The human ovaries begin to prepare themselves for their life work when the girl is about eight years of age. When they are ripe, or ready to perform this duty, the girl menstruates for the first time. This is known as the age of "puberty," which implies that she has developed, passed from girlhood into womanhood. After having reached the age of puberty it is possible to become a mother. THE AGE OF PUBERTY.--There is no fixed age at which the first menstruation takes place. Some girls develop quicker than others,--a condition that depends upon the health and type of girl. A strong, robust, full-blooded girl will menstruate at an earlier age, than will a sickly anemic girl. The average age is fourteen years, though there is no reason to worry if a girl does not menstruate for a number of years later. In warm climates the age of puberty is from two to four years earlier than in more temperate climates. THE FUNCTION OF THE OVARY.--Just what takes place in each ovary when it is ripe is best explained by likening an ovary to an orange,--though of course the ovary is very much smaller than an orange, as was previously noted. If you make a cut in an orange and squeeze it, you express some of its juice and most likely you will also express one or more seeds. The seeds of the ovaries are called "ovules," and the process by which it expresses them is called "ovulation." Of course there is no actual squeezing of the ovary,--the ovules grow in the ovary, and as they ripen they come to the surface, and when actually ripe, the part of the surface of the ovary to which they come, opens up (like a flower unfolding when in bloom), and they fall out. The ovule we may regard as the human female egg, and one ripens and falls out every twenty-eight days. When the egg falls out of the ovary it falls into the tube which carries it into the womb. This tube you will remember is called the fallopian tube. The ovule or egg is now in the cavity of the womb where we will leave it for the present.