of
left dentate nuclei in 27 human brains. approximately 30" with the transverse
The values given for the right nucleus axis.
range from 74 to 212 mm3, the average
3. The gyri on the dorsolateral surface
being 155 mm3. This is to be compared are arranged as parallel ridges in the
with the value of 84.76 mm3 for the chim- longitudinal axis. They extend inferiorly
panzee nucleus. The procedure for deter- from the superior border and continue
mining the volume was very similar in around onto the ventral and ventromedial
both cases. Two students (V. Robards and surfaces. Dorsomedially and superiorly
the gyri are narrower than elsewhere thus
constituting a microgyral area.
4. There is a fusion of the dorsal margin
of the emboliform nucleus with the inferior one-fourth of the dorsomedial portion of the dentate nucleus.
5. The following quantitative values are
recorded. Linear dimensions of the dentate
nucleus are: in the longitudinal axis, 10.7
mm; from the dorsomedial to the ventrolateral borders at their greatest separation,
9.4 mm; between the dorsolateral and
ventromedial surfaces, 3.3 to 6.4 mm. The
average thickness of the dentate nuclear
lamina is 0.16 mm. The volume of the
nuclear gray matter is 84.76 mm3. The
calculated value of the area of the outer
surface of the dentate nucleus is 547
A comparison of the dentate nucleus in
the chimpanzee and in man led to the following conclusions.
1. As judged from wax model reconstructions the shape of the dentate nucleus
in the chimpanzee is very similar to that
in man.
2. The size, direction and general configuration of the gyral pattern is remarkably alike in both species.
3. The shape, position and boundaries
of the hilar region are nearly identical.
However, the length of the hilus in the
chimpanzee is less than in man.
4. The greatest linear extent of the
dentate nucleus in the transverse axis is
approximately equal in the two species.
In the dorsal-ventral axis the measurement
in the chimpanzee is just within the lower
limit of the range given for man. In the
superior-inferior axis the length of the
dentate nucleus in the human 1s consider-
ably greater than the corresponding dimension in the chimpanzee.
5. Continuity of the dentate and emboliform nuclei occurs in both species.
6. In the chimpanzee the thickness of
the dentate nuclear lamina is less than half
the thickness of this lamina in man.
7. The volume of the dentate nuclear
gray matter in the chimpanzee is approximately 55% of the average value given for
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Man. Macmillan Co., N. Y.
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morphology, cerebellar, chimpanzee, dentate, nucleus
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