It will thus be seen that in the varieties of degradation of our sexual powers, as well as in their use and ennoblement, it is the predominance of the mental or spiritual element in our nature which is the characteristic fact of human sex. The inventions and abuses of lust, as well as the use and guidance of love, alike prove the striking and important distinction which exists between the sexual organization of man and that of the lower animals. CHAPTER II _Equivalent Functions in the Male and Female_ In examining the characteristics of sex in Man under its dual aspect, male and female, Nature’s primary or rudimentary aim in establishing sex must be clearly recognised. This aim is the reproduction of the species. Pleasure in sexual congress is an incident depending largely on mental constitution. In the varying ranks of the animal creation it may or may not exist in connection with reproduction; for it is not essential to the one all-important dominating fact in nature, viz., parentage. Reproduction is accomplished in various ways in the widely differing ranks of living creatures. Man, owing to certain general resemblances of physical structure, belongs to the higher class of animals, the Mammalia. In this class the two factors necessary to reproduction, viz., ova and semen or sperm, exist in separate individuals. The ova or seed are formed in the ovaries, two small bodies placed within the pelvis of the female; whilst the sperm or vitalizing fluid is formed in the testes, two small bodies placed outside the pelvis of the male. The organs or parts which produce the ova and semen are strictly analogous in the two sexes. Each part in the female corresponds to a similar part in the male; and at an early period of existence before birth it is impossible to determine whether the sex of the embryo is male or female.