A resemblance to heat or rut in animals, who exhibit the sexual impulse only at definite periods, those at which the ovules ripen, is manifested in females of the human species only in so far as there is during menstruation a more intense sexual sensibility; but the limitation of the sexual impulse to definite periods, and its close association with reproduction, are not found in women. Education and morality impose artificial limitations on the sexual impulse in women, whilst nature endows this impulse with a coercive power, a fact recognized by thinkers of all times and all peoples. Thus, _Buddha_ wrote: “The sexual impulse is stronger than the ankus with which the wild elephant is controlled, it is hotter than flame, it is like unto an arrow driven into the spirit of man.” In a similar sense _Luther_ writes: “He who wishes to restrain the impulse of nature and not to allow it free play, as nature will and must, what does he do but this, to insist that nature shall not be nature, that fire shall not burn, that water shall not wet, that man shall neither eat, drink, nor sleep.” _Schopenhaur_ describes the sexual impulse as “the completest outward manifestation of the will to live, the concentration, that is to say, of all wills. * * * The affirmation of the will to live concentrates itself in the act of generation, and this act is its most determined expression.” _Mainländer_ in his _Philosophy of Deliverance_ makes the following statement: “In the sexual impulse lies the centre of gravity of human life. To nothing does man devote a more earnest attention than to the business of generation, and in the pursuit of no other aim does he concentrate the intensity of his will in so striking a manner as in the performance of the act of generation.” _Debay_ similarly insists on the strength of the sexual impulse, saying: “The union of the sexes is one of the great laws of nature; to that law men and women are subordinated as completely as all other creatures, they cannot escape its operation.”