VAS DEFERENS.--These tubes are two in number and are situated just behind the spermatic cords. They are about an eighth of an inch in diameter and quite hard. They carry the semen up the back part of the spermatic cord through the inguinal rings, before mentioned. They pass backward and upwards, one on each side, to the upper part of the bladder, where they empty into two small pouches or sacs, called the vesiculae seminales. These store up the semen as it is secreted by the testicles, and when full present the appearance of a pear. VESICULAE SEMINALES.--These sacs or pouches are situated at the upper side, over the neck of the bladder, one on each side. They have the vas deferens emptying into them at the front end, while at the back end of each is a small opening that leads out into another small tube which passes backward and empties into the urethra, mentioned before as carrying the urine out from the bladder. These sacs or pouches store up the semen or sperm of the horse. During sexual intercourse, these pouches contract and force the semen through the little tubes mentioned out into the urethra, leading down through the penis. The Penis is the main organ of sexual intercourse. Its substance is formed of what is known as erectile tissue, which under certain circumstances becomes enormously distended with blood. Passing up the under side there is, what has already been mentioned, the urethra, or the tube, which carries the urine out of the body, and also in the act of intercourse carries the semen. This is used for two purposes, as we have already mentioned. The Sheath is a loose process of skin which passes downward from the scrotum, generally from about five to six inches, according to the size of the animal. It is attached to each side, leaving a hole or opening in the center through which the penis passes. The outside of the sheath is covered by a thin, delicate skin similar to that of the scrotum. It is lined inside by a membrane containing many small glands, which secrete a thick, dark fluid to lubricate this passage. Sometimes this fluid collects in here and has the appearance of tar. This is important, for when it collects to a large extent the sheath should be washed. The Semen or sperm of the horse is a light fluid, which, when examined under a microscope is found to contain small objects called spermatozoa. These move about, and when in the womb meet the ovum of the female, which is secreted by a gland called the ovary. When these two small objects unite, they form the foetus, or what may be called the animal in its first stage of development. FEMALE GENITAL ORGANS. The female genital organs, or the organs of the mare, are very much different from those of the horse. They are known as follows: The ovaries, the fallopian tubes, or tubes which carry the ovum from the ovaries to the uterus or womb, the uterus or womb, the vagina, and the vulva.