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Development of the cerebral sulci.

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DEVELOPMENT O F T H E CEREBRAL SULCI
C. J. CONXOLLY
The Catholic 17n.iZlersity of America, Washington, D . C.
EIGHT PLATES
( THIRTY-THREEFIQURES)
INTRODUCTION
Although much has been done on the study of the cerebral
sulci of the human brain, there is not yet complete agreement
as to the significance of certain sulci or how they should be
named. Considerable light, however, has been thrown on the
meaning of these furrows by the approach of comparative
anatomy, as, for example, in the calcarine region, and the
interpretations have been confirmed by fundamental histological studies. These latter investigations must always be
taken into account, but at the same time we should not overlook the established fact (Ariens Kappers, ’13) that a shift
occurs in the phylogenetic history of certain sulci relative to
the cortical areas and that they may be identified from their
external associations while histologically they no longer limit
precisely a cellular area which they may do in the lower primates.
Another approach to the interpretation of sulci is that of
their development. This matter of growth and development
is obviously one of prime importance, and the sequence of the
appearance of the sulci reveals gradual morphological differentiation and, we may assume, a physiological one.
In the earlier investigations in this field certain furrows on
the lateral and medial surfaces of the cerebral hemispheres of
fetal brains from the second to fourth month inclusive, were
described. They were regarded as true fissures or sulci which
later disappeared in whole or in part and hence were called
“transitory fissures.” They were later supplanted by permanent fissures.
113
114
C. J. CONNOLLY
The so-called transitory fissures were shown by Hochstetter
(1898) to be postmortem effects. The figures given by Retzius
(1896, Taf. I and 11)show such artificial furrows on the lateral
and medial surfaces; but that author later (’01) recognized
their true nature. They are also shown in the figures given by
Cunningham (1892, plates I, I1 and 111). Other investigators
such as Kollmann (’07) became convinced of the artificial
character of these furrows, and it may be considered as estalqlished that the “transitory fissures” on the lateral surface
and the so-called radial fissures on the medial surface are not
true sulci, but are postmortem effects and often due to the
fixation fluids. Cerebral hemispheres with smooth lateral surfaces up t o the fifth month are amply illustrated in the following study.
The evidence, however, was less clear as to whether any
true sulci were formed in whole or in part on the medial surface during these earlier months. His (1889) described an
arched furrow on the medial surface of the brain of the third
month. This “Bogenfurche” or fissura arcuata consists of an
anterior and a posterior part. The posterior is retained as
the fissure hippocampi. The anterior part is called the fissura
prima. It begins ventrally between the two divisions of the
olfactory brain and rises on the medial surface, causing an
invagination of the medial cerebral wall, as does the posterior
arcuata, and ends in front of the choroid fissure. It later becomes, according to His, the fissura parolfactoria posterior.
Hochstetter (1898) maintained that in well preserved specimens of the first 4 months of fetal life no arcuate fissure mas
to be seen, and that the described fissures were really postmortem effects. His, however, later (’04)reaffirmed in substance his earlier opinion based on a study of a third and
fourth month fetal brain. He describes further a sagittal
fissure coursing upward in front of the fissura prima and
passing over the middle portion of the fissura arcuata, and
called it the fissura arcuata accessoria. He recognized always
the radial furrows as artificial.
DEVELOPMENT O F THE CEREBRAL SULCI
115
Hines (’22) has made a thorough histological study of the
early stages of the brain and follows the development of the
hippocampal fissure from its earliest appearance, coming to
the conclusion that “The medial wall of the cerebral hemispheres of human embryos 16 mm. to 30 mm. in length is not
perfectly smooth. Its otherwise even contour is broken by a
shallow groove. The groove extends from the region of the
olfactory bulb to the tip of the temporal pole. It is the fissura
hippocampi or ‘Bogenfurche’ of His.”
Hochstetter (’24) insists, however, that the fissura arcuata,
including both its anterior part or fissura prima and its
posterior part or fissura hippocampi as described by His, is
a postmortem effect. He regards the fissura prima described
by Hines as the sulcus parolfactorius posterior and not the
fissura in the sense of His. He likewise speaks of the presence of a shallow furrow between the gyrus dentatus and the
gyrus hippocampi and calls it the sulcus hippocampi. This
sulcus never attains any great depth.
Of considerable morphological interest is the question
whether these fissures actually produce swellings on the vent,ricular wall of the hemispheres as His believed, and as the
term “complete ” fissures implied, or whether as Hochstetter
and others maintain, they are formed secondarily. Elliot
Smith (’31) observes that no fissure produces the hippocampus and in this sense emphatically states that “There is
no fissura hippocampi in the human brain.” The shallow
groove which is admittedly present might be termed the sulcus
hippocampi as Hochstetter suggested. The term fissura hippocampi, however, is now so uniformly used that it probably
will continue to be used in this modified sense.
MATERIAL
( a ) The HrdliEka collection
The fetal brains examined in this study are mainly from
the HrdliGka collection in the U. S. National Museum, Division
of Physical Anthropology.
116
C. J. CONNOLLY
On the occasion of Doctor HrdliEka's attainment of another
milestone in his long and distinguished career as scientist, it
is fitting to record here his splendid contribution to science in
making this collection. Throughout many of his earlier years
of activity, Doctor HrdliEka patiently accumulated a fine series
of mammalian brains including many of the wild animals of
the forest, and with meticulous care personally extracted the
brains. He further contributed to our knowledge by his experimentation with different preserving fluids, and placed his
results on record in a paper ('06) familiar to investigators.
The collection embraces a series of specimens extending from
the lower mammals to the human races including a considerable number of fetal brains.
The fetal brains of this collection which form the basis of
the present investigation consisted of twenty-five of Whites
and twenty of Negro and mixed-bloods. Some of the specimens, as might be expected in fetal material where pathological brains will naturally be met with, were not suitable for
satisfactory examination; but even in these cases some information could be gathered concerning the sulci in certain
cases in confirmation of observations made on the best
material.
The age of the fetal brains is not given for all specimens in
the records of the U. S. National Museum, and for some only
a rough approximation is recorded. Fortunately the body
lengths are given in many cases and from these one can arrive
at a closer approximation of the age. I n the younger specimens the stage of development of the cerebellum was also of
help in k i n g the age more precisely. The brain weight and
body weight are also recorded for several specimens.
The specimens were fixed in different percentages of formalin or of formalin and saturated or half-saturated solutions of
alum. The younger specimens were preserved in a mixture
of 43 parts water, 27 alcohol and 5 of formalin; the older
specimens in 52 parts water, 18 alcohol and 5 of formalin.
DEVELOPMENT O F THE CEREBRAL SULCI
117
( b ) Recelzt series
I n order to have a more complete series, with the age of the
specimens more precisely determined where such data was
wanting, the writer obtained during the past 2 years specimens from the hospitals of Washington, D. C. Some of these
were obtained at Providence Hospital and I wish to express
my thanks to the hospital staff for their kindness in preserving
the specimens. The greater number of recent additions were
obtained at Gallenger Hospital and I am especially indebted
to Dr. John Parks for his kindness in giving these specimens.
All the fetuses of this recent series were immediately placed
in 10% formafin by the hospital staff members, and generally
within a few hours I injected 10% formalin slowly into the
brain cavity on either side through the anterior fontanelle.
After a few days the brain was exposed but still left on the
cranial basis for measurement and other observations until
removed under the preserving fluid for closer examination.
A statement as to approximate age given at the hospital was
noted. The sitting height (C.R.) and foot length were then
taken and the approximate age determined from Streeter's
( '20) charts.
It is admitted by all investigators in this field that the C.R.
length and other single criteria are only approximations in
determining the age, as all structures tend to vary in size.
But combined data may give a close approximation and the
foot length, which is so easily measured, was found to be a
valuable aid in forming a judgment. I n the younger specimens up to and including the fourth month, the stage of development of the cerebellum was a further check on the age.
Some specimens were almost identical in C.R. length and in
foot length, and other characters fitted closely, thus confirming the age estimate. With the combined data checked by
Streeter's valuable charts, I feel that the age estimated for
specimens in the first half of fetal life is probably correct
within the limits of 1week. For all specimens data given by
h e y ('36) and Mall ('10) were consulted.
118
C. J. C O N N O L L Y
SIZE AND FORM O F BRAIN
I have added measurements on the brains of all age periods
which may prove useful. Length and breadth were taken in
the usual manner, but height here is the total projectional
height taken from the lower border of the temporal lobe to
the highest point on the median sagittal border, since it is not
practicable to take this measurement as is done in the adult
brain. Some further observations on the form of the brain
a t different periods will be noted.
The total number of brains examined was seventy. Out of
these I have based the study largely upon the best preserved
brains on which data existed so that the age could be estimated
approximately, and on which measurements could be taken.
This included practically all of the recent series (24) made
up mostly of young specimens (table 1 ) and a larger number
(27) from the U. S. National Museum representative of nearly
all age periods. For the second half of fetal life the study is
based solely on this latter series.
In the tables it is further stated whether the brain was that
of a White (W), Negro (N) or mixed-blood (M). Additional
data such as weigbt of body and weight of brain are given for
some specimens.
All the photographs are un-retouched and represent the
natural size of the brain at the different periods.
THE CEREBRAL HEMISPHERES
Third mowth. The smallest brain in the series is that of a
fetus with a C.R. length of 3.8 em. (Pr. 1, table 1). From the
development of the entire fetus and of the cerebellum in particular the age is estimated at about 10 weeks. Figure 1gives
a lateral view of the brain showing a quite smooth surface.
It is bean-shape in form with a depression containing the
lateral olfactory gyrus. Above this depression at a later stage
the sylvian depression forms. I n a specimen of similar size
from the U. S. National Museum (224844) there are wrinklings on the surface which are obviously postmortem effects
119
DEVELOPMENT O F THE CEREBRAL S U L C I
and illustrate what were formerly regarded as “transitory
fissures.”
Figure 2 shows the medial surface of the right hemisphere.
A prominent depression may be seen on the medial surface of
TABLE 1
CROWNNUMBER
RUMP
LENGTH
BPAIN
FOOT
AENGTH
.__
(C.R.)
cm.
Pr 1 w
G l w
G 2 w
G 3 w 9
P r
G
G
G
P r
2
4
5
6
3
w d
m c
m c
w E
w d
cm.
3.8
5.6
5.9
0.65
0.85
0.95
8.5
10.2
11.8
12.3
12.5
12.6
1.5
1.8
2.4
2.7
2.8
2.5
3rd month
10weeks
11 ”
11 ”
Ith month
13 weeks
14
15
16
16
16
”
”
”
”
”
2.8
G1Omc
G l l m c
G12m5
Pr4wd
G13mc
G14mc
G15mc
G16mc
13.0
13.4
13.6
13.6
13.7
13.8
14.2
16.8
17.0
17.0
17.2
2.8
2.9
3.0
3.4
3.1
3.4
3.3
3.8
4.0
3.8
5th month
1 7 weeks
17 ”
17 ”
17 ”
18 ”
18 ’’
18 ”
20 ”
20 ”
20 ”
20 ”
G17mc
G18mZ
G19m$
G20mc
17.2
18.2
18.8
21.5
4.3
4.2
4.4
5.4
6th month
2 1 weeks
21 ”
22 ”
24 ”
G 7m5
G 8 m c
G 9 m c
.-
-
Length
3resdth
Height
em.
em.
cm.
ILLUBTIWTIONS
~
_
_
Figs. 1& 2
1.4
1.2
2.0
2.1
1.6
1.75
0.95
1.5
1.7
3.0
3.0
4.0
4.4
4.35
4.4
2.6
2.55
3.5
3.7
3.8
3.7
2.4
2.2
2.8
3.O
3.1
3.0
4.5
4.6
4.8
5.6
5.0
5.5
5.7
5.4
5.7
6.1
6.4
4.1
4.1
4.2
3.9
4.0
4.7
4.7
4.6
4.8
4.8
5.4
3.2
3.2
3.3
3.2
3.2
3.6
3.8
3.4
4.1
4.0
4.1
Figs. 15 & 16
6.6
6.6
6.5
7.0
5.3
5.4
5.6
6.1
4.2
4.3
4.5
5.0
Figs. 22 85 23
Fig. 3
Fig. 8
Fig.10
Figs. 11& 1 2
Fig. 19
Fig. 20
the frontal lobe occupying a position similar to the accessory
arcuate of His. It is quite different in form from that on the
left hemisphere and hence is regarded as a postmortem effect.
Just caudal to the anterior olfactory lobe, the ventral surface
-
120
C. J. CONNOLLY
makes a sharp dorsal bend. On the medial surface there is a
shallow furrow confluent with it which in later stages becomes
better defined as the sulcus parolfactorius posterior. It is
here very short and does not extend so far up on the medial
surface as the furrow represented on the His-Ziegler model
of a brain approximately the same age and termed the fissura
prima. Furthermore it could not possibly cause a ventricular
swelling. A further shrinkage and lateral shift of the anterior
olfactory lobe would have just such a tendency to produce the
effect represented in the model and figures by His.
The evidence supports the view of Hochstetter that, in the
sense of the term used by His, namely, of a fissure which produces a swelling on the ventricular wall, there is no fissura
prima, but rather the beginning of the s. parolfactorius
posterior.
Figure 3 shows the globular form of a brain about 11weeks
old (62, table 1). On the medial surface there are some radial
furrows which are obviously postmortem effects.
Figure 4 (224842, table 2) gives the lateral view of a brain.
No age is given in the records, but from the recorded total
length of the fetus and the stage of development of the cerebellum, it is estimated at about 12 weeks. Figure 5 gives a
dorsal view of the same brain. A furrow is seen emerging at
the medial dorsal border of each hemisphere. This simulates
a parieto-occipital sulcus but is really due to a slight shrinkage which sharpens a natural concavity on the medial wall of
this region where it is thin. The concavity is present in all
well preserved specimens in this and later stages. Figure 6
gives a ventral view of the same brain showing the stage
reached in the development of the olfactory bulbs and tracts.
Figure 7 gives a lateral view of a brain of about the same
age (224722). Some increase in height in proportion to breadth
is apparent. The age given in the Museum records is “about
three months” and corresponds to the preceding, but may
possibly be a week older.
Fourth month. Figure 8 gives the lateral view of a brain
about the middle of the fourth month or 14 weeks. On the
121
DEVELOPMENT OF THE CEREBRAL SULCI
medial surface of this brain a shallow parieto-occipital depression is seen. No vestige of a posterior calcarine is visible,
though on the anterior medial surface some radial furrows
are present which are obviously postmortem effects.
TABLE 2
I
REOORDEDDATA
3rain
reight
gm.
1
AQE
Ird montl
10 weeks
12 ”
12.9 12 ”
12 ”
Lth mont€
190
9 9
>9
9 9
99
11
9 )
> Y
99
5th month
223
224847
224172
224848
272404
w $
w - Body Ig. 19.1
w 0 Body Ig. 19.7
w
9 9
17
>7
19
9 9
19
I
99
99
I
9 9
19
~
40.0 5th month’
> 9
-
47 .O
937
981
86.0
ILLUSTRA-
99
~
)’ I
7th month
”
’)
9 9
J 9
”
!
cm.
cm.
1.4
2.6
2.8
2.8
3.3
3.6
3.6
3.7
4.1
4.3
4.4
4.8
4.9
4.9
5.0
5.5
5.8
5.6
6.6
6.1
7.1
1.0
1.3
2.15 1.65
2.25 1.95
2.4
2.2
2.4
2.25
3.0
2.5
2.8
2.2
2.3
3.2
3.5
2.3
2.9
3.2
3.5
2.7
3.9
2.8
4.1
3.4
3.7
3.0
3.1
3.7
3.3
4.2
4.5
3.5
4.4
3.3
4.8
3.6
4.7
3.6
4.1
5.0
I
790
228088 w 2
249569 n d Body Ig. 46.4
86.0
91.0
1776
364
375
--
TIONS
Lgth. Brdth. Hght.
__
gm.
30.0
30.6
BUIN
11
9 9
,
99
9 9
,
I
3th month,
3th month
I
Neonatus,
Neonatus,
7.3
7.0
7.9
9.0
9.7
11.4
em.
Tigs. 4,5,6
Fig. 7
Fig. 9
Figs. 13 & 14
Figs. 1 7 & 18
Fig. 2 1
Figs. 24 & 25
Fig. 26
Figs. 27,28
& 29
5.3 4.3
4.6 Figs. 30 & 31
4.9
4.4 Fig. 32
5.6
7.1 5.3
7.3
5.6 Fig. 33
8.7 .. 6.8
.-
Figure 9 (228024) is that of a brain with an age according
to the records of “about four months.’’ It corresponds in
development with our next specimen, but there is a difference
in size due in part, I believe, to the different fixing fluids used
122
C. J. CONNOLLY
in the two series. This is true also of some other specimens.
The greatest height at this age period is at about the level
of the temporal pole. On the medial surface a well marked
furrow occurs in the middle of the parieto-occipital depression
and also in the calcarine region.
Figure 10 gives a dorsal view of a brain, resting on the
cranial basis, of a fetus ( 6 5 , table 1)age 16 weeks. The occipital lateral depression is seen on the dorsal medial border of
each hemisphere, forming a lozenge-shaped cavity between
the two hemispheres.
Figure 11gives the lateral view of a fetus of practically the
same C.R. length and same age, with a perfectly smooth lateral surface (G6, table 1). Figure 12 gives a medial view of
the same brain. Here we have, without doubt, an early stage
of the calcarine fissure. The occipital depression has also a
shallow furrow. These furrows cannot be due to the fixing
fluids, nor can they be postmortem changes, for the medial
surface of the brain of the preceding specimen (fig. 11) of
same size and age, presents an almost identical picture, so
that photographs can be dispensed with.
The parieto-occipital depression is true enough a shallow
furrow. The depression which Hochstetter describes and
which is present in our specimens must be the result of a lag
in the growth of this region compared to that of the neighboring cortex. It would seem to be a difference of degree of development and not of kind should a furrow be present. The
point in itself is perhaps not of great weight, but taken in
conjunction with growth processes referred to below, it is of
some morphological importance. Hochstetter shows that no
ventricular swelling is caused by this depression. The occipital depression with or without a defined sulcus increases in
prominence during the foIlowing months, but dwindles again
and finally disappears in later stages where, as in the adult
brain, its place is taken by a deep fissure.
Figure 13 gives a lateral view of brain 247374. The age
given in the records is “about four months.” Though smaller
than the last specimen discussed, it is at least as old. The
DEVELOPMENT O F THE CEREBRAL SULCI
123
ventral surface (fig. 14) shows a slightly further development.
The olfactory tracts and bulbs are now clearly differentiated
from the rest of the cortex and a well defined sulcus limits
them posteriorly and continues on the medial surface as the
s. parolfactorius posterior. The nucleus amygdalae ( g ~ r u s
semilunaris of Retzius) is separated from the adjacent cortex
by a shallow groove. The olfactory bulbs produce a slight
flattening of the brain surface but no olfactory sulcus is yet
developed. A parieto-occipital and a calcarine appear on both
hemispheres, but in specimen 247574 the calcarine is present
only on the right side.
F i f t h morzth. At the end of the fourth and the beginning
of the fifth month the hemispheres undergo a typical elongation in the occipital region as illustrated by all our specimens
of this period.
The next specimens illustrate conditions which have a bearing on the problem of what takes place on the medial surface
of the occipital region during this age period. Figure 15 gives
the lateral view of the brain of a fetus with a C.R. length of
13.4 em. (G8, table l), about 1 em. longer than the specimen
illustrated in figure 11and estimated to be 17 weeks olcl. The
brain is 2 mm. longer. The sylvian is seen to deepen by excess
growth of the neighboring cortex and its axis extends upward
and backward. There are no sulci on the lateral surface. I n
figure 16 a medial view of the same brain is shown. The calcarine is quite prominent, but not so the parieto-occipital. I n
the lower part of the occipital depression, however, a very
small but smooth furrow may be seen. Other specimens of
this age show similar furrows but more marked. Its presence
in varying degrees of prominence is dependent, I believe, on
the degree of development of the neighboring cortex.
The next specimen (224840) is slightly smaller than the
preceding, but from the development of the cerebellum and
the sylvian depression it is a t least as old and possibly a week
older. Figure 17 shows the lateral surface which is without
sulci. The photograph of the medial surface (fig. 18) shows
clearly the parieto-occipital and calcarine complex. The fixa-
124
C. J. CONNOLLY
tive has accentuated the gaping of the parieto-occipital furrow. Not only is the anterior calcarine or stem of the Y-shaped
formation present and confluent with the anterior part of the
posterior calcarine beyond the junction with the parietooccipital, but also the caudal part of the posterior calcarine
makes its appearance as a nearly vertical dent just caudal to
the anterior part. On the left hemisphere this caudal element
has superficially joined the anterior part. It is found in our
material more frequently on the right hemisphere than on
the left. The posterior calcarine thus follows the interrupted
mode of development as first described by Cunningham (1892).
Figure 19 gives the medial view of a brain (612, table 1)
estimated to be about 18 weeks old. It is considerably larger
than the preceding specimen but has still a smooth lateral
surf ace. The posterior calcarine has further lengthened, but
the parieto-occipital is a very shallow furrow.
The next specimen (G16) illustrated (fig. 20) is estimated
to be 20 o r 21 weeks old. It is considerably larger than the
preceding brain. The sylvian depression has become deeper.
The insula is yet wholly exposed, but its superior and inferior
limiting sulci are becoming sharply marked. The lateral surface has a faint depression in the position of the central sulcus.
This sulcus is better defined in the smaller brain 615. The
shallow mark near the caudal extremity was caused by the
pressure of the parietal bone at the lambdoid suture. Two
such furrows may easily form if the head of the fetus is even
slightly pressed against the container, The furrow just mentioned may simulate a lunate sulcus. The other may be produced at the corona1 suture and simulate a central sulcus
though it is more in the position of a precentral sulcus. These
artificial furrows have been interpreted as the above mentioned sulci in the older literature. On the medial surface both
calcarine and parieto-occipital fissures are present. On the
ventral surface an olfactory depression has an olfactory sulcus
in its caudal portion.
Figure 21 is that of a smaller specimen (224847) but more
advanced, as evidenced by the sylvian depression which is
DEVELOPMENT O F THE CEREBRAL SULCI
125
more clearly triangular. The specimen has probably suffered
some shrinkage. The lower part of the central sulcus is present. There are also dimples representing the precentral inferior and frontomarginal sulci. There is a Y-shaped parietooccipital and calcarine formation on the right hemisphere,
and on the left, in addition, the caudal element of the posterior
calcarine.
Similar furrows, in some respects more marked are also
present in specimen 224849. The olfactory sulcus is present
in the caudal two-thirds of the depression and extends beyond
the anterior limit of the olfactory bulbs. It thus appears not
to be caused by the olfactory tracts but to form independently
though no doubt receiving its stimulus from them. I n this
specimen the caudal element of the posterior calcarine is present in both hemispheres but in the left, the anterior part of
the posterior calcarine is but a small spur.
According to the evidence of our material the faint beginnings of sulci on the lateral surface may be discerned at the
end of the fifth month. Among our specimens are some much
older which are without sulci on the lateral surface. The
sylvian fissure may even be closed for the greater part yet
few sulci and of very irregular pattern appear. These are
not cases of normal variation; they are “sick” brains-pathological specimens.
Sizth month. Figure 22 shows the left hemisphere of a brain
estimated to be 21 weeks old. The brain is long compared to
breadth and height and there is considerable advance in the
closing of the insula. There is a shallow depression in the
position of the lower part of the central sulcus and in the
frontal, temporal and parietal regions faint dimples occur.
The furrow at the caudal end is a postmortem effect. The
medial surface (fig. 23) presents a clear-cut parieto-occipital
and calcarine complex. The expansion of the cortex has sharpened and deepened the two fissures so that we have a further
development of essentially the same condition represented in
an earlier stage (fig. 12).
126
C. J. CONNOLLY
The sulci on the lateral surface definitely take form during
this month. There is a great expansion of the cortex apparently distributed over the whole surface of the hemispheres.
This expansion is exemplified in the closing of the insula at
its caudal extremity. The lower part of the central sulcus
may appear before the rest of the furrow though not necessarily in that sequence. At any rate the entire central sulcus
soon crosses the surface almost to the medial border and is
accompanied by the appearance of the other principal sulci.
This is brought out by the very interesting stage represented in figure 24 (224848). The central sulcus (c) of the
right hemisphere is a continuous, slightly curved furrow extending almost to the dorsal border. The other principal sulci
are represented by shallow depressions. The precentral inferior (pci) is somewhat faintly shown in the photograph when
compared with the specimen, but otherwise the illustration
represents very well the actual conditions. Above the precentral inferior is the oblique precentral superior (pcs) and
anterior to it, a small furrow, the frontal superior (fs). A
small dent in front of the precentral inferior is doubtless the
frontal inferior (fi). Near the frontal pole is a curved sulcus,
the frontomarginal (fmg). It is significant that the frontomarginal, though not always present in brains of this age
period, may appear early in ontogenetic development. The
postcentral inferior (pti) and its closely related intraparietal
has made a beginning, and also the superior temporal (ts).
The furrow near the caudal extremity is factitious.
The left hemisphere (fig. 25) shows a similar condition. The
central sulcus is not so clearly brought out in the photograph
as the precentral. The frontomarginal is better developed
than on the right hemisphere and is triradiate in form. On
the medial surface elements of the callosomarginal sulcus
appear. On the left hemisphere no posterior calcarine is seen,
and a mere vestige of a parieto-occipital. On the right hemisphere there is a very short posterior calcarine in the position
of its caudal section. The parieto-occipital in compensation
DEVELOPMENT OF THE CEREBRAL SULCI
127
is a well developed fissure continuing the course of the anterior calcarine.
Seventh rnomth. The next specimen (228445) is estimated
to be a t the beginning of the seventh month. The intraparietal
(fig. 26) is further advanced, but the most prominent additional feature is the development of the superior temporal or
parallel sulcus, showing as does its primate history, that it is
one of the principal sulci. On the medial aspect of this brain
a Y-shaped parieto-occipital and calcarine complex is present
and there are small furrows, as in the previous specimen,
which are interpreted as the beginnings of the callosomarginal
sulcus.
Figures 27, 28 and 29 represent the brain of a fetus with a
length of 23 em. and estimated to be 25 or 26 weeks old. All
the principal sulci appear in diagrammatic clearness. The
insula is being submerged caudally and on its exposed surface
the faint furrows of its own beginning fissuration can be recognized. A single anterior horizontal branch ( h ) of the sylvian
has formed. A second small furrow is seen just above but
unconnected with the superior limiting sulcus of the insula.
It has been suggested by some that such a sulcus may form
the ascending anterior branch by secondarily uniting with the
superior limiting sulcus. But even if that be true at times,. the
usual method of forming the two anterior branches of the
sylvian is that described by Cunningham, wherein a wedgeshaped mass of cortex grows downward and backward to form
the frontal operculum, being separated from the frontoparietal operculum by the ascending branch and from the
orbital by the horizontal branch.
On the right heiiiisphere a single branch has formed. I n
another specimen of about this age the frontal operculum is
just beginning to form on the left hemisphere, and the very
beginnings of the two branches can be recognized while the
right hemisphere has a single branch. Early in the seventh
lunar month it is apparently decisive whether a frontal operculum or pars triangularis is to form or not. In all but one of
128
C. J. CONNOLLY
the specimens of this age period, the frontal operculnm is
forming on the left hemisphere but not on the right.
Issuing from the precentral inferior (pci) is the frontal
inferior (fi). The precentral superior (pcs) is now recognizable as a sulcus distinct from the frontal superior (fs) which
issues from it as a long sagittal furrow. Anterior to it and
near the frontal pole is the frontomarginal (fmg). Between
the frontal superior and inferior sulci and better developed
on the right side, is a sagittal furrow which is interpreted as
the midfrontal sulcus. I n form and position it is similar to
the horizontal branch of the fundamental arcuate sulcus of
primates. Anterior to the precentral inferior is the diagonal
(d). Very striking in this specimen is the well developed postcentral (pti) sulcus which on both sides runs parallel to the
central sulcus for almost the whole of its length (fig. 29).
The intraparietal (ip) sulcus is seen in two separate triradiate sections with a third element between them. The most
caudal of these is the paroccipital with its bifurcation, the
transverse occipita1. This ends caudal to the parieto-occipital
fissure (PO) which now crosses the medial border to appear
on the lateral surface of the brain. A lunate sulcus (1) is present on both hemispheres. The furrow is quite unlike the postmortem furrows already discussed. On the right hemisphere
it is more prominent and more typically lunate in form with
a marked anterior convexity. The temporal superior (ts) ends
with a bifurcation on the left. Superficially united with it is
the sulcus angularis. A clearly defined midtemporal sulcus
(tm) appears below the caudal part of the superior temporal.
On the ventral surface the olfactory sulcus has further developed and is provided with a small medial and lateral branch
a t its caudal extremity. On the lateral portion of the orbital
surface of both hemispheres a small oblique furrow, the orbital sulcus, is present. A posterior rhinal fissure is now clearly
defined and also a sagittal, slightly curved collateral sulcus
together with the transverse collateral. On the medial surface, the parieto-occipital and calcarine form the typical Yshaped complex. The posterior calcarine is forked caudally
DEVELOPMENT OF THE CEREBRAL SULCI
129
on the right, while it ends without branches on the left side.
A callosomarginal is present in two separate parts.
Another specimen of this age group with the same brain
weight (86 gm.)has slightly less developed sulci, though all
the principal sulci are laid down. The postcentral inferior
does not form a continuous furrow with the superior, but is
rather continuous with an element of the intraparietal.
A somewhat larger and heavier brain is 221123, a drawing
of which is given in figure 30. The insula is more operculated
and a definite frontal operculum (F) is forming, being limited
by the anterior horizontal ( h ) and ascending (a) rami. The
fissuration has reached about the same degree of development
as .the preceding specimen, but the furrows are more interrupted. The central sulcus (c) is a slightly bent furrow. The
precentral inferior (pci) is strongly developed and a separate
frontal inferior (fi) is seen above the ascending ramus of the
sylvian fissure. The postcentral is more typically divided into
a superior (pts) and an inferior (pti) part. The other sulci
need no comment.
The medial surface of this specimen is shown in the photograph (fig. 31). The Y-shaped parieto-occipital and calcarine
condition is clear cut, and there is a shallow depression at the
dorsal end of the parieto-occipital fissure indicating the formation of a paracalcarine sulcus. The callosomarginal is also
quite definitely represented in two sections and a sulcus has
formed in the precuneus lobe. On the ventral surface the
same sulci are present as in the previous specimen, but are
not so well developed.
Eighth month. There is but one specimen in the collection
about which one can be reasonably sure that it belongs to the
eighth month. The weight of the fetus was 1776 gm., which
places it well within the range of variation for this period.
The brain is soft and the right hemisphere is damaged. The
sulci on the right hemisphere, however, are intact and I have
made a drawing based on careful measurements (fig. 32). The
size of the brain and the degree of fissuration agree with the
130
C.
J. CONNOLLY
expected advance over the seventh month, and it is decidedly
less advanced than specimens of the ninth month.
The advance in fissuration is seen in the bending and branching of the principal sulci already present in the seventh month,
and also in the development of secondary sulci (e.g. midtemporal and subcentral anterior). The angular sulcus (ang)
has split off from the parallel sulcus (ts), and an anterior
occipital (aoc) has formed. The insula is further operculated
and a single anterior branch ( a ) of the sylvian has formed.
The diagonal ( d ) has linked up with an element of the inferior
frontal (fi) which has become branched. The midfrontal (fm)
has reached a remarkable development and ends anteriorly
near the frontomarginal sulcus (fmg). An interesting stage
is seen in the intraparietal sulcus (ip) which still revealing
its three distinct parts, has become wavy and connected with
the postcentral sulcus. Its caudal fork is the transverse occipital (otc). Above the intraparietal is the superior parietal
(ps). On the medial surface the callosomarginal has further
developed. The anterior element has branched and its caudal
end overlaps for a considerable distance the anterior end of
the mid portion. The caudal end of the posterior calcarine is
forked, its branches coming on the lateral surface (re).
Ninth month. Several good specimens of this period ase
present in the Museum series and measurements of typical
ones are given in table 2. Among the specimens of this period
occur some with interesting variations which will need more
discussion than space permits in this paper. They can, moreover, be more advantageously treated in relation to conditions
in the adult brain, which the writer hopes to do on another
occasion.
Figure 33 is a photograph of a specimen (228357) of a White
newborn. The brain is in perfect condition and obviously well
developed. The sulci are not only much branched but very
tortuous in their course.
V3ry striking is the degree to which the insula is covered.
It is often stated that the insula is covered only during the
DEVELOPMENT O F T H E CEREBRAL SULCI
131
first year of infancy. If that be normally true we have here
at least a very interesting variation, for the insula is covered
to a greater degree than even in the aged adult. And there
can be no question as t o the age of this specimen for according
to the Museum record, death occurred at birth.
DISCUSSION AND SUMMARY
The conditions of appearance of the parieto-occipital and
calcarine fissures present special difficulties in a summary
statement. These fissures, as Hochstetter has shown, do not
appear in the second and third months. The evidence of this
study regarding the third month, supports this view, though no
histological examination was made. But these fissures may
be present a t the end of the fourth month (fig. 12) though it
is true that one o r other (most frequently the parieto-occipital) may be absent up to the seventh month (figs. 16 and 19).
They certainly may appear early in the fifth month before
any sulci on the lateral surface (figs. 17 and 18). Even at the
end of the third month special conditions prevail in the
parieto-occipital region (fig. 5) ; the wall is thin here and an
occipital depression normally occurs.
Wen ('33) made a histological study of the occipital region
in the Chinese fetal brain between the fourth and seventh
months. He accepts the view that the calcarine and parietooccipital fissures appear simultaneously as precursors toward
the end of the second or beginning of the third month. These
may be retained to the fourth month, but by the fifth they are
completely obliterated and are succeeded by permanent fissures in the sixth. Wen gives a figure of such a precursor in
a fetal brain as old as 17 weeks. No mention, however, is made
of the work of Hochstetter who limited his investigation to the
earlier months and did not further follow the sequence of
the appearance of the sulci, and no histological examination
was made by Wen of brains previous to the end of the fourth
month.
I have interpreted the fissures in a brain of similar age as
permanent fissures. The six-layered condition characteristic
132
C. J. CONNOLLY
of the visual cortex appears according to Brodmann ('25) as
early as the fifth month. The earliest appearance of the calcarine in our material is that of a 16-week fetus or end of
fourth month (fig. 12), while there is no question of a true
Y-shaped parieto-occipital and calcarine complex at the beginning of the fifth month (fig. 18) which agrees fairly well
with Brodmann's data.
The presence or absence of a parieto-occipital furrow from
the end of the fourth to the end of the sixth month appears
to depend upon the relative degree of development of the
neighboring cortex. The writer ('36) has shown that the
presence or absence of the lateral or external calcarine in
Cercopithecidae depends upon the degree of development of
the cortex in front of the lunate. I n Presbytis the lower
branch becomes established, but the dorsal branch may be
a shallow depression or a well defined sulcus depending upon
the development of the cortex anterior to it, though no
change in histological differentiation occurs. The faint depression or deep sulcus is in either event an axial furrow of
the visual cortex. Likewise the occipital depression in the
human fetal brain may or may not have a furrow depending
on the development of the adjacent cortex. With or without
a furrow the occipital depression increases in prominence
during the fifth and sixth months, but in the growth process
it must finally yield to relieve the tension, and a deep furrow
is formed before the seventh month, which appears on the
dorsal surface of the brain (fig. 29).
The calcarine is more rarely lacking and when this occurs
the parieto-occipital is strongly developed in compensation.
When either is absent after the seventh month we have probably to do with an abnormal condition. The process is here
interpreted as an illustration of what Cunningham called
growth antagonisms.
The sulci on the lateral surface may be seen as faint dimples
or shallow furrows at the end of the fifth or beginning of the
sixth month. During the sixth they develop further, and at
DEVELOPMERT O F THE CEREBRAL SULCI
133
the middle of the seventh, all the principal sulci are laid down
usually in a simple form. In the eighth month the sulci become
branched and tortuous and secondary sulci become marked.
In the last month of fetal life the brain becomes rich in furrows with many secondary and tertiary sulci as if a miniature
adult and at birth the insula may be almost completely
covered.
LITERATURE CITED
AREY,L. B. 1936 Developmental Anatomy. 3rd ed. Philadelphia.
ARIENSKAPPERS,C. U. 1913 Cerebral localization and the significance of sulci.
Eighteenth Intern. Congr. Med. London.
BRODMANN,
K. 1925 Vergleichende Localisationslehre der Grosshirnrinde. Leipzig.
C. J. 1936 The fissural pattern of the primate brain. Am. J. Phys.
CONITOLLY,
Anthrop., XXI, 301-422.
CUNNINGIIAM,
D. J. 1892 Contribution to the surface anatomy of the cerebral
hemispheres. Roy. Irish Acad. Sci. Cunningham Memoirs, no. VII.
Dublin.
HINES,
M. 1922 Studies i n the growth and differentiation of the telencephalon
in man. The fissura hippocampi. J. Comp. Neur., XXXIV, 73-171.
HIS, 1
%
'
. 1889 Die Formentwicklung des menschenlichen Vorderhirns vom ersten
bis zum Beginn des dritten Monats. Abh. math-phys. El. d. Kgl. Sachs.
Ges. Wiss. XV.
1904 Die Entwieklung des menschlichen Gehirns. Leipzig.
H O C H S W ~F.
, 1898 Beitrage zur Entwicklungsgeschichte des Gehirns. Bibliotheca niedica. Abt. A. Anatomie. Stuttgart.
1924 Ueber die Entwicklung des Gehirns. Anat. Anz., LVIII.
HRDLICKA, A. 1906 Brains and brain preservatives. Proc. 1.. S. Nat. Mus.,
XXX, 245-320.
J. 1907 Handatlas der Entwicklungsgeschichte des Menschen. Jena.
KOLLNANN,
MALL,F. P. 1910 Determination of the age of human embryos and fetuses. I n
Human Embryology by Keibd and Mall. I.
RETZIUS,
G. 1896 Das Menschenhirn. Jena.
1901 Zur Frage von den sogenannten transitorischen Furchen des
Menschengehirns. Anat. Am., XIX.
SMITH,G. ELLIOT 1931 I n Cunningham's Text-book of Anatomy, p. 629. 6th ecl.
STREETER,
G. L. 1920 Weight, sitting height, head size, foot length and menstrual age of the human embryo. Contr. to Embr., XI, Carnegie Inst.
Wash. no. 55.
TYEW, I. C. 1933 A study of the occipital region of the Chinese fetal brain.
J. Coinp. Neur., LVII, 477-506.
PLATE 1
EXPLANATION OF FIGURES
Lateral view of a brain about 10 weeks old.
Medial view of the same brain.
Lateral view of a brain about 11 weeks old.
Lateral view of a brain about 1 2 weeks old.
Dorsal view of the same brain.
Ventral view of the same brain.
Lateral view of a brain about same age as preceding.
Lateral view of a brain about 14 weeks old.
Lateral view of a brain about 4 months old.
134
DEVELOPJIENT OF THE CEREBRAL SULCI
C. J. CONNOLLY
PLATE 1
PLATE 2
EXPLANATION OF FIGURES
10
11
12
13
14
15
Dorsal view of a brain 16 weeks old.
Lateral view of a brain of same age as that of figure 10.
Medial view of the same brain.
Lateral view of a brain about 4 months old.
Ventral view of the same brain.
Lateral view of a brain about 17 weeks old.
1:to
DEVELOPMENT OF THE CEREBRAL SULCI
C. J. COMNOLLY
137
PLATE 2
PLATE 3
EXPLANATION OF FIGURES
16 Xedial view of the same brain as figure 15.
17 Lateral view of a brain at beginning of fifth month.
18 Medial view of the same brain.
19 Medial view of a brain about 18 weeks old.
"0 Lateral view of a brain about 20 or 21 weeks old.
138
DEVELOPMENT OF THE CEREBRAL SULCI
C. J . COXNOLLY
139
PLATE 3
PLATE 4
EXPLANATION OF FIGURES
21 Lateral view of a brain at latter part of fifth month.
22 Lateral view of a brain about 21 weeks old.
23 Medial view of the same brain.
140
DEVELOPMENT OF THE CEREBRAL SULCI
C. J. CONNOLLY
141
PLATE 4
PLATE 5
EXPLANATION OF FIGURES
24 Right hemisphere of a braiii a t early part of sixth month. c, central sulcus;
pci, precentral inferior; pcs, preceutral superior ; fs, frontal superior; fi, frontal
inferior; fmg, frontomarginal ; ts, temporal superior ; pti, postcentral inferior.
25 Left hemisphere of the same brain.
26 Right hemisphere of a brain a t beginning of the seventh month.
142
DEVELOPMENT OF THE CEREBRAL SULCI
C. J . CONNOLLY
143
PLATE 5
PLATE 6
EIIPLANATION OF FIQURES
27 Lateral view of a brain about 26 weeks old.
28 Drawing of the same brain. c, central snlcus; pci, precentral inferior; fi,
frontal inferior; d, diagonal; h, anterior horizontal branch of sylvian; pcs, precentral superior; fs, frontal superior; fm, midfrontal; fmg, frontomarginal; pti,
postcentral inferior ; ts, temporal superior; tm, midtemporal; ip, intraparietal ;
PO, parieto-occipital; 1, lunate.
29 Dorsal view of the same brain.
144
DEVELOPMENT 0%THE CEREBRAL SULCI
0 . J. CONNOLLY
145
PLATE 6
PLATE 7
EXPLANATION OF FIGURES
30 Drawing of the left hemisphere of a brain in seventh month. c, central
sulcus; pci, precentral inferior; fi, frontal inferior; F, frontal operculum; h,
anterior horizontal; a, anterior ascending branch of sylvian (S) ; pcs, precentral
superior; fs, frontal superior ; fmg, frontomarginal; pti, postcentral inferior;
pts, postcentral superior; ts, temporal superior ; tm, midtemporal; ip, intraparietal;
PO, parieto-occipital.
31 Medial view of the same brain.
146
DEVELOPYENT OF THE CEREBRAL SULCI
C. J. CONNOLLY
147
PLATE
8
EXPLANATION OF FIGURES
32 Drawing of the right hemisphere of a brain in the eighth month. c, central
sulcus; pci, precentral inferior; fi, frontal inferior; d, diagonal; a, single anterior
branch of sylvian ; pcs, precentral superior ; fs, frontal superior ; fm, midfrontal ;
fmg, frontomarginal; pti, postcentral inferior; pts, postcentral superior; ts, temporal superior ; tm, midtemporal; ang, angularis; ip, intraparietal ; ps, superior
parietal; par, paroccipital; otc, transverse occipital ; aoc, anterior occipital ; PO,
parieto-occipital ; re, retrocalcarine (posterior cal.)
33 Brain of the newborn.
.
148
DEVELOPMENT OF THE CEREBRAL SULCI
C.
J. CONNOLLY
149
PLATE 8
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