Every twenty-eight days or so a woman, from the time she is about thirteen or fourteen till she is about fifty, has a slight flow of blood from the uterus, which is called menstruation. The reasons for this are not wholly understood, but it is supposed there is an extra supply of blood provided periodically for the growth of a baby, but when there is no baby starting to grow, the blood is not needed so it flows away (about once in four weeks). Often the unfertilized ovum is carried away with it, but the two things do not necessarily happen at the same time. Menstruation lasts from three to five days and young girls sometimes have pain then and feel languid and “unwell.” If so they should be quieter than usual and avoid cold baths and getting their feet wet. But menstruation is not an illness, and a girl in perfect health finds it only a slight inconvenience.
The ovaries not only produce the egg, but they also produce a secretion that is absorbed by the blood and which is most necessary in the development of a girl into a woman. It has an almost magical effect in adding the specially womanly qualities to the body and character.
Looking at Plate 2, you will see the man's sex machinery. The testicles are to a man what the ovaries are to a woman. They are two sacs held in a bag of rather thin loose skin called the scrotum, and it is here that the sperm (spermatozoa) or germ of life grows. Just how no one really knows. The spermatozoa are very tiny and the testicles hold many thousands of them. Under the microscope they show a sort of head and tail like a pollywog. They are very much alive and move by a rapid wiggling of the tail part.
Leading from each testicle is a tube called the vas deferens, through which the sperm goes at the time of the sex act on its way out to meet the ovum in the woman's body. On the way it is joined by two other liquids, one secreted by the seminal vesicles (of which there are two) and the other by the prostate gland. These three liquids together form the semen, which at the times of sexual excitement is forced out through the penis into the vagina of the woman.
You will notice that the woman has separate tubes for the urine (waste water) and the sex function, but the man uses the same tube for both: that is, in the woman the bladder which holds the urine is emptied by a separate tube, the urethra, while in the man the urethra not only empties the bladder, but it also carries the semen.
The use of the seminal vesicles and the prostate gland is to supply a means of nourishment for the spermatozoa until they reach the ovum, which may not be for several days after the semen is expelled into the vagina.
Then there are two small glands called Cowper's glands, which make the passage in the penis alkaline, as the spermatozoa can only remain alive in an alkaline secretion and the urine is acid, so always just before the penis forces out the semen, the secretion from Cowper's glands goes ahead to protect the sperm from being destroyed by any remaining traces of the acid urine.
At the end of the penis is a fold or cap of skin, the prepuce, which the doctor often removes for the sake of the boy's health, a process called circumcision, and it is a great relief to boys whose prepuce or foreskin is too tight as to make difficulty in keeping clean. All Jewish babies are regularly circumcised, a custom dating way back to Bible times.
There is a constant internal secretion from the testicles of a man just as from the ovaries of a woman, and it has the same beneficial effect on the whole being. It makes a boy what we call manly or virile. The value of the internal secretions of the sex organs in both boys and girls is so great that for that reason, if for no other, the whole sex machinery must be kept in perfect health.
Boys have a certain discomfort to bear which is difficult for them just as menstruation is difficult for girls. But by knowing the meaning of things and by taking care of themselves, they need not be seriously troubled by it. Every once in a while as they are growing up, but before they are old enough to really fall in love and marry and have children, boys feel a sort of stirring of the sex organs—sometimes so much so that it makes them quite uneasy and anxious for relief. The thing to do is to keep as calm as possible and keep very busy and very healthy. Then the discomfort will not be too great, and nature will usually bring relief by letting the accumulated semen pass off during sleep. This is called a seminal emission, and is perfectly harmless. Sometimes a vivid sexual dream comes with it, but that too will do no harm, unless a boy lets his mind dwell on it till the excitement grows unnatural. This emission may happen every two weeks or so, but it is not a regular thing. Boys are sometimes alarmed and fear their sex machinery is out of order, but it is a perfectly natural thing, and only means that the organs are relieving themselves of the extra secretions that are not needed till the time comes for the real sex relation.