Quality of pleasure, symptoms of pleasure, orgasm, symptom of after-lust, intensity of libido, the senses in its service, inhibition of libido, duration of copulation, post-orgastic stage. PART V: PSYCHOLOGY OF SEX. _Chapter 10—Psychology of sex-attraction._ Nature of the instincts, children’s affections, puberty, sex instinct in animals, mechanism of sex activity, emotions of puberty. _Chapter 11—Development of reproductive impulse._ Conjugation in unicellular animals, in metazoa, binary fission, budding, sporulation, conjugation in chilodon, in monads, hermaphrodites, self-fertilization, in phanerogamous plants, genitals of plants, sex differentiation, erotic chemotropismus in fishes, birds, mammals, attraction of mates, permanent mating, protection of the young, monogamy. _Chapter 12—Sensual love._ Egotism of sensual love, fondness, attachments, hatred. _Chapter 13—Sentimental love._ Conscious altruism, mental characters, psychic qualities, true friendship, love and passion, development of individual love, characteristic of the ideal woman’s love, obstructions in the development of love, tension at puberty, reasons for the disturbances in love’s development, disillusion of sensuality. _Chapter 14—Eros and libido._ Emotions of Eros and libido, in men, and in women, jealousy, transcendental attraction, two desires of Eros, difference in the two sexes, emotion of jealousy, its causes, vanity, woman’s former love-affairs. PART VI: PATHOLOGY OF SEXUALITY. _Chapter 15—Paradoxia._ Sexual desires in the old, in infants, causes of early masturbation. _Chapter 16—Anaesthesia._ Etiology of impotence in male, chain of sex-act, satyriasis, nymphomania, troubles in bladder, in menstruation, nervous debility, consensualism, break in chain, continence and impotence, woman’s sexuality, impotence in women, clitoris sexuality, excesses in copulation, hysteria, practice of withdrawal, four impotencies in males, aspermia, azoospermia, four types of impotence of copulation, atonic impotence, partial impotence, premature ejaculation, symptoms of the impotent, pollutions, paralysis of bladder, urinary symptoms, female impotence, frigidity, sterility, impotence of libido, orgasmus retardatus, nymphomania, orgasmus praecox, diminished frequency. _Chapter 17—Hyperaesthesia._ Mixoscopy, its emotions, obscene sights, erotomania, in men, in women, satyriasis, nymphomania, priapism, masturbation, in animals, in women, incest in men, in women. _Chapter 18—Paraesthesia._