Like the testicles in man, so the ovaries in woman are the essential sexual organs. They are the fundamental organs, without which the other sexual organs are useless. Also like the testicles in man, the ovaries have two distinct functions, manufacturing two distinct substances. One function is to manufacture eggs; this, called the ooegenetic or egg-producing function, is its _racial_ function; without it the race could not perpetuate itself. But the ovary has also an _individual_ function. Besides the ova, the ovary manufactures what we call an _internal_ secretion which is absorbed by the blood, and which is of the greatest importance to the woman herself. While the manufacture of ova begins only at puberty, with menstruation, and closes at the menopause, the manufacture of the internal secretion lasts throughout the woman's entire life. This secretion, which consists of various chemical substances, has a tremendous influence not only on the development of the woman's body, but also on her feelings. First of all it is necessary for the development of the woman's special characteristics, or _secondary sexual characters_. Without that internal secretion of the ovaries, a woman would look more or less like a man; she would not develop her beautiful rounded form, her pretty long hair, her breasts, her broad pelvis, her feminine voice, etc. _Second_, the secretion is necessary to the proper development of her other sexual organs; if the ovaries are cut out, then the uterus and the vagina and even the vulva shrivel up. _Third_, it is that internal secretion that excites in woman sexual desire and makes her enjoy relations with the male sex. If the ovaries are cut away, particularly if it is done early in life, the woman has no sexual desire and no enjoyment. _Fourth_, it contributes to the general health, wellbeing, energy, and mental alertness of the woman. You see the importance of the internal ovarian secretion, and you will readily understand why, when the ovaries are removed by operation, the woman, particularly if she is young, undergoes such marked changes. It is because we recognize now the great importance of the ovaries that we always, when operating on diseased ovaries leave at least a small piece of ovary, if at all possible.