The elaboration of the sex impulses and desires into the purposes of marriage, the repression into lifelong continence and chastity, forms one of the most marvelous of chapters in the psychological history of man. The desire for sex relationship of the crude kind is very variable both in force, time of appearance and reaction to discipline and unquestionably arises from the changes in the sex organs. Both to enhance and repress it are aims of the culture and custom of each group, and the lower groups have given actual sexual intercourse a mystical supernatural value that has at times and in various places raised it into the basis of cults and religions. Repressed, hampered, canalized, forbidden, the sex impulses have profoundly modified clothes, art, religion, morals and philosophy. The sex customs of any nation demonstrate the extreme plasticity of human desires and the various twists, turns and customs that tradition declares holy. There have been whole groups of people that have deemed any sexual pleasure unholy, and the great religions still deem it necessary for their leaders to be continent. And the absurdities of modesty, a modified sex impulse, have made it immoral for a woman to show her leg above the calf while in her street clothes,[1] though she may wear a bathing suit without reproach. [1] This is, of course, not quite so true in 1921 as in 1910. Whatever a desire is basically, it tends quickly to organize itself in character. It gathers to itself emotions, sentiments, intelligence; it plans and it wills, it battles against other desires. I say IT, as if the desire were an entity, a personality, but what I mean is that the somatic and cerebral activities of a desire become so organized as to operate as a unit. A permanent excitability of these nervous centers as a unit is engendered, and these are easily aroused either by a stimulus from the body or from without. Thus the sex impulse arises directly from tensions within the sex organs but is built up and elaborated by approval of and admiration for beauty, strength and intelligence, by the desire for possession and mastery, by competitive feeling, until it may become drawn out into the elaborate purpose of marriage or the family.