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Observations on the ductus arteriosus of the guinea pig in relation to its method of closure.

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OBSERVATIONS ON T H E DUCTUS ARTERIOSIJS O F
THE GUINEA P I G I N RELATION TO ITS
METHOD O F CLOSURE
J. ALLEN KENNEDY AND SAM L. CLARK
Departments of Nedzctne and Anatomy, Vanderbzlt Unzwersaty School of Nedzcin?,
Nashvzlle. Tennessee
FOUR P L A T E S (FOUBTEEN F I G U R E S )
The closure of the ductus arteriosus at birth establishes an
adult type of pulmonary circulation by abolishing the sliunt
of blood from the pulmonary artery to the aorta. Failure of
this closure constitutes one of the common forms of congenital
heart disease, patent ductus arteriosus, the importance of
which is apparent.
I n the published work on the ductus arteriosus several
theories have been proposed to explain the niechanisni of its
closure. Wells in 1908 summarized the more important of
these as follows: the first expansion of the large bronchi by
air compresses the ductus arteriosus ; thrombosis in its lumen
and subsequent adhesion of the walls closes the ductus ; bending of the arch of the aorta by increased pressure after birth
causes closure; beginning of respiration causes a change in
position of the thoracic viscera and this causes tension and
collapse of tlie ductus; fibrous growth in the intima leads to
occlusion; active contraction of the layers of the wall of the
ductus closes it; fibrous bands passing over the ductus a r e
connected with the diaphragm and upon descent of the diaphragm with respiration the bands a r e pulled down and occlude
the ductus; a thin crescentic fold of tissue present a t tlie aortic
end of the ductus acts like a valve in preventing the flow of
blood from the aorta into the ductus.
349
350
J. ALLEN KENNEDY AND S A M L. CLARK
Wells clearly understood the problem and set forth the
conditions which a theory of closure must satisfy t o be valid.
He stated (p. 388) that closure of the ductus
“is a physiological process taking place spontaneously and
instantaneously in every newborn child, and theref ore there
must be some mechanism which can be relied upon always to
perform this occlusion. Any explanation which involves connective tissue proliferation must be inadequate, for the duct
is patent and carrying on its full function up to the moment
of delivery, and then is at once occluded when the child begins
to breathe; it is necessary to distinguish between the instantaneous occlusiorz of the duct and its subsequent obliteratioit.”
In searching for experimental work to support the various
theories it was found that the microscopic anatomy of the
ductus has been well studied, but little experimental work has
been done with a physiological approach. I n the literature
we were unable to find any work recording direct observation
of the closure of the ductus arteriosus except that of Barcroft,
Kennedy and Mason ( ’38) who observed closure of the exposed
ductus in fetuses still attached to the placenta.
The only other work bearing on the subject are indirect
obserrations made by Barclay, Barcroft, Barron and Franklin
(’38). These workers injected opaque media into the blood
stream of sheep fetuses near term and by serial x-ray plates
observed the closure of the ductus arteriosus. By this method
it was found that in the two fetuses in which the ductus was
observed open when first seen on the serial x-ray plates, closure
occurred at 45 seconds and 56 seconds following delivery of
the fetus. I n three others it closed between the time of deliver? and the time of taking the first plates which began at
39 seconds, 1 minute 20 seconds, and 1 minute 12 seconds,
respectively after delivery. I n a second paper these authors
point out that their identification of the shadow of the ductus
was in error, therefore casting doubt on the validity of the
preceding data. I n this paper (’39) they re-identified the
CLOSURE OF DUCTUS ARTERIOSUS
351
ductus in new films and state (p. 512) that “according to our
records, the ductus closes functionally shortly after delivery. ”
Having become interested in the ductus arteriosus we have
been attempting to correlate and confirm the anatomical facts
and t o explore the physiological reactions relative to its
closure. We have observed that the process of normal closure
consists of two separate mechanisms or phases. The first is
a rapid or immediate closure which takes place within a few
minutes following birth. This process appears to be analogous
to contraction of a smooth muscle sphincter and results in
complete functional closure (with obliteration of the lumen at
one o r more points). Following this, the second and much
slower phase begins which is concerned entirely with histological changes in the wall of the ductus. The lumen remains
closed and the wall is transformed gradually over a period of
weeks o r months from a predominantly muscular one to a
fibrous connective tissue cord or ligament. The present report
is concerned with the characteristics of these two phases of
closure of the ductus.
METHOD
I n . the present experiments sixty-one normal pregnant
guinea pigs near term were used, and were prepared for
experiment in three different ways. They were kept under
ether during the entire experiment; or else kept under ether
a short period while they were decerebrated, or while the
spinal cord was being transectod in the middle thoracic region.
I n order to simulate intrauterine conditions for the fetuses
as closely as possible the pregnant guinea pigs were placed
during the experiment in a bath of physiological saline maintained approximately at body temperature. The lower half
of the adult animal from the chest dowii was kept constantly
beneath the surface, the uterus was delivered through an
opening in the abdomen, and one fetus at a time was carefully
removed through an incision in the uterine wall, leaving its
placental attachment by the umbilical cord intact. A skin clip
was used to close partially the opening in the uterine wall so
352
J. ALLEN KENNEDY AND SAM L. C L A R K
a s to prevent extrusion of the placenta. I n this way the fetuses
were kept warm, were prevented from breathing air, were able
to maintain exchange of gases through the placenta and remained in a lively state for as long a s several hours. Under
these conditions the fetuses could be utilized in a leisurely
manner and subjected to various experimental procedures.
I n preparing a fetus for experiment a portion of the chest
wall was removed in order to see the ductus arteriosus clearly.
I n the guinea pig fetus the ductus is about 3-4 mm. i n length,
and when open is approximately the same size as the pulmona r y arterial trunk before its bifurcation. I n fact, from the
ventral aspect, it appears to be a continuation of the pulmonary artery without obvious diminution in size or change in
direction, joining the aorta at approximately a 40" angle.
OBSERVATIONS
The difference between a n open and a closed ductus arteriosus can easily and readily be decided by direct observation.
Since this point is of prime importance we present figures to
illustrate it (figs. 1, 2, 3, 4, 5, 6).
Under the conditions of the experiments in the normal fetal
state the ductus arteriosus was always open as far a s we .have
observed. I f a fetus was allowed t o lie in the warm saline bath
attached to its umbilical cord and placenta, the ductus arteriosus remained open and unchanged for hours. However, in
response to certain definite stimuli the ductus promptly closed,
its diameter becoming much smaller, the wall paler, while the
flow of blood through it ceased entirely. It had the appearance
of having undergone muscular con traction. Following this,
with cessation of the stimulus which precipitated closure, the
ductus was observed to open again. This sequence of closing
and opening could be repeated a t will several times in the same
ductus, tlins allowing successive observations in the same animal under various experimental conditions.
Several types of stimuli could precipitate closure of thc
ductus in our preparations. Closure occurred if the fetus was
allowed to breathe before opening the chest wall. This closure
CLOSURE OF DUCTUS ARTEHIOSUS
353
took place with the placental circulation either intact or interrupted. After opening the chest, an open ductus was observed
to close following rhythmic inflation of the fetal lungs through
a tracheal canula (figs. 3,4) (the placental circulation remaining intact) and this was the method employed when repeated
closures of the same ductus were desired. The ductus could
also be made t o close by weak electrical stimulation applied
directly to its wall or by mechanically pinching its wall witli
tissue forceps.
The time of closure following normal birth is of considerable importance. We have examined the ductus arteriosus
grossly and microscopically in serial sect.ions in normal newborn guinea pigs at short intervals from a few minutes after
birth, up t o the age of 31 days. I n every case the ductus
arteriosus has appeared completely closed. From these and
other observations it seemed probable that closure of the
ductus has a close relationship to the onset of breathing. In
an effort to determine as nearly as possible the time required
for closure, a series of fetuses was examined at short intervals
after the onset of breathing in the following manner. The
fetuses were removed from the uterus and allowed to lie
quietly beneath the surface of the saline bath, under which
co:iditions the ductus arteriosus has been found to remain open
indefinitely. Each fetus was then raised to the surface, its
urnbilical cord was clamped, and it was allowed t o breathe.
At different intervals after the onset of respiration the chest
was quickly opened (which can be done in 15-20 seconds) and
the state of closure of the ductus observed.
By this technique it was found that in active, well developed
fetuses the ductus arteriosus was always closed when examined between 4 and 10 minutes following the onset of effective
respiration. Within 1to 3 minutes after beginning respiration
it was usually found in a state of partial closure. There is,
of course, the possibility that opening the chest in itself influenced the ductus t o close. However, except in a few instances,
it was found that in more than 100 fetuses when the chest was
opened by similar technique without allowing air to enter the
354
J. ALLEN KENNEDY AND SAM L. CLARK
lungs, the ductus arteriosus was open. I n the fern exceptions
in which the ductus was found partly or completely closed
when the chest was first opened there were other factors present which could have been responsible for closure.
Histological changes associated w i t h permanent closure. A
number of papers have been written covering the histological
structure of the ductus arteriosus and references in the literature may be found as f a r back as Billard in 1828. The interest
of most authors has been concerned with the structure in relation to its closure after birth. Warren, while making a study
of blood vessel healing, recorded the histological appearance
of the ductus arteriosus both before and after birth. H e found
that it had a different structure from other portions of the
arterial system. This he described a s mainly due to the great
thickness of the inner coat, and the indistinctness of the different coats of the wall. I n the ductus after birth he noted
that the walls, except for the advcntitia, underwent a marked
change which appeared to Be hyaline degeneration. This was
followed by a n active cell proliferation and tlie vessel was
gradually transformed into a fibrous ligament.
I n 1920 Variot and his colleagues made a similar study.
Tlicy stressed the importance of tlie area of degeneration in
the wall following birth, and of the “embryonic cclls” and
later fibroblasts which appeared in this area preceding its
transformation to a fibrous cord.
Schaeffer in 1914 described in the ductus after birth an
extensive hypertrophy of the inner elastic membrane and to
a less extent of the elastic tissue of the media and adventitia.
He stated further that the elastic tissue formed a large part
of the tissue which eventually occluded the ductus.
Von Hayek in 1935 pointed out the importance of the architecture of the layers of the tissue in the ductus especially the
bundles of smooth muscle fibers which he described as being
arranged in an oblique or spiral fashion.
IIarman and Herbertson in 1938 described changes in the
ductus of newborn guinea pigs and found that closure was
“effective on the third day after birth.” While they found
CLOSURE O F DUCTUS AKTEKIOSUS
355
soiiie variation in the lumen after 3 days, they state that tlie
ductus has the appearance of a solid cord by the secoiid o r
third week.
Swenson ('39) in a recent paper which appeared while our
work was in progress, gave a good sunimary of the older
literature. On the whole his histological description does not
differ from others except in details. After consideration of
some of the theories of closure that liave been given by various
workers lie suggests t h a t in closure of the ductus there are
both active and passive factors.
Our own work on the histology of the ductus has consisted
in studying serial sections of tissue removed from guinea pigs
representing ages from the last week of fetal life to 31 days
after birth. The histological appearance of the various specimens was studied following staining of successive sections
f r o m a series with hematoxylin a n d eosin, Rlallory 's triple
stain for connective tissue, and Weigert's stain for elastic
fibers. The guinea pig is suitable for study of this k i d because the ductus is changed from a vessel with a muscular
wall to a fibrous connective tissue ligament in about 1month
(figs. 10, 11). Since this study on the whole confirms previously published work, only a summary will be given, tracing
the main changes which take place.
During late fetal life the ductus has a characteristic appearance and is distinctly different in structure from the pulmonary artery or aorta. Compared with these vessels the
ductus arteriosus has a niuch thicker but looser wall containing relatively more sniooth muscle and less elastic and collagenous tissue (figs. 5, 9) , a thicker intima and lumen of about
tlie same size. The media is made predomiiiantly of sinootli
muscle bundles ai*ranged loosely with irregular spaces hetween them and while their general arrangement is in a circul a r direction there is a strong tendency for some of them to
run obliquely. There is a fairly abrupt transition in histological appearance a t the points of junction between the ductus
and the adjoining vessels, because of the large amount of
smooth muscle in the ductus and the proportionately smaller
356
J. ALLEN KENNEDY AND SAM L. CLARK
amount in the great arteries. The reverse is true of the elastic
and collagenous tissue. The adventitia is essentially the same
as that of the great arteries.
Soon after birth the lumen of the ductus arteriosus is ohliterated. I n every specimen obtained after normal birth and
examined histologically, each cut in serial sections, the lumen
has been completely obliterated at some point. I n other words,
following its closure immediately after birth the lumen of the
ductus arteriosus remains closed.
I n the days following birth there occur profound histological changes which transform the ductus into a fibrous ligament
(figs. 1 0 , l l ) . These changes involve predominantly the intima
and the central part of the media which apparently degenerate
and are replaced first by a homogeneous, relatively acellular,
substaiice and later by collagenous and elastic tissue fibers.
The outer part of the media and the adventitia undergo mucli
less change. There is a gradual disappearance of smootli
muscle which is replaced by fibrous connective tissue.
The first signs of degeneration are found about the third
day in the intima and central half of the media. Ry the fourth
and fifth days the degeneration is well marked and hp the
seventh day the degenerated area u7hich now occupies a large
central part of the ductus is replaced by a homogenous acellular substance. Collagenous fibers have begun to increase by
the fifth day and have greatly increased by the seventh day.
Somewhat later elastic tissue fibers similarly increase. The
homogenous material gradually becomes organized during the
tenth to fifteenth day, begins to disappear, and by the twentysecond day has disappeared. Most of the smooth muscle has
disappeared by the fifteenth day and tlie collagenous and
elastic tissue predominates. The fibrous tissue is arranged
in loose longitudinal bundles by the twenty-second day and the
ductus is seen to be smaller in diameter. By the thirtp-first
day it has approached the structure of a fibrous cord, though
some smooth muscle is recognizable in the media (fig. 11).
Nerce fibers and endings irz the wall of tlae d u c t m . At
special points in the walls of some of the great vessels near
CLOSURE O F DUCTUS ABTEBIOSUS
357
the heart there are found elaborate terminations of nerve
fibers, and nearby are small epithelioid bodies (paraganglia)
which are also rich in innervation. The wall of the aorta just
cranial to the opening of the embryonic ductus arteriosus is
infiltrated with the terminations of the aortic (depressor)
nerve. This region has been adequately described most recently by Nonidez (’35a and b) who states that his findings
largely corroborate those of Tello in embryos. With the nearness of the ductus arteriosus it is not surprising that the nerve
fibers to the area have at least a relation to this structure.
Nonidez (’37) found in the dog that the nerve to the aorta
from the left cardiac nerve supplied pressoreceptor endings
to the externa and outer third of the media of the aorta. He
found that the nerve itself did not end there, but ran onto the
anterior surface of the ductus arteriosus to reach the (p. 304)
“anterior aspect of the bifurcations of the pulmonary trunk,
forming a second pressoreceptor area, not present in the rabbit and cat although in these animals there are pressoreceptor
endings in the wall of the ductus arteriosus.” Goormaghtigli
and Pannier ( ’39) illustrate nerve endings in the aorta near
the attachment of the ductus arteriosus, and figure in diagram
sensory endings on the ductus itself. They state they have
confirmed findings of Takjno and Watanabe ( ’37) that nerve
endings are present in the ligament of Botal.
I n serial sections of the region about the heart and great
vessels of fetal guinea pigs near term stained with Ranson’s
pyridin silver method, we have been able t o confirm in general
the descriptions given by Nonidez. The aortic depressor area
in our preparations, as recognized by elaborate branching
and ending of nerve fibers, spread from a region of greatest
density on the antero-medial portion of the aorta just cranial
to the junction of the ductus arteriosus until it almost surrounded the aorta at this level (fig. 1 3 ) . Some of the endings
spread into the wall of ductus a t its aortic end (figs. 12, 14),
and yet it appeared obvious that the center of the area was
in the aortic wall, where nerve terminations occurred in all
layers even reaching the intima. While a comparable area of
358
J. ALLEN R E N F E D Y A K D SAM L. CLAHR
nerve endings was seen infiltrating the walls of the right subclavian artery near its origin, no elaborate endings were found
in the pulmonary artery. The nerve fibers reaching the ductus
from this aortic depressor area appeared to have been derived from myelinated fibers.
I n other regions of the ductus a s on the ventral surface or
near the junction with the pulmonary artery a few fibers of
finer calibre suggesting unmpelinated postgangionic efferents
were found. There were not enough of these to consider them
suficient f o r innervation of the smooth muscle of the ductus
~7all,perhaps. It may be there were more which were unstained. The soiirce of these fibers was apparently the bundles
of unmyelinated fibers which abound in the immediate neighbor21oocl, and which belong to the cardiac nerves and plexuses.
DISCUSSION
The conception of two separate phases of closure of the
ductus arteriosus helps t o rationalize some of the confusing
theories and observations made in the past. During late fetal
life the wall of the ductus is predominantly muscular. Its
muscular fibers a r e mainly circular, but have a strong tendency toward an oblique o r perhaps spiral arrangement. This
structure should be well suited for closure by muscular contraction, and a spiral arrangement of the muscular fibers
might aid in sustaining closure. Direct observation of closure
of the ductus and especially the successive closure and opening
of the same ductus speak strongly for muscular contraction
a s the means of immediate closure.
Normally, the initial closure takes place within a period of
a few minutes following birth. A fairly complex series of
histological changes then occurs involving mostly the intima
and inner media, but eventually the whole ductus is changed
from a muscular walled tube to a fibrous connective tissue
ligament.
The cause of these histological changes offers an interestiiig
subject for speculation. Vasa vasorum a r e present, at the
time of birth, in the outer p a r t of the media, according to
CLOSURE O F D U C T U S ARTERIOSUS
359
Winternitz, Thomas and Le Compte ( '38). That portion of
the ductus which lacks these vessels is the same portion in
which the most marked degeneration takes place. It may be
that after closure of the lumen of the ductus, the central part
is no longer able to obtain a supply of blood through either
vasa vasorum or the lumen and as a result of this it deg
0 enerates. If this is true, the precipitating cause of the histological
changes could be a lack of blood supply brought on by muscular contraction of the wall. MTinternitz,Thomas and Le Compte
found many tiny vessels in the intima and media of the ductus
in infants of 2 to 4 months of age. By this time the organization of the ductus into a fibrous cord is well along. Gerard
('00) observed vasa vasorum in the adventitia only of the
ductus of newborn humans.
The presence of nerve fibers in the wall of the ductus is an
interesting fact though we are unable to say what their function is. Those which come from the fibers of the aortic depressor area suggest that they were merely sprouts which
extended into neighboring territory in accordance with the
tendency of growing nerve fibers to extend along objects like
vines growing upon a trellis, a principle emphasized by Cajal
( '28) and others. The nerve fibers of fine unmyelinated variety
in other portions of the ductus sugyest an innervation of
muscle fibers, but their small number is against this. The fact
that closure of the ductus follows inflation of the lungs suggests a reflex pathway, but the effector muscle might be
activated by a hnmoral substance released at some remote
point or respond to some mechanical stimulus.
The importance of the valve-like fold of tissue at the aortic
end of the ductus referred to earlier must be evaluated. Cohnh i m and Zuntz (1888) and later Strassman (1894) were
apparently the first workers to describe this structure and
attempt to relate it to closure of the ductus. It was thought
that a thin crescentic fold was formed at the angle of insertion
of the ductus into the aorta. Such a fold has been described
in late human fetuses and those of several other species. The
theory of closure depending on a flap-like valve states that
360
J. ALLEN KENNEDY AND SAM L. CLARK
during fetal life blood flows from the pulmonary artery
through the ductus into the aorta, but after breathing the
pressure in the pulmonary arterial system is lowered and
blood flow then tends to go from aorta to pulmonary artery.
The crescentic fold prevents this flow by its valve-like action,
thereby stopping blood flow through the ductus. Following
cessation of its function the ductus then undergoes involution.
More recent advocates of this theory a r e Hamilton, WoodburF and Woods. To quote (p. 210): “ I n dogs and rabbits,
a t least, the ductus arteriosus is valve-like. There is a pair
of flaps (rabbit) or a single flap (dog) which a r e competent
to stop back flow of perfused saline from aorta to ductus but
allow it free flow from ductus to aorta.” (p. 211) : “Conditions
in the human fetus a r e different in that blood may flow either
way in the ductus arteriosus. There a r e no valve-like flaps to
guard the aortic opening of the human ductus.”
The theory of closure expressed by these authors places the
valve-like fold in a position of prime importance in the mechanism. However, if such a valve does not occur i n all species
it would be necessary to assume there was more than one
mechanism of closure. Hamilton e t al. admit such a valve does
not occur in the human ductus, though Rehman (’40) has
described a ridge or valve projecting into the lumen of the
ductus “ a t varying distances from the pulmonary end.” The
ridge involved the intima and media and was found in 99%
of the 142 late human fetal and newborn specimens studied.
Harnian and Herbertson found no valve-like structure in
guinea pigs.
I n guinea pig fetuses near term we have observed a small
fold or projecting lip at the junction of the walls of the ductus
and aorta. This lies at the superior o r cephalic side (figs. 7, 8)
and has almost the thickness of the adjoining arterial walls.
I t projects toward the lumen of the ductus as well as into the
lumen of the aorta but appears too short to occlude the ductus.
I n the guinea pig fetus this structure seems inadequate to
obstruct the flow of blood from the aorta into the ductus and
does not correspond in position to the valve in the human
CLOSURE OF D U C T U S ARTERIOSUS
361
ductus described by Rehman. Accordingly, wc do not believe
that it is a n importaiit factor in closure of the ductus in this
species. Comparison of the structure with the sketch shown
by Hamilton, Woodbury and V o o d s suggests that in the guinea
pig it is little more than the lip formed by the acute angle of
insertion of the ductus into the aorta. Our figure 8 resembles
the junction of the mesenteric artery with the aorta shown
by these authors more than it does their illustration of the
opening of the ductus into the aorta. The evidence from our
experiments is in favor of muscular contraction of the wall
of the ductus as the mecliaiiism of closure.
The present study has a close bearing on the problem of
patency of the ductus arteriosus. I n view of the evidence
whiclA has been presented it is possible that this form of congenital heart disease could be due to failure of the normal
physiological mechanism of closure rather than to a malforniation o r a developmental anomaly.
SUMMARY AND CONCLUSIONS
1. The ductus arteriosus of the fetal guinea pig has in its
walls more smooth muscle and less elastic and collag0 enous
tissue than the aorta and pulmonary arteries.
2. Following normal respiration, artificial inflation of the
lungs, or certain other stiinuli the ductus of fetal guinea pigs
near term can be seen to closc within a few minutes, apparently by muscular contraction. If the fetus is left attached to
the placenta and inflation of the lungs stopped, the ductus will
open again after a few minutes. The same ductus can be seen
repeatedly to close and open under the proper conditions.
3. Following closure of the ductus by muscular contraction
a t normal birth there occurs a series of changes in which the
muscle in the wall is replaced by connective tissue and the
ductus becoines a fibrous ligament.
4. Nerve fibers and endings have been found in the wall of
the ductus but these appear to be incidental t o the location
of the ductus, and the evidence is not sufficient to interpret
their function.
362
J. ALLEN KENNEDY A N D SAM L. CLARK
LITERATURE CITED
BARCLAY,
A. E., J. BARCROFT,
D. H. B-4R.RON -4ND K. J. F R A N K L I N 1938 X-ray
studies of the closing of the ductus arteriosus. Brit. J. Radiol., vol. 11,
pp. 570-58R.
1939 Radiographic demonstration of circulation through heart in
adult and in fetus, and identification of ductus arteriosus. Brit. J.
Radial., V O ~ . 12, pp. 505-517.
BARCROFT,
J., J. A. KENNEDY
AND M. F. MASON 1938 The relation of the vagus
nerve to the ductus arteriosus in the guinea-pig. J. Pliysiol., vol. 92,
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BILLARD,
C. M. 1828 Trait6 des maladies des enfants nouveau-n6s
et h la
mamelle, fond6 sur de nouvelles observations cliniques et d ’anatomie
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D , 1900 Le Canal Arteriel. J. de l’Anatomie, vol. 36, pp. 1-21.
GOORXAGHTIGH,
N., AND R. PANNIER
1939 Les paraganglions du coeur et des
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HAJIILTOX,
W. F., R. A. WOODBURY
AND E. R. WOODS 1937 The relation between
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H A R ~ I I A N ,1\1. T., AND J. E. HERBERTSON
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and the ductus arteriosus in the guinea pig. Trans. Kansas Acad.
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NONIDEZ,
J . F. 1935 Observations on blood supply and t h e innervation of the
aortic paragnnglion of the cat. J. Anat., vol. 70, pp. 215-225.
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body, the glomus aorticum. Am. J. Anat., vol. 57, pp. 259-291.
-___
1937 Distribution of the aortic nerve fibers and the epithelioid
bodies (supracardial ‘paraganglia’) i n the dog. Anat. Rec., vol. 69,
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R.4116~Y CAJAL, S. 1928 Degeneration and regeneration of the nervous system.
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REH3L4N, IRVING 1940 A study of the microscopic anatomy of the ductus arteriosus and further findings regarding the frequency and the structure of
the “valve of the durtus arteriosus.” Annt. Rec., vol. 76, suppl. no. 2,
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SCIIXEFFER, J. P. 1914 The behavior of elastic tissue in the post-fetal occlusion
and obliteration of the ductus arteriosus (Botalli) in Sus scrofa. J.
Exper. Med., vol. 19, pp. 129-143.
1914 Behavior of elastic tissue in post-fetal occlusion and ultimate
obliteration of certain blood vessels. Anat. Rec., vol. 8, pp. 96-97, Proc.
STRASS~IANN,
P. 1894 Anatomische und physiologische TJntersuchungen iiber
den Blutkreislauf beim Keugebornen. Arch. f. Gynaekologie, vol. 45,
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CLOSURE O F DUCTUS ARTEFXOSUS
363
SWENSON,
A . . 1939 Beitrag zur 1Gmntnis von dem liistologischen Bau und dem
postembryonalen Verschluss des Ductus Arteriosus Botalli. Zeitschr.
f. Mikr. Anat. Forsch., vol. 46, pp. 2 7 5 2 9 8 .
TAKINO, M., AND 8. WATANABE 1937 Uber die Bedeutung des Ligamentuin
Arteriosum bzw. des Ductus Botalli und der ansatzstelle desselben a n
der Pulmonalwand (A. Pulm.) Als Blutdriickzugler bei Verseheidenen
Tierarten.. Arch. f . Kreielaufforsch., vol. 2, pp. 18-27.
TELLO,J. F. 1924 Developpement et terminaison du nerf dbpresseur. Trav. Labor.
Rech. Biol. Univ. Madrid, T. 22, p. 293. (From Nonidez bibliog.)
VARIOT,G., AND F. CAILLIAU 1920 Recherches sur le processus d’obliteration du
canal arthriel. Eulletins e t MBmoires de la SOC.MBd. des HBpitaux de
Paris 44, pp. 1598-1604.
VARIOT,
G., AND BRZEZICKI 1921 Recherehes sur le mode d’obliteration du canal
arteriel. Arch. de MBd. des Enfants, vol. 24, pp. 537-548.
VON HAYEK,H. 1935 Der funktioiielle Bau der Nabelarterien uiid des Ductus
Botalli. Ztschr. f. Anat. u. Entwcklngsgesch., vo1. 105, pp. 15-24.
WARREN,
J. C. 1886 The healing of arteries. New York, Wm. Wood & Po.
WELLS,
H. G. 1908 Persistent patency of the ductus arteriosus. Am. J. Med.
SC.,V O ~ .136, pp. 381-400.
WINTERNITZ,
M. C., R. M. THOMASA N D P. M. LE COnfPTE 1938 The Biology of
Arteriosclerosis. Baltimcre (Chas. C. Thomas).
PLATE 1
EXPLANATION OF FIGURES
l a n d 2 Open ductus arteriosus. Thoracic viscera as seen through a n opening
in the left side of the chest. The open ductus (D) appears as a continuous vessel
from the pulnioiiary artery ( P ) to the aorta ( A ) . The aorta near the point of
cntrance of the ductus is not clearly seeii as it is covered by overlying tissue, but
is visible caud:alward, being crossed by a dark vein. A small part of the pulmonary
artery beyond the ductus can be seen going posteriorly and inferiorly in figure 2.
From fetal guinea pig near terni. Photograph ( X 2 ) . (Note: The heart is being
displaced to the right with a probe for the purpose of photographing the ductus
clearly.)
3 and 4 Closed ductus arteriosus. View and lettering similar t o figure 1. The
ductus has closed following inflation of the lungs with air, and appears much
narrower than the trunk of the pulmonary artery. From fetal guinea pig near
term. Photograph ( X 2 ) . Tissue has been dissected froin the front of the junction
of aorta and ductus.
364
CLOSURE OF DUCTUS ARTERIOSUH
J. A T I A E N KENNEDY A N D SAM
1,. CLARK
PLATE 1
PLATE 2
E l P L 4 N A T I O N OF FIGURES
5 Open ductus arteiiosus. Cross srction taken through ductus (D) near junction
with pulinonwy artery (P). Note relative thickness of walls of ductus and pulmonary artery. Tlie lumen of the duetus is this size throughout its length as stion-n
by serial scrtions. Grossly this ductus appeared like that in figures 1 arid 2 .
From fetal guinea pig near t e r m H. arid E. stain ( X 60).
6 Closed ductus arteriosus. Tlic tissue mas fixed inimediately after closure.
This ductus is ompa parable in its stage of development to t h a t in figure 5 and
grossly appeared like those shonn iii figures 3 and 4. Tlie lumen is practically
obliterated and is represcntrd by a small slit. From fetal guinea pig near term.
H. and E. stain ( X 6 0 ) .
7 Scction through junction of ductus (I)) and aorta ( A ) . The projectioii of
tissue into tlie aoitic lumen ou tlie cephalic border of the opening is a t tlie upper
ninrgin of the ductus. It appears as a doubliiig of the vessel wall rather than as
n valve. From fetal guinea pig near term. Longitudiiial section H. and E. stain
( X G O ) . For gross appeaiance compare figure 8.
8 Opening of ductus arteriosus into aorta. The aorta has been laid open. A
short crescentic fold is present but no real valve. This lip probably is indicative
nf tlie oblique entrance of tlic ductus into the aorta. The ductus was closrd and
its narroniiess can be compared nitli the trunk of the pulrrioiiary artery ( P ) . From
3 guinea pig fetus near term a f t e r fixation in formalin. Photograph ( x 4 ) .
366
CLOSURE OF DUCTUS ARTERIOSUH
J. A T I A E N KENNEDY A N D SAM
PLlTE 2
1,. CLARK
367
PLATE 3
E S P L ~ . I S A T l O SO F F I G U R E S
9 1Vt:igei.t staiiicd lonpitudinnl section through one nall of an open ductus
:irteriosos of a guinea pig fetus iie:ii' term, sliowiiig its junction wit11 t.lie liuln~onarg
:trt,cry on the right. Kote tlic sinallrr qnantit.y of clastic? tissur in the ductus and
the slimit ol)liquc linc indicating the :ihrupt.cliaiigc in liistologienl structurc ( X 6 0 ) .
10 Lig:imentnni arteriosuni of a 7-clay-old giiiiirs pig. Tlie clnetus w a s seetioiled
Icngthwisc ;it its jonetioii with t.lie :iort.a, showing the aliscilce of lnincii %it11 proliferation of cells near the :tort:&:lad the lioiiiogc~ieousmaterial i n t.he axis of the
fonncr ductus. No lumen is liresent. Tlie sniall c1e:ir area in the ductus is an
artcfnet. The strurtural e1i:ir;ictrristics of the wall of tlic ductus a r e still risible.
H. mid E. stain ( X (i0).
11 I,igmiieiitum arteriosurn of n 30-dny-old guinea pig. The strncturr is nlniost
mholly fibrous tissue though n little rnrootli muscle is still v i s i l k . H. and E. ( x 6 0 ) .
368
CLOSCRX OF DUCTUS ARTEHLOYUS
J. ALTAN K E N N E D Y
AWD
S A M L. C I A l t l i
369
PLATE 1
EXPIANATIOX OF FIGURES
1 2 Branching nervc fiber and endings in the wall of the ductus a t the point of
junction with the aorta. From a guinca pig fetus near term. Pyridin-silver ( X 320).
1 3 Branching nerve fibers in the aortic depressor area in the wall of aorta just
cranial to the junction of aorta and ductus. Duc to the darkness of the background
in this section the nerve fibcrs did not photograph with the contrast actually visible
in the section. The black n e n e fibers i n tlie lower riglit corner are n part of the
aortic nerve alongside the aorta. From a guinea pig fetus near term. Pyridiiisilver ( X 2 3 0 ) .
1-1, Portion of thc wall of the ductus artcriosus near the aorta showing sections
of nerve fibers in tlir incdia. From a guinca pig fetus near term. Pyridin-silver
( X 640).
370
CLOSURE OF DUCTCJS ARTERIOSUS
I’IATE 4
J A121 06 K h I N E D Y AN11 BAS[ 1, CLARK
371
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