74 
THE VETERINARY SOENCE 
of the hymen is called the vagina. This passage, in structure, 
resembles the womb, but is not so strong. There are 
numerous glands situated along the inner coat or lining which 
secrete a fluid to lubricate it. The principal use of this organ 
is to guide the penis during sexual intercourse, and at the 
time of foaling serves as a passage for the foal. That part of 
the passage behind the hymen is known as the vulva. It is 
about four inches long and about two or three inches high, 
varying according to the size of the mare. In front, it is 
separated from the vagina by the hymen membrane. It 
resembles the vagina in structure, and is also provided with 
little glands in its inner coat to secrete a fluid to lubricate 
the passage. At the back part of the vulva, or around the 
outside, is what is known as the lips of the vulva, one on each 
side of the opening. The outside of the lips is covered by a 
very fine skin. Just below the skin, they consist of erectile 
tissue, which is the same kind of tissue as that of the penis 
of the horse. This tissue is found more abundantly in the 
lips of the vulva 6f the young mare than in those of an old 
mare. The opening between these lips is situated just below 
the anus, or the opening where the back bowel ends. At the 
back part of the vulva, on the under side, is an opening, or 
hole, about large enough for the passage of a man's finger. 
Through this hole the tube leading from the bladder enters 
into the passage and allows the urine, or water, to pass into 
the vulva, through which it runs out of the body. The 
clitoris is situated on the under side of this passage, just 
inside the lips. It can be seen in the mare when she works 
the vulva after passing water. Just below the clitoris are 
found two or three small glands which secrete the fluid that 
passes away when the mare is horsing. 
13. Mammary Glands. — Mammary glands, or what is known 
as the mare's bag, are two in number, situated between the thighs, 
young animal. In the young marc they are very small, but after 
the mare is with foal a few months these glands begin to get 
large, until at foaling time they attain their largest size. They 
are covered outside by a thin, smooth skin. The substance 
of them consists of small glands and tubes — the glands 
secrete the milk from the blood, while the tubes retain or 
hold the milk until it is drawn away from the bag either by 
milking or by the young animal's sucking. During the time 
ol suckling the young, the glands are larg^y supplied with 
