_The vagina_ is a musculo-membranous canal that leads from the womb. In the
mare and cow it is about one foot in length. Its function is to take part
in copulation and parturition.

_The vulva_ is the external opening of the maternal passages. It shows a
vertical slit enclosed by lips, and interiorly it forms a passage that is
continuous with the vagina. This passage is about six inches long in the
larger animals. The different features that should be noted are the
clitoris, a small erectile organ located at the inferior portion of the
opening, the meatus urinaris, the external opening of the urethra, situated
in a depression in the floor of the vulva, and the hymen, an incomplete
membranous partition that may be found separating the vulva from the
vagina.

_The mammary glands or udders_ secrete the milk that nourishes the young.
The glands vary in number. The mare has two, the cow four (Fig. 17), the
ewe two and animals that give birth to several young, eight or more. Each
gland is surmounted by a teat or nipple. The glandular tissue consists of
caecal vesicles that form grape-like clusters around the milk tubules. The
milk tubules from the different portions of the gland converge and form
larger tubules that finally empty into small sinuses or reservoirs at the
base of the teat. Leading from these sinuses are one or several milk ducts
that open at the summit of the teat.

GENITAL ORGANS OF THE MALE.--The genital organs of the male are the
testicles, the ducts or canals leading from the testicles, the seminal
vesicles, the glands lying along the urethra, and the penis.

[Illustration: FIG. 17.--Photograph of model of udder of cow: milk duct;
milk sinuses; and glandular tissue.]