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 secretion, or semen, of which the most vital constituents are the spermatozoa.

The testes are suspended in the scrotum by the spermatic cord, which consists of loops of muscular tissue, the vas deferens and blood vessels, all bound together by connecting tissue. Usually, the left testicle hangs a little lower than the right one, but the reverse is sometimes the case, and this is not to be considered an unfavorable condition. The veins of the cord are large and numerous and are arranged in a network called the spermatic plexus. When these veins are enlarged, the condition is known as varicocele.

The glandular tissue of the testes is composed of a number of lobules, made up of fine tubes, arranged in fibrous compartments. The fine tubes converge into larger ones, and finally emerge from the testicle by connecting with a larger coiled tube, called the epididymis. This is the beginning of the excretory duct, or outlet, of the testicles, and from this it is continued in a long single tube, the vas deferens.

During fetal life, while the unborn baby is in its mother's womb, the testes develop within the abdominal cavity, just below the kidneys. They gradually descend from this position until, at about the eighth month, they pass out of the pelvis and into the scrotum. An arrestment may occur at any point in this process of development, interfering with the descent of the testes. Or they may descend after birth. When this occurs, they usually descend in the course of the first week or two, but they may remain up in the pelvic cavity for several months before assuming their normal position.

Usually men with undescended testicles—a condition known as cryptorchidism—are sterile, although there are exceptional cases in which fertility is evinced. The sterility is due, not so much to the position of the testicles, but to the fact that when undescended they are generally imperfectly