A
COMPARATIVE
SThDY
OF
THE
ANTERIOR
CEREBRAL
ARTERY
AND
THE
CIRCLE
OF
WILLIS
IN
PRIMATES
By
JAMES
W.
WATTS,
M.D.
Laboratory
of
Physiology,
Yale
University
School
of
Medicine,
New
Haven,
Conn.,
U.S.A.
I.
INTRODUCTION
IN
attempting
to
approach
the
hypothalamus
of
monkeys
by
transaction
of
the
corpus
callosum,
the
anterior
cerebral
artery
proved
to
be
a
source
of
unexpected
difficulty
(Watts
and
Fulton,
1934).
While
retracting
the
vessel
laterally
to
pass
an
instrument
between
it
and
the
falx
cerebri,
branches
were
seen
passing
from
the
single
arterial
trunk
to
both
hemispheres.
Examination
of.
the
brains
of
other
specimens
of
this
species
of
monkey
(Macaca
mulatta)
showed
that
each
anterior
cerebral
artery
runs
antero-medially
toward
the
longitudinal
fissure
of
the
cerebrum,
where
it
joins
its
fellow
to
form
a
single
trunk
which
passes
forward
into
the
fissure.
Within
the
fissure
the
anterior
cerebral
artery
lies
close
to
the
rostrum
and
body
of
the
corpus
callosum,
and
sends
cortical
branches
to
the
medial
surfaces
of
both
hemispheres.
This
led
to
a
systematic
examination
of
the
anterior
cerebral
artery
and
circle
of
Willis
in
all
available
Primate
brains,
and
the
results
of
the
study
are
recorded
in
the
present
paper.
The
earliest
description
of
the
cerebral
blood
vessels
of
a
subhuman
Primate
which
could
be
found
in
the
literature
is
by
Tyson
(1699).
This
author
made
a
careful
study
of
the
anatomy
of
a
chimpanzee
which
he
erroneously
designated
as
an
"orang-utan"
or
alternatively
as
a
"pigmie."
Of
the
struc-
tures
on
the
base
of
the
brain
he
wrote1:
"...On
the
basis
of
the
Brain,
we
may
view
all
the
Ten
pair
of
Nerves
exactly
situated
and
placed
as in
a
Humane
Brain;
nor
did
I
find
their
Origina-
tions
different,
or
any
Particularity
that
was
so.
I
shall
therefore
refer
to
the
figures
I
have
caused
to
be
made
of
the
Brain,
and
their
Descriptions;
where
we
may
observe the
Arteriae
Carotides,
Vertebrales,
and
Communicans,
and
the
whole
of
the
Blood
Vessels
in
our
Pygmie
to
be
the
same
as
in
a
Man."
The
first
observations
on
the
distribution
of
the
anterior
cerebral
artery
of
the
subhuman
Primates
which
could
be
found
were
by
Theile
(1852).
This
author,
in
a
study
of
the
entire
arterial
system
of
four
specimens
of
Simia
inuus,
refers
to
the
anterior,
middle,
and
posterior
cerebral
arteries
and
the
1
Tyson
(1699),
see
p.
56.
Anterior
Cerebral
Artery
and
Circle
of
Willis
in
Primates
535
posterior
communicating
artery.
Of
the
anterior
cerebral
artery
which
he
calls
the
arteria
corporis
callosi
he
wrote:
"Sie
wendet
sich
nach
vorwdrts
und
einwarts
in
die
Spalte
zwischen
den
beiden
vordern
Hirnlappen,
und
hier
fliessen
die
rechte
und
linke
Arterie
zu
einem
unpaaren
Aste
zusammen,
ohne
aber
an
Dicke
zuzunehmen.
Diese
gemeingeschaftliche
Art.
corporis
callosi
verlauft
zwischen
den
beiden
vordern
Hirnlappen
nach
vorwdrts,
biegt
sich
uber
das
Balkenknie
nach
oben
und
hinten
und
versorgt
beide
vordern
Hirnlappen,
so
wie
den
Balken."
An
unusual
opportunity
for
making
a
comparative
study
of
the
cerebral
arteries
presented
itself,
because
of
the
large
number
of
Primates
used
for
experimental
purposes
in
this
laboratory.
Some
of
the
specimens
were
examined
in
the
fresh
state
but
the
majority
after
fixation
in
formalin
or
alcohol.
The
arachnoid
was
dissected
away
and
the
blood
vessels
studied
in
situ.
II.
MATERIAL1
Family
PONGIDAE,
the
anthropoid
apes
Genus
Pongo
Pongo
pygmaeus,
orang-utan
...
...
...
Genus
Pan
Pan
8atyrU8,
chimpanzee
...
... ...
Family
HYLOBATIDAE,
the
lesser
apes
Genus
Hylobates
Hylobates
lar
(H.
leuciscus),
lar
gibbon
...
Hylobates
hoolock,
hoolock
gibbon
...
Family
CERCOPITHECIDAE,
the
Old
World
monkeys
Genus
Cercopithecus
Cercopithecus
sabeus,
green
monkey
...
...
Genus
Erythrocebus
Erythrocebus
patas,
patas
or
hussar
monkey
...
Genus
Cercocebus,
the
mangabeys
Cercocebus
aethiops,
sooty
mangabey
...
...
Cercocebus
torquatus,
white-crowned
mangabey
Genus
Macaca,
the
macaques
Macaca
mulatta,
the
rhesus
monkey.
Genus
Papio,
the
baboons
Papio
cynocephalus,
yellow
baboon
...
Papio
hamadryas,
hamadryas
baboon.
...
Family
CEBIDAE,
the
New
World
monkeys
Genus
Cebus
Cebus
azarae,
Azara's
capuchin
...
...
Genus
Lagothrix,
woolly
monkeys
...
Genus
Ateles,
spider
monkeys
Ateles
ater,
black-face
spider
...
...
...
No.
of
brains
examined
4
6
1
1
19
7
5
3
58
10
1
2
3
5
Total
125
1
The
classification
used
by
Zuckerman
(1932)
has
been
adopted
(see
Fulton
and
Zuckerman,
1934,
in
preparation).
James
W.
Watts
III.
PONGO
PYGMAEUS,
ORANG-UTAN
The
arterial
circle
of
Willis
of
the
orang-utan
is
a
polygon
formed
at
the
base
of
the
brain
by
branches
from
the
internal
carotid
and
basilar
arteries
(fig.
1).
The
internal
carotid
artery
reaches
the
brain
between
the
temporal
lobe
and
the
optic
chiasm,
runs
antero-laterally
a
distance
of
4
or
5
mm.
and
divides
near
the
anterior
perforated
substance
into
its
terminal
branches,
the
anterior
and
middle
cerebral
arteries.
It
thus
forms
a
part
of
the
lateral
boundary
of
the
circle.
The
posterior
communicating
artery,
much
smaller
in
calibre
than
either
of
the
other
branches,
forms
a
connection
between
the
internal
carotid
and
posterior
cerebral
arteries.
The
middle
cerebral
artery,
usually
the
larger
of
the
two
terminal
branches
of
the
internal
carotid,
runs
laterally
into
the
Sylvian
fissure,
taking
no
part
in
the
formation
of
the
arterial
circle.
The
anterior
cerebral
artery
curves
antero-medially,
and
is
joined
to
its
fellow
of
the
opposite
side
by
the
anterior
communicating
artery
to
form
an
arch.
From
this
arterial
arch,
separated
from
each
other
by
2-3
mm.,
two
anterior
cerebral
arteries
of
approximately
equal
calibre
run
forward
into
the
longitudinal
fissure
of
the
cerebrum.
Within
the
fissure,
each
anterior
cerebral
artery
lies
on
the
medial
surface
of
its
respective
hemisphere
close
to
the
rostrum
and
body
of
the
corpus
callosum.
The
artery
sends
cortical
branches
to
the
medial
and
superior
aspects
of
the
frontal
and
parietal
lobes.
One
merit
of
the
nomenclature
of
the
cortical
branches
of
anterior
cerebral
artery
given
by
Hindze
(1927,
1930)
for
the
gorilla
and
the
chimpanzee
is
that
the
name
of
the
vessel
indicates
its
area
of
distribution.
These
branches
were
easily
identified
in
most
of
the
orang-utan
brains
which
formed
the
basis
of
the
present
study.
The
following
outline
according
to
Hindze
gives
the
distri-
bution
of
the
branches
of
the
anterior
cerebral
artery:
1.
Anterior
perforating-to
the
anterior
perforated
substance.
2.
Posterior
orbital-to
the
rectus
and
the
posterior
part
of
the
orbital
gyri.
3.
Anterior
orbital-to
the
anterior
part
of
the
gyrus
rectus
and
the
orbital
gyri,
to
the
frontal
pole,
and
the
medial
surface
under
the
subrostral
sulcus.
4.
Anterior
frontal-to
the
medial
surface
above
the
subrostral
sulcus
and
the
frontal
pole.
5.
Middle
frontal-to
the
medial
surface
above
the
distribution
of
the
anterior
frontal
artery
and
to
the
middle
third
of
both
frontal
gyri.
6.
Posterior
frontal-to
the
medial
and
dorsal
surfaces
of
the
posterior
third
of
the
upper
frontal
gyrus.
7.
Callosal-to
the
corpus
callosum
and
its
sulcus
(as
a
distinct
branch
this
was
often
absent
on
one
or
both
sides
in
this
series).
8.
Superior
precentral-to
the
paracentral
lobule
and
the
superior
part
of
536
Anterior
Cerebral
Artery
and
Circle
of
Willis
in
Primates
537
the
precentral
and
postcentral
gyri.
(Hindze
does
not
mention
its
distribution
to
the
precentral
gyrus,
but
a
relatively
large
twig
is
regularly
present.)
9.
Superior
posteentral-to
the
same
areas,
a
little
posteriorly.
10.
Precuneal-to
the
precuneus
and
the
superior
part
of
the
postcentral
gyrus.
The
internal
distribution
of
the
arteries
entering
the
anterior
perforated
space
has
been
completely
worked
out
by
Beevor
(1909)
for
the
human, and
since
Shellshear
(1927)
has
found
their
distribution
in
the
orang-utan
so
similar
to
that
of
Man,
the
internal
arteries
have
not
been
investigated
in
this
study.
Fig.
1.
Fig.
2.
Fig.
1.
Orang-utan.
The
two
anterior
cerebral
arteries
run
parallel
to
each
other
and
are
joined
together
by
a
thick
anterior
communicating
artery.
Fig.
2.
Orang-utan.
Like
fig.
1.
In
addition,
a
loop
is
present
in
the
left
anterior
cerebral
artery,
and
a
small
branch
joins
the
two
posterior
communicating
arteries
together.
The
anterior
communicating
artery
connects
the
two
anterior
cerebrals
at
the
entrance
to
the
longitudinal
fissure.
The
communicating
artery
in
the
orang-utan
is
about
3
or
4
mm.
long,
and
it
has
as
great
a
diameter
as
the
arteries
which
it
connects.
'The
posterior
cerebral
arteries,
formed
by
the
bifurcation
of
the
basilar
at
the
upper
border
of
the
pons,
make
up
the
posterior
boundary
of
the
circle
of
Willis.
The
posterior
cerebral
passes
anterior
to
the
oculomotor
nerve
where
the
nerve
leaves
the
brain,
and
then
curves
posteriorly
around
the
cerebral
peduncle.
In
one
specimen,
the
left
anterior
cerebral
artery
divides
to
form
a
loop
close
to
the
mouth
of
the
longitudinal
fissure
(fig.
2).
In
the
same
brain,
three
distinct
branches
arise
from
the
right
internal
carotid
artery
and
are
distri-
buted
to
the
territory
of
the
middle
cerebral
artery;
from
the
opposite
carotid
538
James
W.
Watts
arise
two
branches
supplying
this
region
of
the
left
hemisphere.
There
is
also
a
connecting
branch
between
the
posterior
communicating
arteries.
The
fourth
brain
differs
from
those
already
described
since
it
has
three
anterior
cerebral
arteries,
the
left
with
the
usual
branches
and
distribution
(fig.
3).
The
right
runs
forward
in
the
longitudinal
fissure
distributing
branches
to
the
gyrus
rectus
and
the
medial
surface
of
the
hemisphere
below
the
corpus
callosum.
The
anterior
frontal
artery,
which
is
the
terminal
branch,
runs
near
the
cingulate
sulcus
to
the
superior
frontal
gyrus.
The
middle
anterior cerebral
artery
runs
forward
into
the
fissure
and
lies
close
to
the
rostrum
and
body
of
the
corpus
callosum
without
branching
until
it
reaches
the
middle
third
of
K~
Fig.
3.
Fig.
4.
Fig.
3.
Orang-utan.
Three
anterior
cerebral
arteries
are
present
in
this
specimen.
Fig.
4.
Chimpanzee.
The
large
trunk
formed
by
the
union
of
the
right
and
left
anterior
cerebral
arteries
bifurcates
before
reaching
the
genu
of
the
corpus
callosum.
A
rudimentary
anterior
cerebral
arises
just
to
the
left
of
the
main
trunk.
the
corpus
callosum.
Then
the
artery
sends
branches
to
the
paracentral
lobule
and
to
the
precuneous.
Three
of
the
four
orang-utans
used
in
the
present
investigation
have
two
anterior
cerebral
arteries
which
run
parallel
to
each
other
within
the
longi-
tudinal
fissure,
each
lying
on
the
medial
surface
of
its
respective
hemisphere
close
to
the
corpus
callosum.
The
arteries
are
jointed
together
at
the
entrance
of
the
fissure
by
an
anterior
communicating
artery
of
large
size.
The
fourth
brain
has
three
anterior
cerebral
arteries
which
run
within
the
fissure.
The
reports
of
other
authors
relating
to
the
cerebral
blood
vessels
of
the
orang-utan
are
in
general
agreement
with
my
findings.
Tyson
(1699)
con-
$idered
the
arteries
of
the
base
of
the
brain
in
his
specimen
similar
in
every
respect
to
those
of
Man.
Bolk
(1901)
found
the
anterior
communicating
artery
Anterior
Cerebral
Artery
and
Circle
of
Willis
in
Primates
539
absent
so
that
the
circle
of
Willis
was
not
closed
in
the
two
orang-utan
brains
which
he
examined.
Grunbaum
and
Sherrington
(1902),
like
Tyson,
noted
that
the
circle
of
Willis
in
their
specimen
had
an
arrangement
like
that
of
a
Man.
Rothmann
(1904)
studied
the
brains
of
four
orang-utans,
in
three
of
which
there
were
two
anterior
cerebral
arteries
connected
by
a
communicating
branch,
and
in
one
there
were
three
anterior
cerebrals.
In
a
recent
study
of
the
blood
vessels
of
the
brain,
Shellshear
(1927)
observed
two
anterior
cerebral
arteries
connected
by
a
communicating
branch;
the
left
anterior
cerebral
divided
to
form
a
perforation
just
ventral
to
the
medial
olfactory
stria.
IV.
PAN
SATYR
US,
CHIMPANZEE
On
superficial
examination
the
circle
of
Willis
and
the
anterior
cerebral
arteries
of
the
chimpanzee
appear
very
similar
to
those
of
the
orang-utan.
The
posterior
cerebral
arteries
are
formed
by
the
bifurcation
of
the
basilar,
and
these
are
connected
with
the
internal carotids
by
the
smaller
posterior
communicating
arteries.
Likewise,
the
internal
carotid
artery
divides
into
its
two
terminal
branches,
the
middle
and
anterior
cerebral.
The
middle
cerebral
artery
runs
laterally
into
the
fissure
of
Sylvius
without
forming
a
part
of
the
boundary
of
the
polygon.
A
comparison
of
the
relative
size
of
the
anterior
and
middle
cerebral
arteries
of
the
six
orang-utan
brains,
showed
the
middle
was
larger
than
the
anterior
in
five
of
them.
In
the
sixth
brain,
the
anterior
cerebral
was
larger
than
the
middle
on
one
side.
The
anterior
cerebral
artery
runs
medially
in
a
nearly
transverse
direction
to
unite
with
the
same
artery
of
the
other
side
to
form
a
single
trunk
which
then
passes
into
the
longitudinal
cerebral
fissure
(fig.
4).
Within
the
fissure
the
artery
continues
as
a
single
trunk
nearly
as
far
as
the
rostrum
of
the
corpus
callosum
where
it
divides
into
two
anterior
cerebral
arteries,
one
running
along
the
medial
aspect
of
each
hemisphere
supplying
cortical
branches
on
the
way.
Four
of
the
specimens
have
a
rudimentary
left
anterior
cerebral
artery
which
enters
the
longitudinal
fissure
(fig.
4).
This
gives
the
circle
of
Willis
an
appearance
very
similar
to
that
of
the
orang-utan.
However,
this
rudimentary
vessel
goes
forward
only
to
the
frontal
pole,
and
does
not
curve
backward
over
the
genu
of
the
corpus
callosum.
Thus,
the
left
anterior
cerebral
usually
gives
rise
to
the
posterior
orbital,
the
anterior
orbital
and
the
anterior
frontal
arteries
to
the
left
hemisphere.
However,
in
fig.
4
the
anterior
orbital
is
seen
to
leave
the
left
division
of
the
main
artery.
Corresponding
arteries
to
the
opposite
side
originate
from
the
unpaired
trunk
described
above.
Each
terminal
of
the
unpaired
anterior
cerebral
artery
sends
a
middle
and
posterior
frontal,
a
superior
precentral
and
postcentral,
and
a
precuneal
branch
to
its
respective
hemisphere.
The
precuneal
artery
can
be
followed
into
the
parieto-
occipital
sulcus.
In
some
cases
a
small
twig
continues
along
the
sulcus
of
the
corpus
callosum
and
curves
over
the
splenium.
Often
there
is
no
anterior
communicating
artery
in
the
chimpanzee.
When
540
James
W.
Watts
a
communicating
artery
is
present,
it
is
a
short
thick
vessel
between
the
rudimentary
left
anterior
cerebral
and
the
large
anterior
cerebral
which
sends
branches
to
both
hemispheres.
In
one
brain
the
anterior
cerebral
arteries
run
antero-medially,
unite
and
enter
the
longitudinal
fissure
as
a
single
trunk.
This
large
trunk
supplies
branches
to
the
gyrus
rectus
and
the
orbital
parts
of
both
frontal
lobes
(fig.
5).
It
bifurcates
at
the
rostrum
of
the
corpus
callosum,
one
artery
running
on
the
medial
surface
of
each
hemisphere
close
to
the
body
of
the
corpus
callosum.
A
small
branch
continues
posteriorly
to
the
splenium.
The
sixth
specimen
presents
many
abnormalities.
A
relatively
large
com-
municating
branch
lying
under
the
posterior
part
of
the
optic
chiasm
connects
the
internal
carotid
arteries
(fig.
6).
From
this
vessel
arises
a
branch
which
Fig.
5.
Fig.
6.
Fig.
5.
Chimpanzee.
Like
fig.
4,
but
this
specimen
has
no
rudimentary
anterior
cerebral
artery.
Fig.
6.
Chimpanzee.
An
anomalous
arrangement
of
the
anterior
cerebral
arteries.
runs
anteriorly
under
the
chiasm
between
the
two
optic
nerves
and
anasto-
moses
with
the
anterior
cerebral
arteries.
The
right
and
left
anterior
cerebrals
anastomose
through
a
loop
composed
of
a
part
of
each
and
of
the
artery
which
passes
between
the
optic
nerves.
From
the
loop
a
large
single
artery
runs
forward
into
the
longitudinal
fissure
of
the
cerebrum.
It
bifurcates
at
the
rostrum
of
the
corpus
callosum
and
follows
the
course
already
described
in
the
other
specimens.
It
may
be
seen
that
a
relatively
large
branch
from
the
right
internal
carotid
lies
on
the
inferior
surface
of
the
right
optic
nerve.
A
prominent
branch
springs
from
each
side
of
the
loop,
and
corresponds
roughly
to
the
posterior
orbital
artery.
In
all
six
chimpanzees
which
have
been
described
the
two
anterior
cerebral
arteries
unite
at
the
entrance
of
the
longitudinal
fissure
of
the
cerebrum.
This
unpaired
artery
runs
forward
in
the
fissure
to
the
rostrum
of
the
corpus
callosum
where
it
divides
into
two
anterior
cerebral
arteries,
one
passing
along
Anterior
Cerebral
Artery
and
Circle
of
Willis
in
Primates
541
the
medial
aspect
of
each
hemisphere
close
to
the
corpus
callosum
supplying
cortical
branches
on
its
way.
In
four
of
the
specimens
a
second
anterior
cerebral
artery
arises
from
the
arterial
arch
to
the
left
of
the
main
trunk,
runs
forward
in
the
great
fissure
and
distributes
itself
as
far
as
the
frontal
pole.
The
circle
of
Willis
in
the
brains
just
mentioned
resembles
that
in
Man.
The
fifth
brain
shows
an
arterial
circle
which
is
similar
to
that
of
the
Cerco-
pithecidae.
In
the
sixth
an
anomalous
artery
arising
from
the
internal
carotid
arteries
joins
the
two
anterior
cerebrals.
From
the
site
of
the
anastomosis
of
the
three
arteries
arises
a
single
vessel
which
has
the
usual
distribution
within
the
longitudinal
fissure.
There
are
no
essential
differences
between
the
observations
made
upon
the
present
specimens
and
the
earlier
descriptions
of
the
circle
of
Willis
in
the
chimpanzee
which
have
been
found
in
the
literature.
Sperino
(1897)
found
the
superficial
cerebral
circulation
of
the
chimpanzee
similar
to
that
of
a
normal
man.
Grunbaum
and
Sherrington
(1902)
noted
that
the
arterial
circle
resembled
that
of
Man
in
four
specimens;
in
a
fifth
there
was
a
lateral
fusion
of
the
two
anterior
cerebral
arteries
at
the
usual
site
of
the
anterior
com-
municating
artery.
Rothmann
(1904)
examined
one
chimpanzee
brain
in
which
the
circle
of
Willis
was
like
that
of
Man,
another
which
had
two
anterior
cerebral
arteries
but
lacked
the
communicating
branch,
and
five
brains
which
had
the
type
of
circle
seen
in
the
Cercopithecidae.
Only
Shellshear
(1930)
and
Hindze
(1930)
have
described
the
distribution
of
the
anterior
cerebral
artery
of
the
chimpanzee
after
it
leaves
the
circle
of
Willis.
Shellshear
found
that
the
anterior
cerebral
artery
passed
antero-medially
to
the
commencement
of
the
longitudinal
fissure
where
it
joined
its
fellow
to
form
a
single
trunk.
The
unpaired
artery
extended
to
the
genu
of
the
corpus
callosum
and
divided
into
two
anterior
cerebral
arteries.
Hindze's
specimen
presented
a
large
right
anterior
cerebral
artery
which
supplied
parts
of
both
hemispheres
with
branches,
and,
in
addition,
had
a
rudimentary
left
anterior
cerebral
which
was
distributed
to
the
medial
surface
of
the
left
hemisphere
below
the
corpus
callosum.
V.
HYLOBATIDAE,
THE
LESSER
APES
Since
the
arteries
of
the
two
available
gibbon
brains
were
so
similar
to
the
Cercopithecidae
a
detailed
description
will
not
be
undertaken.
As
in
the
Cercopithecidae,
the
posterior
cerebral
arteries
are
formed
by
the
bifurcation
of
the
basilar
and
they
are
joined
to
the
internal
carotid
arteries
by
the
posterior
communicating
(fig.
7).
Likewise,
the
internal
carotid
artery
divides
into
two
terminal
branches,
the
middle
and
anterior
cerebral
arteries.
The
anterior
cerebral
artery
runs
antero-medially,
joining
its
fellow
of
the
opposite
side
to
form
a
single
trunk
which
enters
the
longitudinal
fissure
of
the
cerebrum.
Within
the
fissure
the
unpaired
artery
passes
forward
lying
close
to
the
rostrum
and
body
of
the
corpus
callosum.
From
one
brain
a
block
of
tissue
had
been
removed
which
made
it
impossible
to
follow
the
artery
through
its
entire
542
James
W.
Watts
length.
In
the
other
the
artery
continues
posteriorly
from
the
genu
giving
cortical
branches
to
both
hemispheres.
Bifurcation
of
the
main
trunk
occurs
in
the
posterior
third
of
the
corpus
callosum,
where
each
terminal
artery
divides
into
several
branches
distributed
to
the
medial
aspect
of
the
parietal
lobe.
A
small
vessel
continues
the
course
of
the
main
artery
along
the
corpus
callosum
to
the
splenium.
In
both
brains
the
right
anterior
cerebral
artery
is
better
developed
than
the
left,
being
twice
or
three
times
as
large.
The
arteries
of
only
a
few
gibbon
brains
have
been
described.
Waldeyer
(1891)
stated
that
the
arteries
of
the
base
of
the
gibbon
brain
are
essentially
like
those
of
Man.
According
to
Bertha
de
Vriese
(1905),
Sperino
(1898)
found
that
the
circle
of
Willis
of
the
gibbon
corresponded
in
all
particulars
with
that
of
Man.
However,
Rothmann
(1904)
noted
that
the
two
anterior
cerebral
Fig.
7.
Fig.
8.
Fig.
7.
Gibbon.
The
two
anterior
cerebral
arteries
unite
to
form
a
single
trunk
as
in
the
Cercopithicidae.
Fig.
8.
Macaca
mulatta.
The
two
anterior
cerebral
arteries
unite
at
the
entrance
of
the
longitudinal
fissure.
arteries
united
to
form
a
single
trunk
in
three
brains.
In
a
fourth
specimen,
instead
of
a
single
trunk,
two
arteries
arose
from
the
point
of
union
of
the
anterior
cerebral
arteries,
one
running
antero-laterally
to
the
right
and
the
other
antero-laterally
to
the
left.
The
anterior
cerebral
artery
and
the
circle
of
Willis
in
both
of
the
gibbon
brains
examined
here
belonged
to
the
type
found
in
the
Cercopithecidae.
VI.
CERCOPITHECIDAE,
THE
OLD
WORLD
MONKEYS
The
brain
of
the
Cercopithecidae
receives
the
usual
blood
supply
from
the
internal
carotid
and
basilar
arteries.
Branches
of
the
two
anastomose
to
form
a
polygonal
circle
of
Willis.
The
internal
carotid
artery
reaches
the
brain
between
the
tuber
cinereum
and
the
temporal
lobe,
curves
forward
3
or
4
mm.
and
divides
into
its
terminal
branches,
the
anterior
and
middle
cerebral
arteries.
The
internal
carotids
are
Anterior
Cerebral
Artery
and
Circle
of
Willis
in
Primates
543
usually
equal
in
size
and
symmetrical
on
both
sides.
A
small
posterior
com-
municating
artery
connects
the
internal
carotid
with
the
posterior
cerebral
artery
(fig.
8).
The
middle
cerebral
artery
runs
antero-laterally
into
the
fissure
of
Sylvius
and
forms
no
part
of
the
polygon.
Its
calibre
is
equal
to
that
of
the
anterior
cerebral
in
40
per
cent.
of
the
specimens,
is
larger
in
33
per
cent.
and
smaller
in
27
per
cent.
The
anterior
cerebral
artery
runs
antero-medially
toward
the
longitudinal
fissure
of
the
cerebrum
where
it
unites
with
its
fellow
of
the
opposite
side
to
form
a
single
vessel
which
passes
forward
into
the
fissure
(fig.
8).
There
is
no
anterior
communicating
artery.
Within
the
longitudinal
fissure,
the
unpaired
anterior
cerebral
artery
lies
close
to
the
rostrum
and
the
body
of
the
corpus
callosum,
sometimes
more
in
contact
with
the
medial
surface
of
one
hemi-
sphere
and
then
with
the
other.
It
sends
cortical
branches
to
the
medial
and
superior
surfaces
of
the
frontal
and
parietal
lobes
of
both
hemispheres.
There
are
an
equal
number
of
specimens
in
which
the
artery
divides
in
the
middle
third
of
the
corpus
callosum
and
in
which
the
division
occurs
in
the
posterior
third.
In
only
12
per
cent.
did
a
small
branch
continue
on
to
the
splenium
after
the
main
artery
bifurcated.
The
corresponding
branches
to
the
two
hemispheres
leave
the
anterior
cerebral
artery
close
together
but
not
always
opposite
each
other.
Not
infre-
quently
there
are
one
or
two
more
branches
to
one
hemisphere
than
to
the
other.
The
nomenclature
adopted
for
the
cortical
branches
of
the
anterior
cerebral
artery
of
the
Cercopithecidae
is
a
slight
modification
of
that
used
for
the
orang-utan
and
chimpanzee.
The
distribution
is
as
follows:
1.
Posterior
orbital-to
the
gyrus
rectus
and
posterior
part
of
the
orbital
gyri.
N
2.
Anterior
orbital-to
the
anterior
part
of
the
gyrus
rectus,
the
frontal
pole,
and
the
medial
surface
under
the
rostral
sulcus.
3.
Anterior
frontal-to
the
medial
surface
above
the
rostral
sulcus
and
to
the
frontal
pole.
4.
Middle
frontal-to
the
medial
surface
above
the
anterior
frontal
artery,
to
the
middle
part
of
cingulate
and
marginal
gyri,
and
to
the
superior
frontal
gyrus.
5.
Posterior
frontal
to
the
medial
surface
above
the
middle
frontal
artery,
to
the
cingulate
and
marginal
gyri,
and
the
superior
part
of
the
premotor
area.
6.
Parietal-to
the
posterior
portion
of
the
marginal
gyrus
and
the
superior
part
of
the
precentral
and
posteentral
gyri.
In
some
specimens
there
is
one
vessel
leaving
the
main
artery
and
in
others
there
are
two
branches
distributed
to
this
region.
7.
Precuneal-to
the
precuneous
and
the
superior
part
of
the
postcentral
gyrus,
often
to
the
interparietal
and
parieto-occipital
sulci.
In
12
per
cent.
of
the
specimens
examined
a
tiny
twig
continues
along
the
corpus
callosum
to
the
splenium
after
the
main
artery
bifurcates.
James
W.
Watts
The
posterior
cerebral
arteries
produced
by
the
bifurcation
of
the
basilar
run
laterally
a
short
distance
and
curve
posteriorly
around
the
cerebral
peduncles.
Through
the
first
part
of
its
course
the
artery
is
parallel
to
the
superior
cerebellar
artery
from
which
it
is
separated
by
the
oculomotor
nerve.
A
number
of
variations
of
the
anterior
cerebral
artery
are
worthy
of
note.
In
five
Macaca
mulatta
and
one
Papio
cynocephalus
the
arteries,
after
uniting,
redivide
to
produce
a
loop
(fig.
9).
In
three
specimens
the
loop
is
2-3
mm.
long
and
in
two
only
1
mm.
In
one
of
the
specimens
the
lumina
of
the
vessels
have
no
connection
in
the
proximal
part
of
the
loop.
In
four
Macaca
mulatta
and
one
Cercocebus
aethiops
the
anterior
cerebral
arteries
entered
the
longitudinal
fissure
as
separate
vessels
and
united
3-4
mm.
within
the
fissure
(fig.
10).
Fig.
9.
Fig.
10.
Fig.
9.
Macaca
mulatta.
After
union
of
the
anterior
cerebral
arteries,
the
main
trunk
divides
to
form
a
loop.
Fig.
10.
Macaca
mulatta.
The
right
and
left
anterior
cerebral
arteries
enter
the
longitudinal
fissure
separately,
and
unite
several
millimetres
within
it.
One
Macaca
mulatta
presented
a
picture
like
the
preceding
except
that
the
two
arteries
were
united
at
the
mouth
of
the
fissure
by
a
communicating
branch
(fig.
11).
This
gave
the
circle
of
Willis
a
form
closely
resembling
that
of
Man.
Two
specimens,
a
Macaca
mulatta
and
a
Cercocebus
aethiops,
show
a
rela-
tively
large
branch
leaving
one
anterior
cerebral
artery
before
it
joins
its
fellow.
This
branch
supplies
the
posterior
part
of
the
orbital
gyri,
thus
taking
over
some
of
the
function
of
the
first
branch
of
the
unpaired
trunk.
A
drawing
of
one
specimen
of
Ateles
ater
shows
this
quite
clearly
(fig.
12).
A
Papio
cynocephalus
has
a
similar
branch
originating
from
the
left
anterior
cerebral
artery
which
runs
forward
into
the
longitudinal
fissure
a
distance of
10
mm.,
crosses
the
mid-line
passing
over
the
common
trunk
and
sends
twigs
to
the
medial
surface
and
the
gyrus
rectus
of
the
opposite
side.
In
a
Cercocebus
aethiops
the
right
anterior
cerebral
is
unusually
large
and
544
Anterior
Cerebral
Artery
and
Circle
of
Willis
in
Primates
545
the
left
very
small
so
that,
although
the
two
unite
into
one
trunk,
nearly
all
of
the
blood
to
the
medial
surfaces
of
the
frontal
and
parietal
lobes
of
both
hemispheres
was
supplied
through
one
internal
carotid
artery.
A
Cercopithecus
sabeus
presents
a
similar
variation,
except
that
the
left
artery
is
much
the
larger.
The
Cercopithecidae
present
a
definite
type
of
arterial
circle.
The
anterior
cerebral
arteries
run
antero-medially,
unite,
and
enter
the
longitudinal
fissure
of
the
cerebrum.
Within
the
fissure
this
unpaired
artery
gives
rise
to
branches
distributed
to
the
medial
and
superior
surfaces
of
the
frontal
and
parietal
lobes
of
both
hemispheres.
Of
the
103
specimens
studied
seventeen
vary
a
little
from
the
usual
form.
The
variations
are
shown
in
figs.
9,
10,
11
and
12.
~~~~~~~~
~~~~~~~T
Fig.
11
Fig.
12.
Fig.
11.
Macaca
mulatta.
Similar
to
fig.
10,
with
the
addition
of
an
anterior
communicating
artery.
Fig.
12.
Atde8
after.
The
rudimentary
anterior
cerebral
artery
to
the
left
of
the
main
trunk
is
like
that
of
the
chimpanzee.
A
double
basilar
artery
joined
together
by
transverse
branches
is
characteristic
of
Atelei
ater.
In
no
specimen
did
the
two
arteries
extend
more
than
a
few
millimetres
into
the
fissure
before
uniting,
and
in
no
instance
did
this
unpaired
artery
bifurcate
before
reaching
the
middle
third
of
the
corpus
callosum.
As
quoted
in
the
Introduction,
Theile
(1852)
in
three
Simia
inuus
found
that
the
two
anterior
cerebral
arteries
united
to
form
a
single
trunk
which
gave
rise
to
branches
to
both
hemispheres.
Other
authors,
among
whom
are
Stannius
(1850),
Staderini
(1889),
Rojecki
(1889),
and
Lesem
(1905),
observed
that
the
two
anterior
cerebral
arteries
united
into
a
single
trunk
near
the
entrance
of
the
longitudinal
fissure
in
various
species
of
Cercopithecidae.
Rothmann's
(1904)
investigation
of
the
anterior
cerebral
artery
included
thirty-two
"niedere
Affen."
The
two
anterior
cerebral
arteries
united
into
a
Anatomy
LXVIII
35
James
W.
Watts
single
trunk
in
twenty
of
the
brains.
Five
other
specimens
showed
a
single
loop
in
the
unpaired
artery,
and
one
a
double
loop.
In
two
brains,
one
anterior
cerebral
artery
was
much
larger
than
its
fellow,
and
in
another
brain
one
anterior
cerebral
was
absent
so
that
the
medial
surfaces
of
both
hemi-
spheres
were
supplied
with
blood
through
a
single
internal
carotid.
Three
brains
showed
a
branch
leaving
the
first
part
of
one
anterior
cerebral
artery
making
the
circle
of
Willis
resemble
the
circle
of
the
chimpanzee
with
its
main
and
rudimentary
anterior
cerebrals.
Critchley's
(1930)
description
of
the
distribution
of
the
anterior
cerebral
artery
in
the
baboon
conforms
in
general
to
that
given
here.
VII.
CEBIDAE,
THE
NEW
WORLD
MONKEYS
Only
a
few
specimens
of
the
Cebidae
were
available
for
examination,
but
from
the
material
at
hand
it
would
appear
that
there
are
no
marked
differences
between
the
genus
Cebus
and
genus
Lagothrix
and
the
Cercopithecidae.
The
anterior
cerebral
arteries
unite
to
form
a
single
trunk
which,
within
the
longi-
tudinal
fissure,
has
branches
of
distribution
to
both
hemispheres.
The
circle
of
Willis
presents
the
usual
form
and
the
calibre
of
the
arteries
bear
the
same
relationship
one
with
the
other.
The
anterior
cerebral
arteries
unite
several
millimetres
within
the
longi-
tudinal
fissure
in
one
Lagothrix
(as
in
fig.
10).
In
another
Lagothrix
the
two
anterior
cerebral
arteries
are
joined
together
by
a
short
communicating
branch
at
the
entrance
of
the
longitudinal
fissure,
and
5
mm.
within
the
fissure
the
anterior
cerebrals
unite
into
a
single
trunk
(as
in
fig.
11).
Both
of
these
forms
are
seen
in
the
Cercopithecidae
and
considered
variations,
but
here
one
cannot
say
which
is
usual
and
which
unusual.
Certain
distinct
differences
are
present
in
the
Ateles
ater
which
were
not
seen
in
other
species
of
the
Cebidae
nor
in
the
Cercopithecidae.
A
slightly
different
method
of
presentation
will
be used
in
order
to
emphasise
their
significance.
After
reaching
the
intracranial
cavity
between
the
optic
chiasm
and
tem-
poral
lobe,
the
internal
carotid
artery
divides
into
two
branches,
an
anterior
and
a
posterior.
The
posterior
branch
runs
caudally,
approaching
its
fellow
of
the
opposite
side
as
it
nears
the
pons.
In
its
course
the
artery
gives
origin
to
a
collateral
branch
which
passes
anterior
to
the
oculomotor
nerve
and
curves
around
the
cerebral
peduncle.
This
branch
is
the
posterior
cerebral.
The
posterior
branch
of
the
internal
carotid,
the
posterior
communicating
artery,
continues
caudally
as
the
basilar,
which
is
double
(fig.
12).
The
basilar
arteries
are
parallel
from
the
upper
to
the
lower
margin
of
the
pons
where
they
diverge
and
continue
as
the
vertebrals.
In
their
parallel
course,
the
basilars
are
joined
together
by
a
transverse
anastomosing
branch
near
each
end.
One
specimen,
instead
of
anastomosis
by
transverse
arteries,
shows
a
lateral
fusion
of
the
basilars
for
a
distance
of
2
mm.
at
the
lower
and
4
mm.
546
Anterior
Cerebral
Artery
and
Circle
of
Willis
in
Primates
547
at
the
upper
level
of
the
pons.
In
another
specimen
there
is
a
fusion
for
5
mm.
at
the
upper
border
of
the
pons,
but
none
at
the
lower
border.
The
anterior
division
of
the
internal
carotid
artery
runs
antero-medially
to
unite
with
its
fellow.
This
unpaired
anterior
cerebral
artery
enters
the
longitudinal
fissure,
and
has
a
distribution
as
shown
in
fig.
9.
Before
its
union
with
the
opposite
anterior
cerebral
artery,
it
gives
origin
to
the
middle
cerebral
artery
which
passes
laterally
into
the
fissure
of
Sylvius.
There
is
considerable
individual
variation
of
the
anterior
cerebral
arteries
in
the
Ateles
ater
which
will
be
briefly
noted.
In
the
first
specimen
they
united
3-4
mm.
within
the
longitudinal
fissure.
In
the
second
there
is
a
small
loop
in
the
first
part
of
the
left
anterior
cerebral,
from
which
two
twigs
pass
diagonally
to
the
posterior
orbital
region.
In
the
third
specimen
there
are
two
anterior
cerebral
arteries
given
off
from
each
internal
carotid
(fig.
13).
The
larger
anterior
cerebral
arteries
unite
in
the
usual
way
at
the
lips
of
the
fissure;
the
smaller
';
N
arteries
curve
laterally
around
the
larger
and
join
/
the
unpaired
anterior
cerebral
artery
2
mm.
an-
\
terror
to
its
source.
The
arteries
of
the
fourth
brain
have
a
resemblance
to
the
circle
of
Willis
of
the
X
chimpanzee.
In
addition
to
the
typical
unpaired
h
artery
within
the
fissure,
a
branch
from
the
first
part
/
t/
/
of
the
left
anterior
cerebral
runs
forward
over
the
/
/
gyrus
rectus
almost
to
the
frontal
pole
(see
fig.
12).
Elze
(1910)
has
drawn
attention
to
the
double
)
basilar
artery
in
the
Ateles
ater
and
presents
ex-
cellent
diagrams
indicating
the
type
of
anastomosis
between
the
arteries.
In
half
of
his
specimens
the
basilar
arteries
were
joined
together
at
different
levels
by
transverse
branches
of
various
thick-
nesses.
In
the
fourth
there
was
a
short
lateral
basilar
is
like
that
in
fig.
12.
fusion
of
the
arteries
at
the
anterior
third
of
the
Two
anterior
cerebral
arteries
pons.
The
fifth
specimen
was
similar
to
the
fourth
from
the
right
unite
with
their
except
that
it
was
complicated
by
the
presence
of
fellows
of
the
left
near
the
entrance
of
the
longitudinal
a
loop
at
the
level
of
the
lateral
fusion.
The
sixth
cerebral
fissure.
had
a
single
basilar
artery
which
divided
to
form
a
loop,
but
otherwise
did
not
differ
greatly
from
the
basilar
of
other
species.
Although
an
occasional
loop
was
found,
a
double
basilar
artery
was
not
present
in
a
single
specimen
of
the
entire
series
of
125,
except
Ateles
ater.
VIII.
COMPARISONS
AND
CONCLUSIONS
For
purposes
of
comparison
with
the
other
Primates
it
may
be
permissible
to
say
here,
that
in
Man
the
anterior
cerebral
artery
arises
from
the
internal
carotid,
runs
antero-medially
and
enters
the
longitudinal
fissure.
Within
the
fissure
it
lies
on
the
medial
surface
of
the
hemisphere
close
to
the
rostrum
and
body
of
the
35-2
548
James
W.
Watts
corpus
callosum
and
sends
cortical
branches
to
the
frontal
and
parietal
lobes.
At
the
entrance
of
the
fissure
the
anterior
cerebral
arteries
are
connected
by
a
short
anterior
communicating
artery.
It
is
evident
from
the
descriptions
and
diagrams
presented
by
Rothmann
(1904)
in
two
cases,
and
by
Hindze
(1927,
1930)
in
two,
that
the
circle
of
Willis
and
the
anterior
cerebral
artery
of
the
gorilla
are
more
nearly
like
those
of
Man
than
any
other
Primate.
Next
to
the
gorilla,
the
arteries
of
the
orang-utan
resemble
those
of
Man
most
closely.
There
are
two
anterior
cerebral
arteries
in
all
of
the
orang-utans
in
this
series
and
in
all
described
in
the
literature,
except
one
observed
by
Rothmann
(1904)
and
one
cited
here,
both
of
which
had
three
arteries.
An
anterior
communicating
artery
connects
the
anterior
cerebrals
at
the
entrance
of
the
longitudinal
fissure
in
all
except
the
two
specimens
observed
by
Bolk
(1901)
in
which
the
communicating
branch
was
absent.
The
anterior
com-
municating
artery
of
the
orang-utan
differs
strikingly
from
that
in
Man
in
this
series
and
in
the
specimens
studied
by
Rothmann
(1904).
The
artery
has
a
diameter
as
great
as
that
of
the
vessels
it
unites.
The
two
anterior
cerebral
arteries
united
by
the
communicating
branch
form
an
arterial
arch
from
which
the
anterior
cerebral
arteries
which
enter
the
fissure
arise
at
right
angles.
Each
artery
supplies
the
medial
surface
of
the
frontal
and
parietal
lobes
of
its
respective
hemisphere
with
blood.
The
anterior
cerebral
arteries
of
the
chimpanzee
unite
at
the
entrance
of
the
longitudinal
cerebral
fissure,
run
forward
as
a
single
trunk
to
the
rostrum
of
the
corpus
callosum
where
the
trunk
redivides
into
two
branches,
one
going
to
each
hemisphere.
In
some
specimens
there
is
a
rudimentary
artery
arising
a
few
millimetres
to
the
left
of
the
common
trunk,
which
passes
forward
into
the
fissure
and
gives
branches
to
the
medial
surface
as
far
as
the
frontal
pole,
but
not
above
the
corpus
callosum.
The
same
distribution
of
the
arteries
was
found
by
Shellshear
(1930)
and
by
Hindze
(1930),
and
the
appearance
of
the
circle
of
Willis
in
five
of
Rothmann's
chimpanzees
indicates
that
union
of
the
two
anterior
cerebral
arteries
occurs
frequently.
There
were
two
anterior
cerebral
arteries
connected
by
a
communicating
branch
in
four
specimens
examined
by
Grunbaum
and
Sherrington
(1902).
These
authors
made
no
observations
on
the
course
of
the
arteries
within
the
longitudinal
fissure.
It
would
appear
that
the
anterior
cerebral
artery
and
the
circle
of
Willis
of
the
gibbon
resemble
the
human
type
in
some
specimens
and
the
Cerco-
pithecidae
type
in
others.
Sperino
(1898)
and
Waldeyer
(1891)
found
the
arrangement
of
the
arteries
was
similar
to
that
of
Man;
in
this
series
and
in
Rothmann's
(1904)
the
type
was
found
to
be
similar
to
that
seen
in
the
Cercopithecidae.
A
sufficiently
large
number
of
Cercopithecidae
have
been
examined
to
say
that
in
this
family
the
anterior
cerebral
artery
runs
antero-medially
toward
the
longitudinal
fissure
of
the
cerebrum
where
it
unites
with
its
fellow
of
the
opposite
side
to
form
a
single
vessel
which
passes
forward
into
the
fissure.
There
is
no
anterior
communicating
artery.
Within
the
fissure,
this
unpaired
Anterior
Cerebral
Artery
and
Circle
of
Willis
in
Primates
549
artery
lies
close
to
the
rostrum
and
body
of
the
corpus
callosum,
and
sends
cortical
branches
to
the
medial
-and
superior
surfaces
of
the
frontal
and
parietal
lobes.
Certain
variations
in
the
course
of
the
anterior
cerebral
artery
have
been
observed.
The
contributions
of
Stannius
(1850),
Theile
(1852),
Staderini
(1889),
Rojecki
(1889),
Rothmann
(1904),
Lesem
(1905),
and
Critchley
(1930)
confirm
the
observations
on
the
anterior
cerebral
artery
and
circle
of
Willis
which
were
made
in
the
present
study.
The
genus
Cebus
and
genus
Lagothrix
of
family
Cebidae
conform
to
the
type
established
for
the
Cercopithecidae.
Likewise,
except
for
marked
indi-
vidual
variations,
the
anterior
cerebral
artery
of
the
specimens
of
Ateles
ater
belong
to
this
type.
However,
a
most
striking
characteristic
differentiates
the
Ateles
ater
from
the
other
species
examined,
that
is,
the
presence
of
a double
basilar
artery.
The
double
basilar
was
present
in
all
individuals
of
this
species
but
was
not
present
in
a
single
specimen
in
the
entire
remaining
125
Primate
brains.
Elze
(1910)
has
previously
called
attention
to
the
double
basilar
artery
in
the
Ateles
ater.
The
family
differences
as
well
as
the
individual
variations
become
more
easily
understandable
in
light
of
the
excellent
work
of
Bertha
de
Vriese
(1905).
She
made
a
careful
study
of
the
literature
relating
to
the
cerebral
arteries
of
many
lower
animals,
and
herself
examined
a
series
of
human
embryos
and
the
embryos
of
lower
animals.
She
found
that the
internal
carotid
artery
is
more
primitive
than
the
vertebral,
and
that.the
carotid
supplies
the
entire
brain
in
the
early
stages
of
embryonic
life.
It
divides
into
a
large
cranial
and
a
large
caudal
branch.
The
anterior
cerebral
artery
is
a
continuation
of
the
cranial
branch
and
the
middle
cerebral
is
a
collateral.
In
the
early
stages
of
embryonic
life
the
anterior
cerebral
arteries
run
parallel
to
each
other
without
a
connection
between
them.
They
become
united
by
a
communicating
network
from
which
arises
a
median
artery
which
can
become
the
unpaired
anterior
cerebral
artery.
In
animals
having
a
single
artery
the
lateral
arteries
atrophy.
In
species
which
have
parallel
anterior
cerebral
arteries
it
is
probable
that
the
median
artery
atrophies.
Bertha
de
Vriese
(1905)
also
determined
that
primitively
the
basilar
artery
is
the
termination
of
the
caudal
branch
of
the
internal
carotid,
and
in
the
early
stages
the
basilar
is
double.
Transverse
anastomosing
vessels
develop
and
later
loops
are
found
along
the
course
of
the
two
basilar
arteries;
and
finally,
through
further
development
in
some
places
and
atrophy
in
others,
an
unpaired
basilar
artery
results.
The
posterior
cerebral
artery
is
a
collateral
of
the
caudal
branch
of
the
internal
carotid,
and
the
small
posterior
communi-
cating
artery
is
all
that
remains
of
the
caudal
branch.
I
am
deeply
indebted
to
Dr
John
F.
Fulton
for
placing
his
valuable
material
at
my
disposal
and
for
his
many
criticisms
and
suggestions.
I
also
wish
to
thank
Mrs
Frances
C.
Woodhall
and
Mr
Armin
Hemburger
for
the
interest
and
care
they
have
taken
in
the
execution
of
the
drawings.
550
James
W.
Watts
REFERENCES
BEEVOR,
C.
E.
(1909).
"
On
the
distribution
of
the
different
arteries
supplying
the
human
brain."
Phil.
Trans.
Roy.
Soc.
vol.
cc,
p.
1.
BOLK,
L.
(1901).
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