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The development of the periovarial sac in the white rat.

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Laborutory of Histology and Embryology, Depaytment of Zoology,
Cornell Uiiiversity, Ithacu, New Pork
I n certain mammals, the infundibulum of the oviduct opens
into a peritoneal capsule, the periovarial sac or bursa ovarii,
which surrounds the ovary and has usually no communication
with the coelomic cavity. This condition is found in such
animals as the rat (Ellenberger and Baum, '26; Greene, '35),
mouse (Fischel, '14; Powierza, '12 ; Sobotta, 1895), weasel,
shrew, wolf (Gerhardt, '04), and otter (Weber, 1826).2 Among
the majority of mammals, however, the periovarial sac is
found to vary widely in the extent of its development (Zuckerkandl, 1897 ; Gerhardt, '04 ; Owen, 1868). In the dog, bear, sea
lion and racoon, only a small opening exists in the wall of the
sac. A large number of animals, such a s the cat, hyena, guinea
pig, mole, pig, possess a wide open capsule. There is just
an indication of this structure to be found in man; it is totally
absent in whales.
Gerhardt ( '04) believes that the comparative lack of a
periovarial sac is a factor in the relatively limited number
The author wishes t o express her appreciation to Dr. H. €3. Adelmann €or
the suggestion of the problem and for his assistance during the course of the
* In general, members of the class Chiroptera hare a small opening in the wall
of the periovarial sac (Robin, 1881). In the genus Vesperugo, however, Gerhardt
('04), MacLoed (1880) and Van Beneden (1880) find that the capsule is closed.
With these findings, Robin (1881) does not wholly agree.
of offspring produced by the human race. Indeed, a well
developed capsule is of considerable physiological importance
in the transport of the egg from the ovary to the oviduct as
shown by Sobotta (1895) and Kelly ('35). The former describes the mechanism for the transport of the egg; the latter
experimented with the effects of rupturing the capsule on litter
size, and found that when the capsule is ruptured, the number
of ofisprinp is apppreciably decreased.
It is an interesting fact that in spite of the large amount
of research on the anatomy and physiology of the female
I-eproductive system in recent ~7ears,there are relatirely few
references to the development of the periovarial sac. Zuckerkandl (1897) considers briefly the development of the sac in
a number of animals, particularly the dog and horse. I n the
latter animal, he suggests that the formation of the periovarial
sac accompanies a rounding up of the ovary, since the peritoneum of the future sac is attached to tlie two ends of the
gland in the regions of the ostium and of the ligamentum
ovarii proprium. Again in reference to the horse, Ellenberger
and Baum ( '26) believe the sac to be formed from the mesentery of the oviduct. I n this, they agree with the conclusion
reached by Gerhardt ('04) in his comparative work. Watson
(1877) and Owen (1868) find the sac to be formed by a reduplication of the broad ligament. Their observations concern
the hyena, and the r a t and mouse, respectively. IGngerp
( 'l7), working on the mouse, states that the periovarial sac
arises a s a fold of peritoneum which comes to enclose the
ovary and includes the oviduct between its layers. Powierzs,
( '12) tonclies briefly on tlie histogenesis of the capsule between
birth and maturity i n the mouse. Robinson (1887), who first
described the periovarial sac in tlie rat, finds it to be formed
from the broad ligament during a period in which the oviduct
is elongating. F r o m this survey of the literature, it may be
concluded 'that the periovarial sac arises in some way from
the mesentery of the oviduct O T uterus and that its formation
j s accompanied by the elongation of the oviduct. The exact
manner of its development has not been made very clear. It
was therefore considered worth while to investigate this
problem further, particularly in the white rat which is so
extensively used as a laboratory animal.
Ten series of rat embryos of 14-20 days were studied. Cross
sections of the upper urogenital system arid sagittal sections
of the abdominal viscera of rats from 1-8 days old were
made. The timing of' these rats was exact only within 24
Wax reconstructions of 18, 19, 194, and 20-day fetuses, and
of two 1-day rats were made from serial sections. One plasticine model of a 16-day fetus was constructed with the aid of
a camera lucida. Several adult rats were dissected. The
diagrams appearing in this paper were drawn from these
models after consulting the various series. Observations were
confined t o the left side of the body.
I n the adult rat, the periovarial sac is a double layer of
mesothelium completely surrounding the ovary and containing within its cavity the opening of the oviduct. iUedially,3
the ovary and siirrountling capsule are somewhat flattened.
Near the center of this flat'tened region, the edges of the sac
bend inward t o fuse with the periphery of a rather. extensive
core of connective tissue situated in the hilus of the ovary.
From this point, connective tissue Yadiates in several directions. The diaphragmatic l i g a m ~ n t loosly
attached t o the
dorsal body wall, leads anteriorly a s f a r as the diaphragm.
Laterally, connective tissue extends into the substance of the
ovary. A thick cord of tissue containing muscle fibers, the
ligamenturn ovarii proprium, runs caudally to the dorsomrdian surface of the uterus. This ligament forms an integral
The relationships of the ovary are not static, but vary to a certain extent
during the sexual cycle (Allen, '32).
' Throughout this study, it has been impossible to distiuguish exactly the
boundaries between the ligaments and mesenteries.
part of the median and posterior wall of the periovarial sac.
From the ligamentum proprium, strands of tissue extend
below and along the ventro-lateral and caudal walls of the sac
to the various loops of the oviduct. The infundibulum, opening into the periovarial sac, is closely fused to the lateral
surface of the ligament.
In its more generalized aspects, through the sixteenth day
of embryonic life, the development of the ovary and related
structures in the rat parallels that found in the human as
far as the 50 mm. stage (Keibel and Mall, '12). During this
period no traces of the periovarial sac are evident. On the
sixteenth day in utero (fig. l ) ,the ovary is an elongate body
with a slight medial concavity near its caudal end and with
its long axis corresponding roughly to that of the body.
Dorsally, the ovary is attached by a short mesentery, the
mesovarium, directly to the mesosalpinx, which extends medially to the body wall, and is bounded near its lateral edge
by the upper elid of the Miillerian duct or oviduct running
in the tubal ridge. The mesosalpinx arises, in part from the
peritoneum of the degenerating mesonephros, in part from
tlie tubal ridge.
The diaphragmatic ligament leads anteriorly from thc
cephalic ends of the mesosalpinx and mesovarium along the
dorsal body wall. The ligamenturn proprium runs from the
caudal end of the ovary and mesovarium posteriorly and
ends near that portion of the RIiillerian duct which later lies
approximately a t the boundary between the oviduct and
uterus. The oviduct begins at the ostium just anterior to
the cephalic end of the ovary and mesovarium and, in the
region where the mesovarium, diaphragmatic ligament and
mesosalpinx meet, is fused with them. From this point the
oviduct runs dorso-laterally for a short distance, then turns
caudally and slightly medially toward the posterior end of
the ovary (fig. l ) ,where it is again attached to the gland
by the ligamentum proprium. The primitive mesosalpinx and
the oviduct are and must remain in close association with
the two poles of tlic ovary. m7hen changes occur in the shape
of the reproductive gland, changes are also found to take
place in the configuration of the oviduct and mesosalpinx,
as well as in the closely associated ligaments.
Between the period just described and the day of birth,
the ovary assumes a rounded form. The first evidence of
change is found by the seventeenth day in a marked lateral
bending of the middle part of the ovary, leading to an apparent median shift of the two poles of the gland, particularly
the posterior pole (figs. 1, 2, 3, 4). Another series of movements is initiated about the nineteenth day in utero. Thc
antero-lateral half of the ovary (figs. 3, 4) moves ventrally
and slightly caudally, while the postero-median half shifts
ventrally and somewhat laterally toward it (figs. 5, 6). As
a result, a deep fissure is formed between the adjacent edges
of the approaching halves of the gland (figs. 5, 6). Viewed
ventrally, then, on the twentieth day in utero, the ovary is
divided into an antero-lateral and a postero-median lobe.
The ovary has begun to exhibit the more or less spherical
shape characteristic of the gland after birth (figs. 6, 7, 8).
While these changes in the shape of the ovary are occurring, the oviduct shifts across the surface of the gland, accompanied by the associated mesosalpinx. The mesosalpinx
becomes longer. Due to the medial movement of the two poles
of the ovary, beginning on the sixteenth day, the ostium and
the region of the duct attached t o the ligamentum proprium
are pulled toward the medial surface of the gland (figs. 1,
2, 3 ) . I n this way, a small part of the mesosalpinx is carried
on to the anterior and posterior portions of the ventral part
of the ovary. However, most of that mesentery still remains
dorsal (figs. 2, 3, 4). Thus, by the end of the nineteenth day,
the ovary is seen to lie in a very shallow cup formed by the
mesosalpinx and bounded laterally by the oviduct (fig. 4).
Between this period and the day of birth, as the antero-lateral
and postero-medial halves of the ovary approach each other
ventrally, the cephalic part of the oviduct is drawn candallp
There is considerable variation i n development in rats. The particular 20-day
rat fetus studied is less well developed than the 19+-day fetus.
across the bare surface of the gland (figs. 6, 7 , 8 ) . The ostium
is carried into the fissure between the two lobes of the ovary
(fig. 7 ) , and then caudally (fig. 8). The posterior part of the
oviduct, associated with the ligamentum proprium, shifts
cephalically toward the anterior segment (figs. 6, 7,8) so that
the main p a r t of the duct comes to form a n irregular loop on
the ventral surface of the gland. Thus, by the day of birth
(fig. 8), the mesosalpinx surrounds the gland almost completely, leaving only a small opening postero-ventrally within
the loop of the oviduct (fig. 8). Except for this space, therefore, the ovary is encapsulated on the first day post partem.
Although the periovarial sac is formed for the most part
from the mesosalpinx, the diaphragmatic ligament, ligamentum proprium and mesovarium also contribute a certain
amount of tissue to the sac. With the rounding up of the ovary,
just before birth, the mesovarium, which has shifted medially
by the eighteenth day in utero, becomes incorporated between
the two lobes of the gland (fig. 5). The region of the fissure
becomes the liilus and the tissue of the mesovarium forms
a plug of connective tissue in that region. Since the ud1ole
length of the mesovarium is continuous with the mesosalpinx,
this tissue in the hilus is continuous at its periphery with
the periovarial sac. As it leads cephalad from the mesovarium
on the day of birth, the diaphragmatic ligament forms a small
portion of the anterior wall of the capsule. In the same way,
the ligamentum proprium, running medially at the time of
birth (fig. 7 ) , but more and more posteriorly as the individual
develops after birth (fig. 8), contributes to the median and
caudal walls of the sac. a s the posterior portion of the
iriesovarium is carried toward the ceplialic part, between the
twentieth day in utero and the first day post partem, the
ligamentum propium comes into contact and fuses, near the
ostium, with the anterior end of the mesovarium and mesosalpinx, closing the capsule in this region (fig. 8). I n this
way, the ostium becomes attached to the ovary by the ligarnentum proprium a t the junction of the latter with the anterior part of the mesovarium. Below the ostium, the sac
47 1
is open for a short distance. Between the first and third
clays after birth the oviduct moves more caudally and begins
to coil, thus bringing the edges of the opening toward one
another. This process seems to occur last in the region of
the ostium. As the periovarial sac is completed, the infundibular end of the oviduct, which is now attached to the ovary
by the ligamentum proprium, is found to pierce the wall of
the sac and to open directly into its cavity. The periovarial
sac is found to be closed a s early as the seventh day after
birth, although the time is somewhat variable. Indeed, in
many of the mice examined by Icingery ('17) the final closure
does not take place.
It may be concluded that the periovarial sac is formed
principally from the mesosalpinx, as suggested by certain
earlier writers (see above). I n addition, there a r e certaii;
smaller contributions of tissue from the diaphragmatic ligament, ligamenturn ovarii proprium and, to a lesser extent,
the mesovarium. The ligaments a r e thus continuous with
the periovarial sac near the hilus, due to their intimatc
relation with the mesovarium which fills that structure. Although at 7 days after birth, when the periovarial sac is
complete, the oviduct has not yet attained the caudo-lateral
position characteristic of the adult, the periovarial sac itself
cliariges relatively little, except for histological differentiation,
from this time until maturity.
1.The periovarial sac is formed chiefly from the mesosalpinx
with contributions of tissue from the diaphragmatic ligament,
mesovarium and ligamentum ovarii proprium.
2. The development of the sac is closely correlated with
changes in the shape of the ovary.
3. Concurrent with the change of the ovary from an elongate
to a round body, the oviduct shifts across the free surface of
the gland, drawing with it, the mesosalpinx, which thus
furnishes the main part of the resulting periovarial sac.
4. A small space on the caudo-ventral surface of the gland
not covered by the sac on the day of birth is closed about the
seventh day by caudal movement and coiling of the oviduct.
a. During the process, the ostium becomes included within
the periovarial sac.
1932 Sex and internal secretions. 1 s t ed. p. 669. The Williams
and Wilkins Co. Baltimore.
W., AND H. BAUM 1926 Haiidbuch der Vergleichenden Anatomie
der Haustiere. 17“ Aufl. S. 562. J. Springer. Berlin.
A. 1914 Zur nornialen Anatomie uiid Physiologie der weiblichen
Geschlechtsorgane von Mus decumanus sowie iiber die experimentelle
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Bd. 45, S. 578.
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f . Naturwiss. Bd. 39, 5. 648.
GREENE,E. C. 1935 The anatomy of the rat. Trans. Am. Phil. SOC.(New
Series), vol. 27, p. 114, plate 137.
KELLY, G. L. 1939 Effect of opening the ovarian bursa on fecundity in the
albino rat. Anat. Rec., vol. 73, p. 401.
KEIBEL,F., AND F. MALL 1912 Manual of human embryology. First ed., vol. 2,
p. 752. J. B. Lippincott Co., Phila. and London.
H. M. 1917 Oogenesis in the white mouse. J. Morph., vol. 33, p. 261.
M. J. 1880 Contribution a l’btude de la structure de l’ovaire des
MammifBres. Arch. de Biol., vol. 1, p. 241.
OWEN, R. 1868 On the anatomy of the vertebrates. First ed., vol. 3, p. 676.
Longmans, Greeu and Co., London.
8. 1912 ITber Andernngen mi Bau der Ausfiihrwege des weiblichen
Geschlechtsapparates der Maus wahrend ihres postembryonalen Lebens.
Bull. Internat. de 1’Acad. des Sc. de Cracovie. C1. de Sc. Math. et
Natur., Serie B. Ann& 1913, p. 349.
ROBIN, M. H. A. 1881 Recherches aiiatomiques sur les Mammiferes de l’ordre
des Chiropthres. Ann. des Sc. nat. 2001. s6rie 6, T. 13, p. 111.
ROBINSON,A. 1 8 8 i The position and peritoneal relations of the mammalian
ovary. J. Anat. and Physiol., vol. 21, p. 169.
J. 1895 Die Befructung und Furchuug des Eies der Maus. Arch. f.
Mikr. Anat., Bd. 45, S. 15.
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1877 On the female generative organs of Hyaena erocuta. Proc.
2001. Soc. of London for 1877, p. 369.
WBBEZ, E. H. 1826 Ueber die Einhiillung der Eierstoke einiger Baugethiere in
einem vollkommen, geschlossen, voii der Bauchhaut gebildeten Sacke,
der der Scheidenhaut des Hoden ahnlieh ist. Meckel’s -4rchiv. f .
Anat. u. Physiol. 1826, S. 105.
E. 1897 Zur vergleichenden Anatomie dcr Ovarialtasche. Anat.
Hefte., Bd. 8, S. 705.
D, diaphragmatic ligament
Ms, mesosalpinx
Mo, mesovarium
P, liganientuiii ovarii proprium
Ov, ovary
Od, oviduct
1 Diagram of a plasticine rcconetructioii ( x 50) of the ovarp and associated
structures of a 1F-day r a t fetus; ventral view. Except f o r the cranial end, the
mesovarium lies dorsal to the ovary. The diaphragmatic ligament is anterior;
ligamentuni proprium, posterior; and the oviduct lateral to the ovary. The
orientatioii of all figures is the same. Sinall daslieq indicate that tlie material
lies on the other side of the structure. Large dashes indicate a cut edge.
2 Diagram of a w a s reconstruction ( X 50) of the orary and associated
structures of an 18 day rat fetus; ventral view. The edge of the mesovarium
appears medial to the ovary.
3 Diagram of a wax reconstruction ( X 50) of the ovary and associated
structures of a 19-day r a t fetus; ventral view.
4 Diagram of a wax reconstruction ( X 50) of tlie ovary and associated
structures of a 19-day rat fetus; ventral vier. This iiirlividual is further
developed than the prweding one.
5 Diagram of a wax reconstruction ( x 50) of the ovary and associated
structures of a 20-day rat fetus; ventral view. A fissure has appeared in the
substance of the ovary.
6 Diagram of a wax reconstruction ( x 50) of the ovary and associated
structures of a 19+-day rat fetus; ventral view. This individual is further
developed than the 20-day fetus.
7 Diagram of a wax reconstruction ( X 50) of the ovary and associated
structures of a rat killed early on the day of birth; ventral view. The periovarial
sac has extended laterally on t o the ventral surface of the ovary.
8 Diagram of a wax reconstruetion ( X 50) of the ovary and associated
structures of a r a t killed later on the day of birth. The periovarial sac is
almost completed.
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