598 GENITAL ORGANS OF THE MARE 
The stroma of the ovary (Stroma ovarii) is a network of connective tissue. In the 
meshes of the stroma there are (in young subjects) numerous ovisacs or folliculi 
odphori, containing ova (Ovula) in various stages of development. The immature 
ovum is surrounded by follicle cells; those more advanced in development are 
enclosed by several (5-8) layers of follicle cells, forming the stratum granulosum, and 
by a condensation of the stroma termed the theca folliculi; within the theca is a 
quantity of fluid, the liquor folliculi. At one point the follicle cells are heaped up as 
a sort of mound (Cumulus oéphorus), in which the ovum is enclosed. Such saes 
are termed folliculi o6phori vesiculosi;! they enlarge as they mature, becoming 
visible to the naked eye as vesicles with a diameter of a centimeter or more. When 
fully developed, the follicles are superficially situated, and often project slightly 
from the surface of the ovary. At intervals follicles rupture and their contents 
escape. This process, which sets free the ovum, is termed ovulation; it 
takes place in the mare only 
at the ovulation fossa, and 
oecurs during the periods of 
cestrum. 
3 
~N 
~~ 
\‘ 
The structure of the ovary of 
the mare is peculiar and differs from 
that of other animals in the fact 
that it does not consist of a cortex 
(zona parenchymatosa), im which 
the follicles are situated, and a me- 
dulla (zona vasculosa), which con- 
tains the vessels and nerves. This 
arrangement is present in the foetus, 
but later the follicles become dis- 
tributed throughout the interior of 
the gland, and the vascular zone is 
superficial. 
After rupture of a follicle, its 
cavity is partly occupied by a blood- 
clot, constituting what may be 
termed a corpus rubrum. By prolif- 
eration and enlargement and fatty 
Fic. 532.—Scuematic REPRESENTATION OF CHANGES IN OVARY OF 
Mare FROM Farrar tro ADULT State. (After Born.) 
The changes affect chiefly the free border (upper in figure) and 
the extent and form of the area covered by germinal epithelium (4). 
1, Peritoneum (broad ligament) ; 
tube; 4, 
2, ligament of ovary; 3, fimbria of 
germinal epithelium; 45, vessels, which reach the 
The latter represents the hilus, 
while the deep depression at the free border is the ovulation fossa. 
(Ellenberger, in Leisering’s Atlas.) 
uterine 
ovary at the attached border (6). 
In the new-born foal the ovaries are large and oval in form. 
is covered by germinal epithelium, which extends over a large part of the surfaces also. 
changes, the follicle cells are trans- 
formed into lutein cells, forming a 
yellow mass known as a corpus lu- 
teum. If impregnation takes place, 
the accompanying increase in vas- 
cularity of the organs may cause 
the corpus luteum to reach a large 
size; if impregnation does not oc- 
eur, it is much smaller, and is 
sooner replaced by sear tissue, form- 
ing the corpus albicans s. fibrosum. 
The free border is convex and 
This area 
is distinguishable by its dull gray appearance from the peritoneal surface, which has the usual 
smooth glistening character. 
Waldeyer the margo limitans periton:zei. 
until it assumes its definitive curved shape. 
lation fossa. 
which is the same as that of the testicle. 
The limit of the peritoneal epithelium is a distinct line, termed by 
As growth proceeds the ovary gradually becomes bent 
The germinal epithelium is then limited to the ovu- 
The ovary migrates somewhat during development from its primitive position, 
Tn old animals the ovaries commonly consist largely of fibrous tissue, in which 
there are often cysts of various sizes. 
The ova, present in enormous number at 
birth, have then been extruded, or destroyed by phagocytic action or degeneration. 
Vessels and Nerves.—The arteries of the ovary are derived from the ovarian 
artery. 
are large and numerous. 
The artery is relatively large and is flexuous; it reaches the attached 
border of the ovary by passing between the layers of the mesovarium. 
They form a plexus somewhat like that of the spermatic 
The veins 
1 Also known as Graafian follicles. 
