The chief difference in these organs occurs in the kidneys, which in the ox are larger, and in place of being smooth, like those of the horse, are rough, resembling a bunch of grapes. The bladder and the urinary organs resemble those of the horse.
GENERATIVE SYSTEM OF THE HORSE.
Animals possess the faculty of reproducing or propagating their species, and this function may be non-sexual or sexual, the former being confined to certain lowly-organized classes of animals.
In all the higher animals the generation of a new being is dependent upon two individuals, a male and a female, the female furnishing a germ, or ovum, the male a fecundating fluid, or sperm, which animates the germ and renders it fit for development.
Both the ovum of the female and the sperm of the male are secretions of glands, which are termed the genital glands, male and female; and in either sex the generative system may be said to consist of these glands, with certain accessory organs. The act of coition brings the two secretions into contact.
We have two systems of genital organs to consider—the male and the female.
Male.—The genital organs of the horse are as follows: The scrotum or bag, the testicles, the spermatic cord, the vesiculae seminales or pouches which hold the semen or sperm, the urethra, the penis and the sheath.
The Scrotum is a sac or bag which contains the testicles. It is situated between the hind legs, and is covered on the outside by a very fine, soft skin. Passing up in the center under the sheath the scrotum is a well marked line in the skin called median raphe. This can be plainly seen when the horse is on his back. It continues up, gradually getting fainter until it reaches the anus. Under the skin are layers of white fascia or tissue which can be seen by cutting through the scrotum. There is a partition in the scrotum separating the two testicles. The size of the scrotum is affected very much by the weather. In cold weather its fibres contract, causing it to get very much smaller, while in warm weather the fibres relax, causing it to become very much larger. The scrotum contains, supports and protects the testicles.
The Testicles are the glands which secrete the semen or sperm. They are two in number, one situated on the left side and the other on the right. They are oval in shape, and are attached above to the spermatic cord. Before the animal is born the testicles are situated in the abdominal cavity and attached to the serous membrane which has already been spoken of in connection with that cavity. At or about the time of birth, there takes place what is known as the descent of the testicles into the scrotum. In their downward course they pass through a slit or small opening at the back part of the muscles of the abdomen, where they are attached to the under part of the hip bone. These slits or openings are known as the inguinal rings. They can be felt in the horse by pressing the fingers well up into the groins. The descent of the testicles is an important point to remember. If the testicle does not descend into the scrotum the horse is known as a ridgling. In this case the testicle is not found in the scrotum. At the front part of the testicle there is a small ridge called the globus major and at the back of it is another smaller ridge called the globus minor. Passing between these two ridges is another well marked ridge called the epididymis. These can be easily seen by examining the testicle after the animal is altered or castrated. The substance of the testicle is made up of small glands and fine tubes.
These tubes, as they pass towards the back of the testicle, form into larger tubes and finally unite to form one called the vas deferens.