Now in this process of producing a new life-form, the female is always the source of the egg, out of which the new creation is to come. This egg, however, is infertile of itself, and must be given life to, by mingling with its germ, an element which only the male can produce and supply. This element is technically known as a sperm, or a spermatozoa. Its function is to fertilize the dormant germ in the egg produced by the female, and thus to start a new and independent life-form. This life-form, thus started, grows according to the laws of its becoming more and more, until, at the expiration of a fixed period, which varies greatly in different animals, it becomes a complete young individual, of the nature and kind of its parents. The fertilization of the ovum in the female is called conception; its growing state is called gestation, and its birth, on becoming a separate being, is called parturition. In its growing condition, and before its birth, the new young life form is known as the foetus. Now it is the fertilization of the ovum in the female (and from now on, it is only of the male and female in the human family that mention will be made) by the male, in the woman, by the man, that is of supreme interest and importance to both the parties concerned in producing this result. How this is brought about is substantially as follows: As already stated, the infertile ovum, or egg, is produced by the woman. Such production begins at what is known as the age of puberty, or when the hair begins to grow upon the pubic parts of the female body. The time of the appearance of this phenomenon in feminine life varies from the age of nine or ten years to fifteen or sixteen. The average, for most girls, is fourteen years of age. At this time the formation of ova, or eggs, in the female body begins, and it continues, in most women, at regular intervals of once in twenty-eight days, except during pregnancy and lactation, for a period of about thirty years. During all this time, under favorable conditions, it is possible for the ovum produced by the woman to become fertilized, if it can meet the sperm of the male. In a general way, this meeting of the infertile ovum of the woman with the sperm of the man can be brought about, as follows: