[Illustration:
FIG. 407.—LATERAL VIEW OF GENITAL ORGANS AND ADJACENT STRUCTURES OF
MARE.
The removal of the other abdominal viscera has allowed the ovaries and
uterus to sink down, whereas they are normally in contact with the
roof of the cavity in the non-pregnant subject. _1_, Left ovary;
_2_, Fallopian tube; _3_, left cornu uteri; _4_, right cornu uteri;
_5_, corpus uteri; _5′_, portio vaginalis uteri, and _5″_, os uteri,
seen through window cut in vagina; _6_, broad ligament of uterus;
_6″_, round ligament; _7_, vagina; _8_, labia vulvæ; _9_, rima
vulvæ; _9′_ superior commissure, and _9′_, inferior commissure of
vulva; _10_, constrictor vulvæ; _11_, position of vestibular bulb;
_12_, ventral wall of abdomen; _13_, left kidney; _14_, left ureter;
_15_, urinary bladder; _16_, urethra; _17_, rectum; _18_, anus;
_19_, _19′_, unpaired and paired parts of sphincter ani externus;
_20_, retractor ani cut at disappearance under sphincter; _21_,
suspensory ligament of anus; _22_, longitudinal muscular layer of
rectum; _22′_, recto-coccygeus; _23_, constrictor vaginæ; _a_,
utero-ovarian artery, with ovarian (_a′_) and uterine (_a″_)
branches; _b_, uterine artery; _c_, umbilical artery; _d_, ischium;
_e_, pubis; _f_, ilium. (After Ellenberger, in Leisering’s Atlas.)
]
The =ovaries= (Ovaria) of the mare are bean-shaped, and are much smaller
than the testicles. Their size varies much in different subjects, and
they are normally larger in young than in old animals; one ovary is
often larger than the other. They are about three inches (ca. 7 to 8
cm.) long and an inch to an inch and a half (ca. 3 to 4 cm.) thick. The
weight is about two and a half to three ounces (ca. 70 to 80 grams).
Each presents for description two surfaces, two borders, and two
extremities or poles. The =surfaces= are termed internal and external
(Facies medialis, lateralis); they are both smooth and rounded.[149] The
=attached= or =mesovarial border= (Margo mesovaricus) is convex. It is
inclosed in a part of the broad ligament termed the mesovarium; the
vessels and nerves reach the gland at this border. The =free border=
(Margo liber) is marked by a notch which leads into a depression, the
=ovulation fossa=. The =tubal= or =anterior extremity= (Extremitas
tubaria) is rounded, and is related to the fimbriated end of the uterine
or Fallopian tube. The =uterine= or =posterior extremity= (Extremitas
uterina) is also round, and is connected with the horn of the uterus by
the ovarian ligament.
The ovaries are situated in the sublumbar region of the abdominal
cavity, about a handbreadth behind the corresponding kidney. They are in
contact with the lumbar wall of the abdomen, and are commonly about two
or three inches (ca. 5 to 7.5 cm.) from the median plane. The distance
from the ovaries to the vulvar orifice is about twenty inches (ca. 50
cm.) in a mare of medium size. The attached (mesovarial) border is
commonly directed toward the median plane, the free border laterally and
somewhat ventrally.
The position of the ovaries is not constant, but is subject to less
variation than might be expected from their mode of attachment. The
normal variations in the non-pregnant state are chiefly in a
transverse direction, and do not usually exceed two or three inches
(ca. 5 to 7 cm.). It is not at all rare to find the ovary deflected
medially, so that the external surface faces ventrally. In the
longitudinal direction little variation appears to occur. The right
ovary is usually about four or five inches (ca. 10 to 12 cm.), and the
left one about three or four inches (ca. 8 to 10 cm.), behind the
corresponding kidney. Thus they lie about in a transverse plane
tangent to the external angles of the ilia, i. e., through the fifth
lumbar vertebra. They may be about two inches (ca. 5 cm.) from the
extremity of the corresponding cornu of the uterus or in contact with
it. The right ovary commonly lies a little (ca. 2.5 cm.) further
forward than the left one. Except during pregnancy, they are normally
in contact with the lumbar abdominal wall, and do not hang down among
the adjacent viscera.
[Illustration: